diff --git a/packages/pigeon/CHANGELOG.md b/packages/pigeon/CHANGELOG.md
index 32c08225e63..c916abf3f5a 100644
--- a/packages/pigeon/CHANGELOG.md
+++ b/packages/pigeon/CHANGELOG.md
@@ -1,6 +1,16 @@
+## 14.0.0
+
+* **Breaking change** [dart] Renames locally defined host API variables.
+  * [dart] Host api static field `codec` changed to `pigeonChannelCodec`.
+* [dart] Adds named parameters to host API methods.
+* [dart] Adds optional parameters to host API methods.
+* [dart] Adds default values for class constructors and host API methods.
+* Adds `isEnum` and `isClass` to `TypeDeclaration`s.
+* [cpp] Fixes `FlutterError` generation being tied to ErrorOr.
+
 ## 13.1.2
 
-* Adds compatibilty with `analyzer` 6.x.
+* Adds compatibility with `analyzer` 6.x.
 
 ## 13.1.1
 
@@ -159,7 +169,7 @@
 * [java] Adds a `GeneratedApi.FlutterError` exception for passing custom error details (code, message, details).
 * [kotlin] Adds a `FlutterError` exception for passing custom error details (code, message, details).
 * [kotlin] Adds an `errorClassName` option in `KotlinOptions` for custom error class names.
-* [java] Removes legacy try catch from async apis.
+* [java] Removes legacy try catch from async APIs.
 * [java] Removes legacy null check on non-nullable method arguments.
 * [cpp] Fixes wrong order of items in `FlutterError`.
 * Adds `FlutterError` handling integration tests for all platforms.
@@ -212,7 +222,7 @@
 
 ## 7.2.1
 
-* [kotlin] Fixes Flutter api int errors with updated casting.
+* [kotlin] Fixes Flutter API int errors with updated casting.
 
 ## 7.2.0
 
@@ -238,7 +248,7 @@
 
 ## 7.1.2
 
-* [swift] Adds error handling to sync host api methods.
+* [swift] Adds error handling to sync host API methods.
 
 ## 7.1.1
 
@@ -352,7 +362,7 @@
 
 ## 4.2.4
 
-* [kotlin] Fixes Kotlin generated sync host api error.
+* [kotlin] Fixes Kotlin generated sync host API error.
 
 ## 4.2.3
 
@@ -831,7 +841,7 @@ class Foo {
 
 ## 0.1.0-experimental.11
 
-* Fixed setting an api to null in Java.
+* Fixed setting an API to null in Java.
 
 ## 0.1.0-experimental.10
 
diff --git a/packages/pigeon/example/app/lib/src/messages.g.dart b/packages/pigeon/example/app/lib/src/messages.g.dart
index a07585d8bd0..59213e4ef2b 100644
--- a/packages/pigeon/example/app/lib/src/messages.g.dart
+++ b/packages/pigeon/example/app/lib/src/messages.g.dart
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -98,111 +98,118 @@ class ExampleHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   ExampleHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _ExampleHostApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _ExampleHostApiCodec();
 
   Future<String> getHostLanguage() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.getHostLanguage';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as String?)!;
+      return (__pigeon_replyList[0] as String?)!;
     }
   }
 
-  Future<int> add(int arg_a, int arg_b) async {
-    const String channelName =
+  Future<int> add(int a, int b) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.add';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_a, arg_b]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[a, b]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 
-  Future<bool> sendMessage(MessageData arg_message) async {
-    const String channelName =
+  Future<bool> sendMessage(MessageData message) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.sendMessage';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_message]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[message]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as bool?)!;
+      return (__pigeon_replyList[0] as bool?)!;
     }
   }
 }
 
 abstract class MessageFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   String flutterMethod(String? aString);
 
   static void setup(MessageFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_example_package.MessageFlutterApi.flutterMethod',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_example_package.MessageFlutterApi.flutterMethod was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/lib/ast.dart b/packages/pigeon/lib/ast.dart
index 820cdee8416..261ba62040d 100644
--- a/packages/pigeon/lib/ast.dart
+++ b/packages/pigeon/lib/ast.dart
@@ -28,7 +28,7 @@ class Method extends Node {
   Method({
     required this.name,
     required this.returnType,
-    required this.arguments,
+    required this.parameters,
     this.isAsynchronous = false,
     this.offset,
     this.objcSelector = '',
@@ -43,8 +43,8 @@ class Method extends Node {
   /// The data-type of the return value.
   TypeDeclaration returnType;
 
-  /// The arguments passed into the [Method].
-  List<NamedType> arguments;
+  /// The parameters passed into the [Method].
+  List<Parameter> parameters;
 
   /// Whether the receiver of this method is expected to return synchronously or not.
   bool isAsynchronous;
@@ -74,7 +74,7 @@ class Method extends Node {
         objcSelector.isEmpty ? '' : ' objcSelector:$objcSelector';
     final String swiftFunctionStr =
         swiftFunction.isEmpty ? '' : ' swiftFunction:$swiftFunction';
-    return '(Method name:$name returnType:$returnType arguments:$arguments isAsynchronous:$isAsynchronous$objcSelectorStr$swiftFunctionStr documentationComments:$documentationComments)';
+    return '(Method name:$name returnType:$returnType parameters:$parameters isAsynchronous:$isAsynchronous$objcSelectorStr$swiftFunctionStr documentationComments:$documentationComments)';
   }
 }
 
@@ -121,6 +121,8 @@ class TypeDeclaration {
   const TypeDeclaration({
     required this.baseName,
     required this.isNullable,
+    this.associatedEnum,
+    this.associatedClass,
     this.typeArguments = const <TypeDeclaration>[],
   });
 
@@ -128,20 +130,34 @@ class TypeDeclaration {
   const TypeDeclaration.voidDeclaration()
       : baseName = 'void',
         isNullable = false,
+        associatedEnum = null,
+        associatedClass = null,
         typeArguments = const <TypeDeclaration>[];
 
   /// The base name of the [TypeDeclaration] (ex 'Foo' to 'Foo<Bar>?').
   final String baseName;
 
-  /// Returns true if the declaration represents 'void'.
+  /// Whether the declaration represents 'void'.
   bool get isVoid => baseName == 'void';
 
-  /// The type arguments to the entity (ex 'Bar' to 'Foo<Bar>?').
+  /// Whether the type arguments to the entity (ex 'Bar' to 'Foo<Bar>?').
   final List<TypeDeclaration> typeArguments;
 
-  /// True if the type is nullable.
+  /// Whether the type is nullable.
   final bool isNullable;
 
+  /// Whether the [TypeDeclaration] has an [associatedEnum].
+  bool get isEnum => associatedEnum != null;
+
+  /// Associated [Enum], if any.
+  final Enum? associatedEnum;
+
+  /// Whether the [TypeDeclaration] has an [associatedClass].
+  bool get isClass => associatedClass != null;
+
+  /// Associated [Class], if any.
+  final Class? associatedClass;
+
   @override
   int get hashCode {
     // This has to be implemented because TypeDeclaration is used as a Key to a
@@ -163,47 +179,148 @@ class TypeDeclaration {
       return other is TypeDeclaration &&
           baseName == other.baseName &&
           isNullable == other.isNullable &&
-          _listEquals(typeArguments, other.typeArguments);
+          _listEquals(typeArguments, other.typeArguments) &&
+          isEnum == other.isEnum &&
+          isClass == other.isClass &&
+          associatedClass == other.associatedClass &&
+          associatedEnum == other.associatedEnum;
     }
   }
 
+  /// Returns duplicated `TypeDeclaration` with attached `associatedEnum` value.
+  TypeDeclaration copyWithEnum(Enum enumDefinition) {
+    return TypeDeclaration(
+      baseName: baseName,
+      isNullable: isNullable,
+      associatedEnum: enumDefinition,
+      typeArguments: typeArguments,
+    );
+  }
+
+  /// Returns duplicated `TypeDeclaration` with attached `associatedClass` value.
+  TypeDeclaration copyWithClass(Class classDefinition) {
+    return TypeDeclaration(
+      baseName: baseName,
+      isNullable: isNullable,
+      associatedClass: classDefinition,
+      typeArguments: typeArguments,
+    );
+  }
+
   @override
   String toString() {
     final String typeArgumentsStr =
         typeArguments.isEmpty ? '' : 'typeArguments:$typeArguments';
-    return '(TypeDeclaration baseName:$baseName isNullable:$isNullable$typeArgumentsStr)';
+    return '(TypeDeclaration baseName:$baseName isNullable:$isNullable$typeArgumentsStr isEnum:$isEnum isClass:$isClass)';
   }
 }
 
 /// Represents a named entity that has a type.
+@immutable
 class NamedType extends Node {
   /// Parametric constructor for [NamedType].
   NamedType({
     required this.name,
     required this.type,
     this.offset,
+    this.defaultValue,
     this.documentationComments = const <String>[],
   });
 
   /// The name of the entity.
-  String name;
+  final String name;
 
   /// The type.
-  TypeDeclaration type;
+  final TypeDeclaration type;
 
   /// The offset in the source file where the [NamedType] appears.
-  int? offset;
+  final int? offset;
+
+  /// Stringified version of the default value of types that have default values.
+  final String? defaultValue;
 
   /// List of documentation comments, separated by line.
   ///
   /// Lines should not include the comment marker itself, but should include any
   /// leading whitespace, so that any indentation in the original comment is preserved.
   /// For example: [" List of documentation comments, separated by line.", ...]
-  List<String> documentationComments;
+  final List<String> documentationComments;
+
+  /// Returns a copy of [NamedType] instance with new attached [TypeDeclaration].
+  NamedType copyWithType(TypeDeclaration type) {
+    return NamedType(
+      name: name,
+      type: type,
+      offset: offset,
+      defaultValue: defaultValue,
+      documentationComments: documentationComments,
+    );
+  }
+
+  @override
+  String toString() {
+    return '(NamedType name:$name type:$type defaultValue:$defaultValue documentationComments:$documentationComments)';
+  }
+}
+
+/// Represents a [Method]'s parameter that has a type and a name.
+@immutable
+class Parameter extends NamedType {
+  /// Parametric constructor for [Parameter].
+  Parameter({
+    required super.name,
+    required super.type,
+    super.offset,
+    super.defaultValue,
+    bool? isNamed,
+    bool? isOptional,
+    bool? isPositional,
+    bool? isRequired,
+    super.documentationComments,
+  })  : isNamed = isNamed ?? true,
+        isOptional = isOptional ?? false,
+        isPositional = isPositional ?? true,
+        isRequired = isRequired ?? true;
+
+  /// Whether this parameter is a named parameter.
+  ///
+  /// Defaults to `true`.
+  final bool isNamed;
+
+  /// Whether this parameter is an optional parameter.
+  ///
+  /// Defaults to `false`.
+  final bool isOptional;
+
+  /// Whether this parameter is a positional parameter.
+  ///
+  /// Defaults to `true`.
+  final bool isPositional;
+
+  /// Whether this parameter is a required parameter.
+  ///
+  /// Defaults to `true`.
+  final bool isRequired;
+
+  /// Returns a copy of [Parameter] instance with new attached [TypeDeclaration].
+  @override
+  Parameter copyWithType(TypeDeclaration type) {
+    return Parameter(
+      name: name,
+      type: type,
+      offset: offset,
+      defaultValue: defaultValue,
+      isNamed: isNamed,
+      isOptional: isOptional,
+      isPositional: isPositional,
+      isRequired: isRequired,
+      documentationComments: documentationComments,
+    );
+  }
 
   @override
   String toString() {
-    return '(NamedType name:$name type:$type documentationComments:$documentationComments)';
+    return '(Parameter name:$name type:$type isNamed:$isNamed isOptional:$isOptional isPositional:$isPositional isRequired:$isRequired documentationComments:$documentationComments)';
   }
 }
 
diff --git a/packages/pigeon/lib/ast_generator.dart b/packages/pigeon/lib/ast_generator.dart
index 4b6ecaade6e..2dff0bc4f32 100644
--- a/packages/pigeon/lib/ast_generator.dart
+++ b/packages/pigeon/lib/ast_generator.dart
@@ -5,7 +5,7 @@
 import 'ast.dart';
 import 'generator_tools.dart';
 
-/// Writes the AST represention of [root] to [sink].
+/// Writes the AST representation of [root] to [sink].
 void generateAst(Root root, StringSink sink) {
   final Indent indent = Indent(sink);
   final String output = root.toString();
diff --git a/packages/pigeon/lib/cpp_generator.dart b/packages/pigeon/lib/cpp_generator.dart
index fb52a13aa83..41c8226bb80 100644
--- a/packages/pigeon/lib/cpp_generator.dart
+++ b/packages/pigeon/lib/cpp_generator.dart
@@ -196,6 +196,7 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     final bool hasFlutterApi = root.apis.any((Api api) =>
         api.methods.isNotEmpty && api.location == ApiLocation.flutter);
 
+    _writeFlutterError(indent);
     if (hasHostApi) {
       _writeErrorOr(indent, friends: root.apis.map((Api api) => api.name));
     }
@@ -209,7 +210,7 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     // When generating for a Pigeon unit test, add a test fixture friend class to
@@ -227,31 +228,31 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     ];
 
     addDocumentationComments(
-        indent, klass.documentationComments, _docCommentSpec,
+        indent, classDefinition.documentationComments, _docCommentSpec,
         generatorComments: generatedMessages);
 
     final Iterable<NamedType> orderedFields =
-        getFieldsInSerializationOrder(klass);
+        getFieldsInSerializationOrder(classDefinition);
 
-    indent.write('class ${klass.name} ');
+    indent.write('class ${classDefinition.name} ');
     indent.addScoped('{', '};', () {
       _writeAccessBlock(indent, _ClassAccess.public, () {
         final Iterable<NamedType> requiredFields =
             orderedFields.where((NamedType type) => !type.type.isNullable);
         // Minimal constructor, if needed.
         if (requiredFields.length != orderedFields.length) {
-          _writeClassConstructor(root, indent, klass, requiredFields,
+          _writeClassConstructor(root, indent, classDefinition, requiredFields,
               'Constructs an object setting all non-nullable fields.');
         }
         // All-field constructor.
-        _writeClassConstructor(root, indent, klass, orderedFields,
+        _writeClassConstructor(root, indent, classDefinition, orderedFields,
             'Constructs an object setting all fields.');
 
         for (final NamedType field in orderedFields) {
           addDocumentationComments(
               indent, field.documentationComments, _docCommentSpec);
-          final HostDatatype baseDatatype = getFieldHostDatatype(
-              field, root.classes, root.enums, _baseCppTypeForBuiltinDartType);
+          final HostDatatype baseDatatype =
+              getFieldHostDatatype(field, _baseCppTypeForBuiltinDartType);
           // Declare a getter and setter.
           _writeFunctionDeclaration(indent, _makeGetterName(field),
               returnType: _getterReturnType(baseDatatype), isConst: true);
@@ -278,15 +279,15 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
 
       _writeAccessBlock(indent, _ClassAccess.private, () {
         _writeFunctionDeclaration(indent, 'FromEncodableList',
-            returnType: klass.name,
+            returnType: classDefinition.name,
             parameters: <String>['const flutter::EncodableList& list'],
             isStatic: true);
         _writeFunctionDeclaration(indent, 'ToEncodableList',
             returnType: 'flutter::EncodableList', isConst: true);
         for (final Class friend in root.classes) {
-          if (friend != klass &&
-              friend.fields.any(
-                  (NamedType element) => element.type.baseName == klass.name)) {
+          if (friend != classDefinition &&
+              friend.fields.any((NamedType element) =>
+                  element.type.baseName == classDefinition.name)) {
             indent.writeln('friend class ${friend.name};');
           }
         }
@@ -301,8 +302,8 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
         }
 
         for (final NamedType field in orderedFields) {
-          final HostDatatype hostDatatype = getFieldHostDatatype(
-              field, root.classes, root.enums, _baseCppTypeForBuiltinDartType);
+          final HostDatatype hostDatatype =
+              getFieldHostDatatype(field, _baseCppTypeForBuiltinDartType);
           indent.writeln(
               '${_valueType(hostDatatype)} ${_makeInstanceVariableName(field)};');
         }
@@ -336,18 +337,19 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
         _writeFunctionDeclaration(indent, 'GetCodec',
             returnType: 'const flutter::StandardMessageCodec&', isStatic: true);
         for (final Method func in api.methods) {
-          final HostDatatype returnType = getHostDatatype(func.returnType,
-              root.classes, root.enums, _baseCppTypeForBuiltinDartType);
+          final HostDatatype returnType =
+              getHostDatatype(func.returnType, _baseCppTypeForBuiltinDartType);
           addDocumentationComments(
               indent, func.documentationComments, _docCommentSpec);
 
-          final Iterable<String> argTypes = func.arguments.map((NamedType arg) {
-            final HostDatatype hostType = getFieldHostDatatype(
-                arg, root.classes, root.enums, _baseCppTypeForBuiltinDartType);
+          final Iterable<String> argTypes =
+              func.parameters.map((NamedType arg) {
+            final HostDatatype hostType =
+                getFieldHostDatatype(arg, _baseCppTypeForBuiltinDartType);
             return _flutterApiArgumentType(hostType);
           });
           final Iterable<String> argNames =
-              indexMap(func.arguments, _getArgumentName);
+              indexMap(func.parameters, _getArgumentName);
           final List<String> parameters = <String>[
             ...map2(argTypes, argNames, (String x, String y) => '$x $y'),
             ..._flutterApiCallbackParameters(returnType),
@@ -394,20 +396,20 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
         _writeFunctionDeclaration(indent, '~${api.name}',
             isVirtual: true, inlineNoop: true);
         for (final Method method in api.methods) {
-          final HostDatatype returnType = getHostDatatype(method.returnType,
-              root.classes, root.enums, _baseCppTypeForBuiltinDartType);
+          final HostDatatype returnType = getHostDatatype(
+              method.returnType, _baseCppTypeForBuiltinDartType);
           final String returnTypeName = _hostApiReturnType(returnType);
 
           final List<String> parameters = <String>[];
-          if (method.arguments.isNotEmpty) {
+          if (method.parameters.isNotEmpty) {
             final Iterable<String> argTypes =
-                method.arguments.map((NamedType arg) {
-              final HostDatatype hostType = getFieldHostDatatype(arg,
-                  root.classes, root.enums, _baseCppTypeForBuiltinDartType);
+                method.parameters.map((NamedType arg) {
+              final HostDatatype hostType =
+                  getFieldHostDatatype(arg, _baseCppTypeForBuiltinDartType);
               return _hostApiArgumentType(hostType);
             });
             final Iterable<String> argNames =
-                method.arguments.map((NamedType e) => _makeVariableName(e));
+                method.parameters.map((NamedType e) => _makeVariableName(e));
             parameters.addAll(
                 map2(argTypes, argNames, (String argType, String argName) {
               return '$argType $argName';
@@ -457,15 +459,15 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     }, nestCount: 0);
   }
 
-  void _writeClassConstructor(Root root, Indent indent, Class klass,
+  void _writeClassConstructor(Root root, Indent indent, Class classDefinition,
       Iterable<NamedType> params, String docComment) {
     final List<String> paramStrings = params.map((NamedType param) {
-      final HostDatatype hostDatatype = getFieldHostDatatype(
-          param, root.classes, root.enums, _baseCppTypeForBuiltinDartType);
+      final HostDatatype hostDatatype =
+          getFieldHostDatatype(param, _baseCppTypeForBuiltinDartType);
       return '${_hostApiArgumentType(hostDatatype)} ${_makeVariableName(param)}';
     }).toList();
     indent.writeln('$_commentPrefix $docComment');
-    _writeFunctionDeclaration(indent, klass.name,
+    _writeFunctionDeclaration(indent, classDefinition.name,
         isConstructor: true, parameters: paramStrings);
     indent.newln();
   }
@@ -509,11 +511,7 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     indent.newln();
   }
 
-  void _writeErrorOr(Indent indent,
-      {Iterable<String> friends = const <String>[]}) {
-    final String friendLines = friends
-        .map((String className) => '\tfriend class $className;')
-        .join('\n');
+  void _writeFlutterError(Indent indent) {
     indent.format('''
 
 class FlutterError {
@@ -533,7 +531,15 @@ class FlutterError {
 \tstd::string code_;
 \tstd::string message_;
 \tflutter::EncodableValue details_;
-};
+};''');
+  }
+
+  void _writeErrorOr(Indent indent,
+      {Iterable<String> friends = const <String>[]}) {
+    final String friendLines = friends
+        .map((String className) => '\tfriend class $className;')
+        .join('\n');
+    indent.format('''
 
 template<class T> class ErrorOr {
  public:
@@ -664,31 +670,27 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final Set<String> customClassNames =
-        root.classes.map((Class x) => x.name).toSet();
-    final Set<String> customEnumNames =
-        root.enums.map((Enum x) => x.name).toSet();
-
-    indent.writeln('$_commentPrefix ${klass.name}');
+    indent.writeln('$_commentPrefix ${classDefinition.name}');
     indent.newln();
 
     final Iterable<NamedType> orderedFields =
-        getFieldsInSerializationOrder(klass);
+        getFieldsInSerializationOrder(classDefinition);
     final Iterable<NamedType> requiredFields =
         orderedFields.where((NamedType type) => !type.type.isNullable);
     // Minimal constructor, if needed.
     if (requiredFields.length != orderedFields.length) {
-      _writeClassConstructor(root, indent, klass, requiredFields);
+      _writeClassConstructor(root, indent, classDefinition, requiredFields);
     }
     // All-field constructor.
-    _writeClassConstructor(root, indent, klass, orderedFields);
+    _writeClassConstructor(root, indent, classDefinition, orderedFields);
 
     // Getters and setters.
     for (final NamedType field in orderedFields) {
-      _writeCppSourceClassField(generatorOptions, root, indent, klass, field);
+      _writeCppSourceClassField(
+          generatorOptions, root, indent, classDefinition, field);
     }
 
     // Serialization.
@@ -696,9 +698,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
       generatorOptions,
       root,
       indent,
-      klass,
-      customClassNames,
-      customEnumNames,
+      classDefinition,
       dartPackageName: dartPackageName,
     );
 
@@ -707,9 +707,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
       generatorOptions,
       root,
       indent,
-      klass,
-      customClassNames,
-      customEnumNames,
+      classDefinition,
       dartPackageName: dartPackageName,
     );
   }
@@ -719,20 +717,19 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     _writeFunctionDefinition(indent, 'ToEncodableList',
-        scope: klass.name,
+        scope: classDefinition.name,
         returnType: 'EncodableList',
         isConst: true, body: () {
       indent.writeln('EncodableList list;');
-      indent.writeln('list.reserve(${klass.fields.length});');
-      for (final NamedType field in getFieldsInSerializationOrder(klass)) {
-        final HostDatatype hostDatatype = getFieldHostDatatype(field,
-            root.classes, root.enums, _shortBaseCppTypeForBuiltinDartType);
+      indent.writeln('list.reserve(${classDefinition.fields.length});');
+      for (final NamedType field
+          in getFieldsInSerializationOrder(classDefinition)) {
+        final HostDatatype hostDatatype =
+            getFieldHostDatatype(field, _shortBaseCppTypeForBuiltinDartType);
         final String encodableValue = _wrappedHostApiArgumentExpression(
             root, _makeInstanceVariableName(field), field.type, hostDatatype,
             preSerializeClasses: true);
@@ -747,23 +744,21 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     // Returns the expression to convert the given EncodableValue to a field
     // value.
     String getValueExpression(NamedType field, String encodable) {
-      if (customEnumNames.contains(field.type.baseName)) {
+      if (field.type.isEnum) {
         return '(${field.type.baseName})(std::get<int32_t>($encodable))';
       } else if (field.type.baseName == 'int') {
         return '$encodable.LongValue()';
       } else if (field.type.baseName == 'Object') {
         return encodable;
       } else {
-        final HostDatatype hostDatatype = getFieldHostDatatype(field,
-            root.classes, root.enums, _shortBaseCppTypeForBuiltinDartType);
+        final HostDatatype hostDatatype =
+            getFieldHostDatatype(field, _shortBaseCppTypeForBuiltinDartType);
         if (!hostDatatype.isBuiltin &&
             root.classes
                 .map((Class x) => x.name)
@@ -776,12 +771,12 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     }
 
     _writeFunctionDefinition(indent, 'FromEncodableList',
-        scope: klass.name,
-        returnType: klass.name,
+        scope: classDefinition.name,
+        returnType: classDefinition.name,
         parameters: <String>['const EncodableList& list'], body: () {
       const String instanceVariable = 'decoded';
       final Iterable<_IndexedField> indexedFields = indexMap(
-          getFieldsInSerializationOrder(klass),
+          getFieldsInSerializationOrder(classDefinition),
           (int index, NamedType field) => _IndexedField(index, field));
       final Iterable<_IndexedField> nullableFields = indexedFields
           .where((_IndexedField field) => field.field.type.isNullable);
@@ -796,7 +791,8 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
       if (constructorArgs.isNotEmpty) {
         constructorArgs = '(\n\t$constructorArgs)';
       }
-      indent.format('${klass.name} $instanceVariable$constructorArgs;');
+      indent
+          .format('${classDefinition.name} $instanceVariable$constructorArgs;');
 
       // Add the nullable fields via setters, since converting the encodable
       // values to the pointer types that the convenience constructor uses for
@@ -850,15 +846,15 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
           'return flutter::StandardMessageCodec::GetInstance(&$codeSerializerName::GetInstance());');
     });
     for (final Method func in api.methods) {
-      final HostDatatype returnType = getHostDatatype(func.returnType,
-          root.classes, root.enums, _shortBaseCppTypeForBuiltinDartType);
+      final HostDatatype returnType =
+          getHostDatatype(func.returnType, _shortBaseCppTypeForBuiltinDartType);
 
       // Determine the input parameter list, saved in a structured form for later
       // use as platform channel call arguments.
       final Iterable<_HostNamedType> hostParameters =
-          indexMap(func.arguments, (int i, NamedType arg) {
-        final HostDatatype hostType = getFieldHostDatatype(
-            arg, root.classes, root.enums, _shortBaseCppTypeForBuiltinDartType);
+          indexMap(func.parameters, (int i, NamedType arg) {
+        final HostDatatype hostType =
+            getFieldHostDatatype(arg, _shortBaseCppTypeForBuiltinDartType);
         return _HostNamedType(_getSafeArgumentName(i, arg), hostType, arg.type);
       });
       final List<String> parameters = <String>[
@@ -880,7 +876,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
         // Convert arguments to EncodableValue versions.
         const String argumentListVariableName = 'encoded_api_arguments';
         indent.write('EncodableValue $argumentListVariableName = ');
-        if (func.arguments.isEmpty) {
+        if (func.parameters.isEmpty) {
           indent.addln('EncodableValue();');
         } else {
           indent.addScoped('EncodableValue(EncodableList{', '});', () {
@@ -981,15 +977,13 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
             indent.addScoped('{', '});', () {
               indent.writeScoped('try {', '}', () {
                 final List<String> methodArgument = <String>[];
-                if (method.arguments.isNotEmpty) {
+                if (method.parameters.isNotEmpty) {
                   indent.writeln(
                       'const auto& args = std::get<EncodableList>(message);');
 
-                  enumerate(method.arguments, (int index, NamedType arg) {
+                  enumerate(method.parameters, (int index, NamedType arg) {
                     final HostDatatype hostType = getHostDatatype(
                         arg.type,
-                        root.classes,
-                        root.enums,
                         (TypeDeclaration x) =>
                             _shortBaseCppTypeForBuiltinDartType(x));
                     final String argName = _getSafeArgumentName(index, arg);
@@ -1015,7 +1009,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
                       apiType: ApiType.host,
                     );
                     final String unwrapEnum =
-                        isEnum(root, arg.type) && arg.type.isNullable
+                        arg.type.isEnum && arg.type.isNullable
                             ? ' ? &(*$argName) : nullptr'
                             : '';
                     methodArgument.add('$argName$unwrapEnum');
@@ -1023,10 +1017,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
                 }
 
                 final HostDatatype returnType = getHostDatatype(
-                    method.returnType,
-                    root.classes,
-                    root.enums,
-                    _shortBaseCppTypeForBuiltinDartType);
+                    method.returnType, _shortBaseCppTypeForBuiltinDartType);
                 final String returnTypeName = _hostApiReturnType(returnType);
                 if (method.isAsynchronous) {
                   methodArgument.add(
@@ -1150,15 +1141,13 @@ return EncodableValue(EncodableList{
     });
   }
 
-  void _writeClassConstructor(
-      Root root, Indent indent, Class klass, Iterable<NamedType> params) {
+  void _writeClassConstructor(Root root, Indent indent, Class classDefinition,
+      Iterable<NamedType> params) {
     final Iterable<_HostNamedType> hostParams = params.map((NamedType param) {
       return _HostNamedType(
         _makeVariableName(param),
         getFieldHostDatatype(
           param,
-          root.classes,
-          root.enums,
           _shortBaseCppTypeForBuiltinDartType,
         ),
         param.type,
@@ -1173,16 +1162,16 @@ return EncodableValue(EncodableList{
         .map((_HostNamedType param) =>
             '${param.name}_(${_fieldValueExpression(param.hostType, param.name)})')
         .toList();
-    _writeFunctionDefinition(indent, klass.name,
-        scope: klass.name,
+    _writeFunctionDefinition(indent, classDefinition.name,
+        scope: classDefinition.name,
         parameters: paramStrings,
         initializers: initializerStrings);
   }
 
   void _writeCppSourceClassField(CppOptions generatorOptions, Root root,
-      Indent indent, Class klass, NamedType field) {
-    final HostDatatype hostDatatype = getFieldHostDatatype(
-        field, root.classes, root.enums, _shortBaseCppTypeForBuiltinDartType);
+      Indent indent, Class classDefinition, NamedType field) {
+    final HostDatatype hostDatatype =
+        getFieldHostDatatype(field, _shortBaseCppTypeForBuiltinDartType);
     final String instanceVariableName = _makeInstanceVariableName(field);
     final String setterName = _makeSetterName(field);
     final String returnExpression = hostDatatype.isNullable
@@ -1196,7 +1185,7 @@ return EncodableValue(EncodableList{
       _writeFunctionDefinition(
         indent,
         setterName,
-        scope: klass.name,
+        scope: classDefinition.name,
         returnType: _voidType,
         parameters: <String>[
           '${_unownedArgumentType(type)} $setterArgumentName'
@@ -1211,7 +1200,7 @@ return EncodableValue(EncodableList{
     _writeFunctionDefinition(
       indent,
       _makeGetterName(field),
-      scope: klass.name,
+      scope: classDefinition.name,
       returnType: _getterReturnType(hostDatatype),
       isConst: true,
       body: () {
@@ -1247,7 +1236,7 @@ return EncodableValue(EncodableList{
 
     const String nullValue = 'EncodableValue()';
     String enumPrefix = '';
-    if (isEnum(root, returnType)) {
+    if (returnType.isEnum) {
       enumPrefix = '(int) ';
     }
     if (returnType.isVoid) {
@@ -1255,11 +1244,11 @@ return EncodableValue(EncodableList{
       errorCondition = 'output.has_value()';
       errorGetter = 'value';
     } else {
-      final HostDatatype hostType = getHostDatatype(returnType, root.classes,
-          root.enums, _shortBaseCppTypeForBuiltinDartType);
+      final HostDatatype hostType =
+          getHostDatatype(returnType, _shortBaseCppTypeForBuiltinDartType);
 
       const String extractedValue = 'std::move(output).TakeValue()';
-      final String wrapperType = hostType.isBuiltin || isEnum(root, returnType)
+      final String wrapperType = hostType.isBuiltin || returnType.isEnum
           ? 'EncodableValue'
           : 'CustomEncodableValue';
       if (returnType.isNullable) {
@@ -1818,8 +1807,8 @@ List<Error> validateCpp(CppOptions options, Root root) {
   final List<Error> result = <Error>[];
   for (final Api api in root.apis) {
     for (final Method method in api.methods) {
-      for (final NamedType arg in method.arguments) {
-        if (isEnum(root, arg.type)) {
+      for (final NamedType arg in method.parameters) {
+        if (arg.type.isEnum) {
           // TODO(gaaclarke): Add line number and filename.
           result.add(Error(
               message:
diff --git a/packages/pigeon/lib/dart_generator.dart b/packages/pigeon/lib/dart_generator.dart
index 672cab1c070..1f0b4dac38c 100644
--- a/packages/pigeon/lib/dart_generator.dart
+++ b/packages/pigeon/lib/dart_generator.dart
@@ -12,6 +12,15 @@ import 'generator_tools.dart';
 /// Documentation comment open symbol.
 const String _docCommentPrefix = '///';
 
+/// Prefix for all local variables in host API methods.
+///
+/// This lowers the chances of variable name collisions with
+/// user defined parameters.
+const String _varNamePrefix = '__pigeon_';
+
+/// Name of field used for host API codec.
+const String _pigeonChannelCodec = 'pigeonChannelCodec';
+
 /// Documentation comment spec.
 const DocumentCommentSpecification _docCommentSpec =
     DocumentCommentSpecification(_docCommentPrefix);
@@ -85,7 +94,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
     indent.writeln('// ${getGeneratedCodeWarning()}');
     indent.writeln('// $seeAlsoWarning');
     indent.writeln(
-      '// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import',
+      '// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers',
     );
     indent.newln();
   }
@@ -133,23 +142,19 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
     DartOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final Set<String> customClassNames =
-        root.classes.map((Class x) => x.name).toSet();
-    final Set<String> customEnumNames =
-        root.enums.map((Enum x) => x.name).toSet();
-
     indent.newln();
     addDocumentationComments(
-        indent, klass.documentationComments, _docCommentSpec);
+        indent, classDefinition.documentationComments, _docCommentSpec);
 
-    indent.write('class ${klass.name} ');
+    indent.write('class ${classDefinition.name} ');
     indent.addScoped('{', '}', () {
-      _writeConstructor(indent, klass);
+      _writeConstructor(indent, classDefinition);
       indent.newln();
-      for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+      for (final NamedType field
+          in getFieldsInSerializationOrder(classDefinition)) {
         addDocumentationComments(
             indent, field.documentationComments, _docCommentSpec);
 
@@ -161,9 +166,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
       indent.newln();
@@ -171,20 +174,24 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
     });
   }
 
-  void _writeConstructor(Indent indent, Class klass) {
-    indent.write(klass.name);
+  void _writeConstructor(Indent indent, Class classDefinition) {
+    indent.write(classDefinition.name);
     indent.addScoped('({', '});', () {
-      for (final NamedType field in getFieldsInSerializationOrder(klass)) {
-        final String required = field.type.isNullable ? '' : 'required ';
-        indent.writeln('${required}this.${field.name},');
+      for (final NamedType field
+          in getFieldsInSerializationOrder(classDefinition)) {
+        final String required =
+            !field.type.isNullable && field.defaultValue == null
+                ? 'required '
+                : '';
+        final String defaultValueString =
+            field.defaultValue == null ? '' : ' = ${field.defaultValue}';
+        indent.writeln('${required}this.${field.name}$defaultValueString,');
       }
     });
   }
@@ -194,9 +201,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
     DartOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     indent.write('Object encode() ');
@@ -205,13 +210,14 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
         'return <Object?>',
       );
       indent.addScoped('[', '];', () {
-        for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+        for (final NamedType field
+            in getFieldsInSerializationOrder(classDefinition)) {
           final String conditional = field.type.isNullable ? '?' : '';
-          if (customClassNames.contains(field.type.baseName)) {
+          if (field.type.isClass) {
             indent.writeln(
               '${field.name}$conditional.encode(),',
             );
-          } else if (customEnumNames.contains(field.type.baseName)) {
+          } else if (field.type.isEnum) {
             indent.writeln(
               '${field.name}$conditional.index,',
             );
@@ -228,9 +234,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
     DartOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     void writeValueDecode(NamedType field, int index) {
@@ -239,7 +243,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
       final String genericType = _makeGenericTypeArguments(field.type);
       final String castCall = _makeGenericCastCall(field.type);
       final String nullableTag = field.type.isNullable ? '?' : '';
-      if (customClassNames.contains(field.type.baseName)) {
+      if (field.type.isClass) {
         final String nonNullValue =
             '${field.type.baseName}.decode($resultAt! as List<Object?>)';
         if (field.type.isNullable) {
@@ -250,7 +254,7 @@ $resultAt != null
         } else {
           indent.add(nonNullValue);
         }
-      } else if (customEnumNames.contains(field.type.baseName)) {
+      } else if (field.type.isEnum) {
         final String nonNullValue =
             '${field.type.baseName}.values[$resultAt! as int]';
         if (field.type.isNullable) {
@@ -278,13 +282,13 @@ $resultAt != null
     }
 
     indent.write(
-      'static ${klass.name} decode(Object result) ',
+      'static ${classDefinition.name} decode(Object result) ',
     );
     indent.addScoped('{', '}', () {
       indent.writeln('result as List<Object?>;');
-      indent.write('return ${klass.name}');
+      indent.write('return ${classDefinition.name}');
       indent.addScoped('(', ');', () {
-        enumerate(getFieldsInSerializationOrder(klass),
+        enumerate(getFieldsInSerializationOrder(classDefinition),
             (int index, final NamedType field) {
           indent.write('${field.name}: ');
           writeValueDecode(field, index);
@@ -314,8 +318,6 @@ $resultAt != null
     required String dartPackageName,
   }) {
     assert(api.location == ApiLocation.flutter);
-    final List<String> customEnumNames =
-        root.enums.map((Enum x) => x.name).toList();
     String codecName = _standardMessageCodec;
     if (getCodecClasses(api, root).isNotEmpty) {
       codecName = _getCodecName(api);
@@ -331,8 +333,8 @@ $resultAt != null
         indent.writeln(
             'static TestDefaultBinaryMessengerBinding? get _testBinaryMessengerBinding => TestDefaultBinaryMessengerBinding.instance;');
       }
-      indent
-          .writeln('static const MessageCodec<Object?> codec = $codecName();');
+      indent.writeln(
+          'static const MessageCodec<Object?> $_pigeonChannelCodec = $codecName();');
       indent.newln();
       for (final Method func in api.methods) {
         addDocumentationComments(
@@ -342,10 +344,7 @@ $resultAt != null
         final String returnType = isAsync
             ? 'Future<${_addGenericTypesNullable(func.returnType)}>'
             : _addGenericTypesNullable(func.returnType);
-        final String argSignature = _getMethodArgumentsSignature(
-          func,
-          _getArgumentName,
-        );
+        final String argSignature = _getMethodParameterSignature(func);
         indent.writeln('$returnType ${func.name}($argSignature);');
         indent.newln();
       }
@@ -356,20 +355,20 @@ $resultAt != null
           indent.write('');
           indent.addScoped('{', '}', () {
             indent.writeln(
-              'final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(',
+              'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
             );
             final String channelName = channelNameFunc == null
                 ? makeChannelName(api, func, dartPackageName)
                 : channelNameFunc(func);
             indent.nest(2, () {
-              indent.writeln("'$channelName', codec,");
+              indent.writeln("'$channelName', $_pigeonChannelCodec,");
               indent.writeln(
                 'binaryMessenger: binaryMessenger);',
               );
             });
             final String messageHandlerSetterWithOpeningParentheses = isMockHandler
-                ? '_testBinaryMessengerBinding!.defaultBinaryMessenger.setMockDecodedMessageHandler<Object?>(channel, '
-                : 'channel.setMessageHandler(';
+                ? '_testBinaryMessengerBinding!.defaultBinaryMessenger.setMockDecodedMessageHandler<Object?>(${_varNamePrefix}channel, '
+                : '${_varNamePrefix}channel.setMessageHandler(';
             indent.write('if (api == null) ');
             indent.addScoped('{', '}', () {
               indent.writeln(
@@ -387,7 +386,7 @@ $resultAt != null
                 const String emptyReturnStatement =
                     'return wrapResponse(empty: true);';
                 String call;
-                if (func.arguments.isEmpty) {
+                if (func.parameters.isEmpty) {
                   call = 'api.${func.name}()';
                 } else {
                   indent.writeln('assert(message != null,');
@@ -397,7 +396,7 @@ $resultAt != null
                       'final List<Object?> $argsArray = (message as List<Object?>?)!;');
                   String argNameFunc(int index, NamedType type) =>
                       _getSafeArgumentName(index, type);
-                  enumerate(func.arguments, (int count, NamedType arg) {
+                  enumerate(func.parameters, (int count, NamedType arg) {
                     final String argType = _addGenericTypes(arg.type);
                     final String argName = argNameFunc(count, arg);
                     final String genericArgType =
@@ -405,7 +404,7 @@ $resultAt != null
                     final String castCall = _makeGenericCastCall(arg.type);
 
                     final String leftHandSide = 'final $argType? $argName';
-                    if (customEnumNames.contains(arg.type.baseName)) {
+                    if (arg.type.isEnum) {
                       indent.writeln(
                           '$leftHandSide = $argsArray[$count] == null ? null : $argType.values[$argsArray[$count]! as int];');
                     } else {
@@ -419,7 +418,7 @@ $resultAt != null
                     }
                   });
                   final Iterable<String> argNames =
-                      indexMap(func.arguments, (int index, NamedType field) {
+                      indexMap(func.parameters, (int index, NamedType field) {
                     final String name = _getSafeArgumentName(index, field);
                     return '$name${field.type.isNullable ? '' : '!'}';
                   });
@@ -443,9 +442,8 @@ $resultAt != null
                     const String returnExpression = 'output';
                     final String nullability =
                         func.returnType.isNullable ? '?' : '';
-                    final String valueExtraction = isEnum(root, func.returnType)
-                        ? '$nullability.index'
-                        : '';
+                    final String valueExtraction =
+                        func.returnType.isEnum ? '$nullability.index' : '';
                     final String returnStatement = isMockHandler
                         ? 'return <Object?>[$returnExpression$valueExtraction];'
                         : 'return wrapResponse(result: $returnExpression$valueExtraction);';
@@ -499,8 +497,6 @@ $resultAt != null
       codecName = _getCodecName(api);
       _writeCodec(indent, codecName, api, root);
     }
-    final List<String> customEnumNames =
-        root.enums.map((Enum x) => x.name).toList();
     indent.newln();
     bool first = true;
     addDocumentationComments(
@@ -512,12 +508,12 @@ $resultAt != null
 /// available for dependency injection.  If it is left null, the default
 /// BinaryMessenger will be used which routes to the host platform.
 ${api.name}({BinaryMessenger? binaryMessenger})
-\t\t: _binaryMessenger = binaryMessenger;
-final BinaryMessenger? _binaryMessenger;
+\t\t: ${_varNamePrefix}binaryMessenger = binaryMessenger;
+final BinaryMessenger? ${_varNamePrefix}binaryMessenger;
 ''');
 
-      indent
-          .writeln('static const MessageCodec<Object?> codec = $codecName();');
+      indent.writeln(
+          'static const MessageCodec<Object?> $_pigeonChannelCodec = $codecName();');
       indent.newln();
       for (final Method func in api.methods) {
         if (!first) {
@@ -529,39 +525,36 @@ final BinaryMessenger? _binaryMessenger;
             indent, func.documentationComments, _docCommentSpec);
         String argSignature = '';
         String sendArgument = 'null';
-        if (func.arguments.isNotEmpty) {
-          String argNameFunc(int index, NamedType type) =>
-              _getSafeArgumentName(index, type);
+        if (func.parameters.isNotEmpty) {
           final Iterable<String> argExpressions =
-              indexMap(func.arguments, (int index, NamedType type) {
-            final String name = argNameFunc(index, type);
-            if (root.enums
-                .map((Enum e) => e.name)
-                .contains(type.type.baseName)) {
+              indexMap(func.parameters, (int index, NamedType type) {
+            final String name = _getParameterName(index, type);
+            if (type.type.isEnum) {
               return '$name${type.type.isNullable ? '?' : ''}.index';
             } else {
               return name;
             }
           });
           sendArgument = '<Object?>[${argExpressions.join(', ')}]';
-          argSignature = _getMethodArgumentsSignature(func, argNameFunc);
+          argSignature = _getMethodParameterSignature(func);
         }
         indent.write(
           'Future<${_addGenericTypesNullable(func.returnType)}> ${func.name}($argSignature) async ',
         );
         indent.addScoped('{', '}', () {
           indent.writeln(
-              "const String channelName = '${makeChannelName(api, func, dartPackageName)}';");
+              "const String ${_varNamePrefix}channelName = '${makeChannelName(api, func, dartPackageName)}';");
           indent.writeScoped(
-              'final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(',
+              'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
               ');', () {
-            indent.writeln('channelName,');
-            indent.writeln('codec,');
-            indent.writeln('binaryMessenger: _binaryMessenger,');
+            indent.writeln('${_varNamePrefix}channelName,');
+            indent.writeln('$_pigeonChannelCodec,');
+            indent
+                .writeln('binaryMessenger: ${_varNamePrefix}binaryMessenger,');
           });
           final String returnType = _makeGenericTypeArguments(func.returnType);
           final String genericCastCall = _makeGenericCastCall(func.returnType);
-          const String accessor = 'replyList[0]';
+          const String accessor = '${_varNamePrefix}replyList[0]';
           // Avoid warnings from pointlessly casting to `Object?`.
           final String nullablyTypedAccessor =
               returnType == 'Object' ? accessor : '($accessor as $returnType?)';
@@ -569,7 +562,7 @@ final BinaryMessenger? _binaryMessenger;
               ? (genericCastCall.isEmpty ? '' : '?')
               : '!';
           String returnStatement = 'return';
-          if (customEnumNames.contains(returnType)) {
+          if (func.returnType.isEnum) {
             if (func.returnType.isNullable) {
               returnStatement =
                   '$returnStatement ($accessor as int?) == null ? null : $returnType.values[$accessor! as int]';
@@ -584,22 +577,22 @@ final BinaryMessenger? _binaryMessenger;
           returnStatement = '$returnStatement;';
 
           indent.format('''
-final List<Object?>? replyList =
-\t\tawait channel.send($sendArgument) as List<Object?>?;
-if (replyList == null) {
-\tthrow _createConnectionError(channelName);
-} else if (replyList.length > 1) {
+final List<Object?>? ${_varNamePrefix}replyList =
+\t\tawait ${_varNamePrefix}channel.send($sendArgument) as List<Object?>?;
+if (${_varNamePrefix}replyList == null) {
+\tthrow _createConnectionError(${_varNamePrefix}channelName);
+} else if (${_varNamePrefix}replyList.length > 1) {
 \tthrow PlatformException(
-\t\tcode: replyList[0]! as String,
-\t\tmessage: replyList[1] as String?,
-\t\tdetails: replyList[2],
+\t\tcode: ${_varNamePrefix}replyList[0]! as String,
+\t\tmessage: ${_varNamePrefix}replyList[1] as String?,
+\t\tdetails: ${_varNamePrefix}replyList[2],
 \t);''');
           // On iOS we can return nil from functions to accommodate error
           // handling.  Returning a nil value and not returning an error is an
           // exception.
           if (!func.returnType.isNullable && !func.returnType.isVoid) {
             indent.format('''
-} else if (replyList[0] == null) {
+} else if (${_varNamePrefix}replyList[0] == null) {
 \tthrow PlatformException(
 \t\tcode: 'null-error',
 \t\tmessage: 'Host platform returned null value for non-null return value.',
@@ -678,7 +671,7 @@ if (replyList == null) {
     indent.writeln('// ${getGeneratedCodeWarning()}');
     indent.writeln('// $seeAlsoWarning');
     indent.writeln(
-      '// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, unnecessary_import',
+      '// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, unnecessary_import, no_leading_underscores_for_local_identifiers',
     );
     indent.writeln('// ignore_for_file: avoid_relative_lib_imports');
   }
@@ -825,23 +818,67 @@ String _makeGenericCastCall(TypeDeclaration type) {
 String _getSafeArgumentName(int count, NamedType field) =>
     field.name.isEmpty ? 'arg$count' : 'arg_${field.name}';
 
-/// Generates an argument name if one isn't defined.
-String _getArgumentName(int count, NamedType field) =>
+/// Generates a parameter name if one isn't defined.
+String _getParameterName(int count, NamedType field) =>
     field.name.isEmpty ? 'arg$count' : field.name;
 
-/// Generates the arguments code for [func]
-/// Example: (func, getArgumentName) -> 'String? foo, int bar'
-String _getMethodArgumentsSignature(
-  Method func,
-  String Function(int index, NamedType arg) getArgumentName,
-) {
-  return func.arguments.isEmpty
-      ? ''
-      : indexMap(func.arguments, (int index, NamedType arg) {
-          final String type = _addGenericTypesNullable(arg.type);
-          final String argName = getArgumentName(index, arg);
-          return '$type $argName';
-        }).join(', ');
+/// Generates the parameters code for [func]
+/// Example: (func, _getParameterName) -> 'String? foo, int bar'
+String _getMethodParameterSignature(Method func) {
+  String signature = '';
+  if (func.parameters.isEmpty) {
+    return signature;
+  }
+
+  final List<Parameter> requiredPositionalParams = func.parameters
+      .where((Parameter p) => p.isPositional && !p.isOptional)
+      .toList();
+  final List<Parameter> optionalPositionalParams = func.parameters
+      .where((Parameter p) => p.isPositional && p.isOptional)
+      .toList();
+  final List<Parameter> namedParams =
+      func.parameters.where((Parameter p) => !p.isPositional).toList();
+
+  String getParameterString(Parameter p) {
+    final String required = p.isRequired && !p.isPositional ? 'required ' : '';
+
+    final String type = _addGenericTypesNullable(p.type);
+
+    final String defaultValue =
+        p.defaultValue == null ? '' : ' = ${p.defaultValue}';
+    return '$required$type ${p.name}$defaultValue';
+  }
+
+  final String baseParameterString = requiredPositionalParams
+      .map((Parameter p) => getParameterString(p))
+      .join(', ');
+  final String optionalParameterString = optionalPositionalParams
+      .map((Parameter p) => getParameterString(p))
+      .join(', ');
+  final String namedParameterString =
+      namedParams.map((Parameter p) => getParameterString(p)).join(', ');
+
+  // Parameter lists can end with either named or optional positional parameters, but not both.
+  if (requiredPositionalParams.isNotEmpty) {
+    signature = baseParameterString;
+  }
+  final String trailingComma =
+      optionalPositionalParams.isNotEmpty || namedParams.isNotEmpty ? ',' : '';
+  final String baseParams =
+      signature.isNotEmpty ? '$signature$trailingComma ' : '';
+  if (optionalPositionalParams.isNotEmpty) {
+    final String trailingComma =
+        requiredPositionalParams.length + optionalPositionalParams.length > 2
+            ? ','
+            : '';
+    return '$baseParams[$optionalParameterString$trailingComma]';
+  }
+  if (namedParams.isNotEmpty) {
+    final String trailingComma =
+        requiredPositionalParams.length + namedParams.length > 2 ? ',' : '';
+    return '$baseParams{$namedParameterString$trailingComma}';
+  }
+  return signature;
 }
 
 /// Converts a [List] of [TypeDeclaration]s to a comma separated [String] to be
diff --git a/packages/pigeon/lib/generator.dart b/packages/pigeon/lib/generator.dart
index cf9dc78cdb2..1bd08307874 100644
--- a/packages/pigeon/lib/generator.dart
+++ b/packages/pigeon/lib/generator.dart
@@ -176,12 +176,12 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     Indent indent, {
     required String dartPackageName,
   }) {
-    for (final Class klass in root.classes) {
+    for (final Class classDefinition in root.classes) {
       writeDataClass(
         generatorOptions,
         root,
         indent,
-        klass,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
     }
@@ -192,7 +192,7 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     T generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   });
 
@@ -201,9 +201,7 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     T generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {}
 
@@ -212,9 +210,7 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     T generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {}
 
diff --git a/packages/pigeon/lib/generator_tools.dart b/packages/pigeon/lib/generator_tools.dart
index cd51c71affe..050bbacb974 100644
--- a/packages/pigeon/lib/generator_tools.dart
+++ b/packages/pigeon/lib/generator_tools.dart
@@ -13,7 +13,7 @@ import 'ast.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '13.1.2';
+const String pigeonVersion = '14.0.0';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {
@@ -169,6 +169,8 @@ String makeChannelName(Api api, Method func, String dartPackageName) {
   return 'dev.flutter.pigeon.$dartPackageName.${api.name}.${func.name}';
 }
 
+// TODO(tarrinneal): Determine whether HostDataType is needed.
+
 /// Represents the mapping of a Dart datatype to a Host datatype.
 class HostDatatype {
   /// Parametric constructor for HostDatatype.
@@ -199,10 +201,10 @@ class HostDatatype {
 /// datatype for the Dart datatype for builtin types.
 ///
 /// [customResolver] can modify the datatype of custom types.
-HostDatatype getFieldHostDatatype(NamedType field, List<Class> classes,
-    List<Enum> enums, String? Function(TypeDeclaration) builtinResolver,
+HostDatatype getFieldHostDatatype(
+    NamedType field, String? Function(TypeDeclaration) builtinResolver,
     {String Function(String)? customResolver}) {
-  return _getHostDatatype(field.type, classes, enums, builtinResolver,
+  return _getHostDatatype(field.type, builtinResolver,
       customResolver: customResolver, fieldName: field.name);
 }
 
@@ -213,19 +215,19 @@ HostDatatype getFieldHostDatatype(NamedType field, List<Class> classes,
 /// datatype for the Dart datatype for builtin types.
 ///
 /// [customResolver] can modify the datatype of custom types.
-HostDatatype getHostDatatype(TypeDeclaration type, List<Class> classes,
-    List<Enum> enums, String? Function(TypeDeclaration) builtinResolver,
+HostDatatype getHostDatatype(
+    TypeDeclaration type, String? Function(TypeDeclaration) builtinResolver,
     {String Function(String)? customResolver}) {
-  return _getHostDatatype(type, classes, enums, builtinResolver,
+  return _getHostDatatype(type, builtinResolver,
       customResolver: customResolver);
 }
 
-HostDatatype _getHostDatatype(TypeDeclaration type, List<Class> classes,
-    List<Enum> enums, String? Function(TypeDeclaration) builtinResolver,
+HostDatatype _getHostDatatype(
+    TypeDeclaration type, String? Function(TypeDeclaration) builtinResolver,
     {String Function(String)? customResolver, String? fieldName}) {
   final String? datatype = builtinResolver(type);
   if (datatype == null) {
-    if (classes.map((Class x) => x.name).contains(type.baseName)) {
+    if (type.isClass) {
       final String customName = customResolver != null
           ? customResolver(type.baseName)
           : type.baseName;
@@ -235,7 +237,7 @@ HostDatatype _getHostDatatype(TypeDeclaration type, List<Class> classes,
         isNullable: type.isNullable,
         isEnum: false,
       );
-    } else if (enums.map((Enum x) => x.name).contains(type.baseName)) {
+    } else if (type.isEnum) {
       final String customName = customResolver != null
           ? customResolver(type.baseName)
           : type.baseName;
@@ -412,7 +414,7 @@ Map<TypeDeclaration, List<int>> getReferencedTypes(
   final _Bag<TypeDeclaration, int> references = _Bag<TypeDeclaration, int>();
   for (final Api api in apis) {
     for (final Method method in api.methods) {
-      for (final NamedType field in method.arguments) {
+      for (final NamedType field in method.parameters) {
         references.addMany(_getTypeArguments(field.type), field.offset);
       }
       references.addMany(_getTypeArguments(method.returnType), method.offset);
@@ -478,10 +480,6 @@ Iterable<EnumeratedClass> getCodecClasses(Api api, Root root) sync* {
   }
 }
 
-/// Returns true if the [TypeDeclaration] represents an enum.
-bool isEnum(Root root, TypeDeclaration type) =>
-    root.enums.map((Enum e) => e.name).contains(type.baseName);
-
 /// Describes how to format a document comment.
 class DocumentCommentSpecification {
   /// Constructor for [DocumentationCommentSpecification]
@@ -542,9 +540,9 @@ void addDocumentationComments(
 }
 
 /// Returns an ordered list of fields to provide consistent serialization order.
-Iterable<NamedType> getFieldsInSerializationOrder(Class klass) {
+Iterable<NamedType> getFieldsInSerializationOrder(Class classDefinition) {
   // This returns the fields in the order they are declared in the pigeon file.
-  return klass.fields;
+  return classDefinition.fields;
 }
 
 /// Crawls up the path of [dartFilePath] until it finds a pubspec.yaml in a
diff --git a/packages/pigeon/lib/java_generator.dart b/packages/pigeon/lib/java_generator.dart
index ca1e3b5bd1a..16e806a170b 100644
--- a/packages/pigeon/lib/java_generator.dart
+++ b/packages/pigeon/lib/java_generator.dart
@@ -196,55 +196,47 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     JavaOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final Set<String> customClassNames =
-        root.classes.map((Class x) => x.name).toSet();
-    final Set<String> customEnumNames =
-        root.enums.map((Enum x) => x.name).toSet();
-
     const List<String> generatedMessages = <String>[
       ' Generated class from Pigeon that represents data sent in messages.'
     ];
     indent.newln();
     addDocumentationComments(
-        indent, klass.documentationComments, _docCommentSpec,
+        indent, classDefinition.documentationComments, _docCommentSpec,
         generatorComments: generatedMessages);
 
-    indent.write('public static final class ${klass.name} ');
+    indent.write('public static final class ${classDefinition.name} ');
     indent.addScoped('{', '}', () {
-      for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+      for (final NamedType field
+          in getFieldsInSerializationOrder(classDefinition)) {
         _writeClassField(generatorOptions, root, indent, field);
         indent.newln();
       }
 
-      if (getFieldsInSerializationOrder(klass)
+      if (getFieldsInSerializationOrder(classDefinition)
           .map((NamedType e) => !e.type.isNullable)
           .any((bool e) => e)) {
         indent.writeln(
             '$_docCommentPrefix Constructor is non-public to enforce null safety; use Builder.$_docCommentSuffix');
-        indent.writeln('${klass.name}() {}');
+        indent.writeln('${classDefinition.name}() {}');
         indent.newln();
       }
 
-      _writeClassBuilder(generatorOptions, root, indent, klass);
+      _writeClassBuilder(generatorOptions, root, indent, classDefinition);
       writeClassEncode(
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
       writeClassDecode(
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
     });
@@ -252,8 +244,8 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
 
   void _writeClassField(
       JavaOptions generatorOptions, Root root, Indent indent, NamedType field) {
-    final HostDatatype hostDatatype = getFieldHostDatatype(field, root.classes,
-        root.enums, (TypeDeclaration x) => _javaTypeForBuiltinDartType(x));
+    final HostDatatype hostDatatype = getFieldHostDatatype(
+        field, (TypeDeclaration x) => _javaTypeForBuiltinDartType(x));
     final String nullability = field.type.isNullable ? '@Nullable' : '@NonNull';
     addDocumentationComments(
         indent, field.documentationComments, _docCommentSpec);
@@ -284,16 +276,14 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     JavaOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
+    Class classDefinition,
   ) {
     indent.write('public static final class Builder ');
     indent.addScoped('{', '}', () {
-      for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+      for (final NamedType field
+          in getFieldsInSerializationOrder(classDefinition)) {
         final HostDatatype hostDatatype = getFieldHostDatatype(
-            field,
-            root.classes,
-            root.enums,
-            (TypeDeclaration x) => _javaTypeForBuiltinDartType(x));
+            field, (TypeDeclaration x) => _javaTypeForBuiltinDartType(x));
         final String nullability =
             field.type.isNullable ? '@Nullable' : '@NonNull';
         indent.newln();
@@ -308,11 +298,13 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
         });
       }
       indent.newln();
-      indent.write('public @NonNull ${klass.name} build() ');
+      indent.write('public @NonNull ${classDefinition.name} build() ');
       indent.addScoped('{', '}', () {
         const String returnVal = 'pigeonReturn';
-        indent.writeln('${klass.name} $returnVal = new ${klass.name}();');
-        for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+        indent.writeln(
+            '${classDefinition.name} $returnVal = new ${classDefinition.name}();');
+        for (final NamedType field
+            in getFieldsInSerializationOrder(classDefinition)) {
           indent.writeln('$returnVal.${_makeSetter(field)}(${field.name});');
         }
         indent.writeln('return $returnVal;');
@@ -325,9 +317,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     JavaOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     indent.newln();
@@ -335,20 +325,14 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     indent.write('ArrayList<Object> toList() ');
     indent.addScoped('{', '}', () {
       indent.writeln(
-          'ArrayList<Object> toListResult = new ArrayList<Object>(${klass.fields.length});');
-      for (final NamedType field in getFieldsInSerializationOrder(klass)) {
-        final HostDatatype hostDatatype = getFieldHostDatatype(
-            field,
-            root.classes,
-            root.enums,
-            (TypeDeclaration x) => _javaTypeForBuiltinDartType(x));
+          'ArrayList<Object> toListResult = new ArrayList<Object>(${classDefinition.fields.length});');
+      for (final NamedType field
+          in getFieldsInSerializationOrder(classDefinition)) {
         String toWriteValue = '';
         final String fieldName = field.name;
-        if (!hostDatatype.isBuiltin &&
-            customClassNames.contains(field.type.baseName)) {
+        if (field.type.isClass) {
           toWriteValue = '($fieldName == null) ? null : $fieldName.toList()';
-        } else if (!hostDatatype.isBuiltin &&
-            customEnumNames.contains(field.type.baseName)) {
+        } else if (field.type.isEnum) {
           toWriteValue = '$fieldName == null ? null : $fieldName.index';
         } else {
           toWriteValue = field.name;
@@ -364,28 +348,27 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     JavaOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     indent.newln();
     indent.write(
-        'static @NonNull ${klass.name} fromList(@NonNull ArrayList<Object> list) ');
+        'static @NonNull ${classDefinition.name} fromList(@NonNull ArrayList<Object> list) ');
     indent.addScoped('{', '}', () {
       const String result = 'pigeonResult';
-      indent.writeln('${klass.name} $result = new ${klass.name}();');
-      enumerate(getFieldsInSerializationOrder(klass),
+      indent.writeln(
+          '${classDefinition.name} $result = new ${classDefinition.name}();');
+      enumerate(getFieldsInSerializationOrder(classDefinition),
           (int index, final NamedType field) {
         final String fieldVariable = field.name;
         final String setter = _makeSetter(field);
         indent.writeln('Object $fieldVariable = list.get($index);');
-        if (customEnumNames.contains(field.type.baseName)) {
+        if (field.type.isEnum) {
           indent.writeln(
               '$result.$setter(${_intToEnum(fieldVariable, field.type.baseName, field.type.isNullable)});');
         } else {
           indent.writeln(
-              '$result.$setter(${_castObject(field, root.classes, root.enums, fieldVariable)});');
+              '$result.$setter(${_castObject(field, fieldVariable)});');
         }
       });
       indent.writeln('return $result;');
@@ -412,7 +395,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     /// Returns an argument name that can be used in a context where it is possible to collide
     /// and append `.index` to enums.
     String getEnumSafeArgumentExpression(int count, NamedType argument) {
-      if (isEnum(root, argument.type)) {
+      if (argument.type.isEnum) {
         return argument.type.isNullable
             ? '${_getArgumentName(count, argument)}Arg == null ? null : ${_getArgumentName(count, argument)}Arg.index'
             : '${_getArgumentName(count, argument)}Arg.index';
@@ -462,18 +445,18 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
         String sendArgument;
         addDocumentationComments(
             indent, func.documentationComments, _docCommentSpec);
-        if (func.arguments.isEmpty) {
+        if (func.parameters.isEmpty) {
           indent.write(
               'public void ${func.name}(@NonNull $resultType<$returnType> result) ');
           sendArgument = 'null';
         } else {
-          final Iterable<String> argTypes = func.arguments
+          final Iterable<String> argTypes = func.parameters
               .map((NamedType e) => _nullsafeJavaTypeForDartType(e.type));
           final Iterable<String> argNames =
-              indexMap(func.arguments, _getSafeArgumentName);
+              indexMap(func.parameters, _getSafeArgumentName);
           final Iterable<String> enumSafeArgNames =
-              indexMap(func.arguments, getEnumSafeArgumentExpression);
-          if (func.arguments.length == 1) {
+              indexMap(func.parameters, getEnumSafeArgumentExpression);
+          if (func.parameters.length == 1) {
             sendArgument =
                 'new ArrayList<Object>(Collections.singletonList(${enumSafeArgNames.first}))';
           } else {
@@ -527,7 +510,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
                     if (func.returnType.baseName == 'int') {
                       outputExpression =
                           'listReply.get(0) == null ? null : ((Number) listReply.get(0)).longValue();';
-                    } else if (isEnum(root, func.returnType)) {
+                    } else if (func.returnType.isEnum) {
                       if (func.returnType.isNullable) {
                         outputExpression =
                             'listReply.get(0) == null ? null : $returnType.values()[(int) listReply.get(0)];';
@@ -648,11 +631,11 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
         ? 'void'
         : _javaTypeForDartType(method.returnType);
     final List<String> argSignature = <String>[];
-    if (method.arguments.isNotEmpty) {
-      final Iterable<String> argTypes = method.arguments
+    if (method.parameters.isNotEmpty) {
+      final Iterable<String> argTypes = method.parameters
           .map((NamedType e) => _nullsafeJavaTypeForDartType(e.type));
       final Iterable<String> argNames =
-          method.arguments.map((NamedType e) => e.name);
+          method.parameters.map((NamedType e) => e.name);
       argSignature
           .addAll(map2(argTypes, argNames, (String argType, String argName) {
         return '$argType $argName';
@@ -721,10 +704,10 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
             indent.writeln(
                 'ArrayList<Object> wrapped = new ArrayList<Object>();');
             final List<String> methodArgument = <String>[];
-            if (method.arguments.isNotEmpty) {
+            if (method.parameters.isNotEmpty) {
               indent.writeln(
                   'ArrayList<Object> args = (ArrayList<Object>) message;');
-              enumerate(method.arguments, (int index, NamedType arg) {
+              enumerate(method.parameters, (int index, NamedType arg) {
                 // The StandardMessageCodec can give us [Integer, Long] for
                 // a Dart 'int'.  To keep things simple we just use 64bit
                 // longs in Pigeon with Java.
@@ -736,7 +719,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
                     ? '($argName == null) ? null : $argName.longValue()'
                     : argName;
                 String accessor = 'args.get($index)';
-                if (isEnum(root, arg.type)) {
+                if (arg.type.isEnum) {
                   accessor = _intToEnum(
                       accessor, arg.type.baseName, arg.type.isNullable);
                 } else if (argType != 'Object') {
@@ -749,7 +732,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
             if (method.isAsynchronous) {
               final String resultValue =
                   method.returnType.isVoid ? 'null' : 'result';
-              if (isEnum(root, method.returnType)) {
+              if (method.returnType.isEnum) {
                 enumTag = method.returnType.isNullable
                     ? ' == null ? null : $resultValue.index'
                     : '.index';
@@ -784,7 +767,7 @@ $resultType<$returnType> $resultName =
                   indent.writeln('$call;');
                   indent.writeln('wrapped.add(0, null);');
                 } else {
-                  if (isEnum(root, method.returnType)) {
+                  if (method.returnType.isEnum) {
                     enumTag = method.returnType.isNullable
                         ? ' == null ? null : output.index'
                         : '.index';
@@ -1083,14 +1066,12 @@ String _cast(String variable, {required String javaType}) {
 /// Casts variable named [varName] to the correct host datatype for [field].
 /// This is for use in codecs where we may have a map representation of an
 /// object.
-String _castObject(
-    NamedType field, List<Class> classes, List<Enum> enums, String varName) {
-  final HostDatatype hostDatatype = getFieldHostDatatype(field, classes, enums,
-      (TypeDeclaration x) => _javaTypeForBuiltinDartType(x));
+String _castObject(NamedType field, String varName) {
+  final HostDatatype hostDatatype = getFieldHostDatatype(
+      field, (TypeDeclaration x) => _javaTypeForBuiltinDartType(x));
   if (field.type.baseName == 'int') {
     return '($varName == null) ? null : (($varName instanceof Integer) ? (Integer) $varName : (${hostDatatype.datatype}) $varName)';
-  } else if (!hostDatatype.isBuiltin &&
-      classes.map((Class x) => x.name).contains(field.type.baseName)) {
+  } else if (field.type.isClass) {
     return '($varName == null) ? null : ${hostDatatype.datatype}.fromList((ArrayList<Object>) $varName)';
   } else {
     return _cast(varName, javaType: hostDatatype.datatype);
diff --git a/packages/pigeon/lib/kotlin_generator.dart b/packages/pigeon/lib/kotlin_generator.dart
index 6956cdcbe76..e8d69ebef5f 100644
--- a/packages/pigeon/lib/kotlin_generator.dart
+++ b/packages/pigeon/lib/kotlin_generator.dart
@@ -151,27 +151,23 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     KotlinOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final Set<String> customClassNames =
-        root.classes.map((Class x) => x.name).toSet();
-    final Set<String> customEnumNames =
-        root.enums.map((Enum x) => x.name).toSet();
-
     const List<String> generatedMessages = <String>[
       ' Generated class from Pigeon that represents data sent in messages.'
     ];
     indent.newln();
     addDocumentationComments(
-        indent, klass.documentationComments, _docCommentSpec,
+        indent, classDefinition.documentationComments, _docCommentSpec,
         generatorComments: generatedMessages);
 
-    indent.write('data class ${klass.name} ');
+    indent.write('data class ${classDefinition.name} ');
     indent.addScoped('(', '', () {
-      for (final NamedType element in getFieldsInSerializationOrder(klass)) {
+      for (final NamedType element
+          in getFieldsInSerializationOrder(classDefinition)) {
         _writeClassField(indent, element);
-        if (getFieldsInSerializationOrder(klass).last != element) {
+        if (getFieldsInSerializationOrder(classDefinition).last != element) {
           indent.addln(',');
         } else {
           indent.newln();
@@ -184,18 +180,14 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
       writeClassEncode(
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
     });
@@ -206,25 +198,22 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     KotlinOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     indent.write('fun toList(): List<Any?> ');
     indent.addScoped('{', '}', () {
       indent.write('return listOf<Any?>');
       indent.addScoped('(', ')', () {
-        for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+        for (final NamedType field
+            in getFieldsInSerializationOrder(classDefinition)) {
           final HostDatatype hostDatatype = _getHostDatatype(root, field);
           String toWriteValue = '';
           final String fieldName = field.name;
           final String safeCall = field.type.isNullable ? '?' : '';
-          if (!hostDatatype.isBuiltin &&
-              customClassNames.contains(field.type.baseName)) {
+          if (field.type.isClass) {
             toWriteValue = '$fieldName$safeCall.toList()';
-          } else if (!hostDatatype.isBuiltin &&
-              customEnumNames.contains(field.type.baseName)) {
+          } else if (!hostDatatype.isBuiltin && field.type.isEnum) {
             toWriteValue = '$fieldName$safeCall.raw';
           } else {
             toWriteValue = fieldName;
@@ -240,12 +229,10 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     KotlinOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final String className = klass.name;
+    final String className = classDefinition.name;
 
     indent.write('companion object ');
     indent.addScoped('{', '}', () {
@@ -253,23 +240,19 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
       indent.write('fun fromList(list: List<Any?>): $className ');
 
       indent.addScoped('{', '}', () {
-        enumerate(getFieldsInSerializationOrder(klass),
+        enumerate(getFieldsInSerializationOrder(classDefinition),
             (int index, final NamedType field) {
-          final HostDatatype hostDatatype = _getHostDatatype(root, field);
-
           final String listValue = 'list[$index]';
           final String fieldType = _kotlinTypeForDartType(field.type);
 
           if (field.type.isNullable) {
-            if (!hostDatatype.isBuiltin &&
-                customClassNames.contains(field.type.baseName)) {
+            if (field.type.isClass) {
               indent.write('val ${field.name}: $fieldType? = ');
               indent.add('($listValue as List<Any?>?)?.let ');
               indent.addScoped('{', '}', () {
                 indent.writeln('$fieldType.fromList(it)');
               });
-            } else if (!hostDatatype.isBuiltin &&
-                customEnumNames.contains(field.type.baseName)) {
+            } else if (field.type.isEnum) {
               indent.write('val ${field.name}: $fieldType? = ');
               indent.add('($listValue as Int?)?.let ');
               indent.addScoped('{', '}', () {
@@ -277,28 +260,29 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
               });
             } else {
               indent.writeln(
-                  'val ${field.name} = ${_cast(root, indent, listValue, type: field.type)}');
+                  'val ${field.name} = ${_cast(indent, listValue, type: field.type)}');
             }
           } else {
-            if (!hostDatatype.isBuiltin &&
-                customClassNames.contains(field.type.baseName)) {
+            if (field.type.isClass) {
               indent.writeln(
                   'val ${field.name} = $fieldType.fromList($listValue as List<Any?>)');
-            } else if (!hostDatatype.isBuiltin &&
-                customEnumNames.contains(field.type.baseName)) {
+            } else if (field.type.isEnum) {
               indent.writeln(
                   'val ${field.name} = $fieldType.ofRaw($listValue as Int)!!');
             } else {
               indent.writeln(
-                  'val ${field.name} = ${_cast(root, indent, listValue, type: field.type)}');
+                  'val ${field.name} = ${_cast(indent, listValue, type: field.type)}');
             }
           }
         });
 
         indent.write('return $className(');
-        for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+        for (final NamedType field
+            in getFieldsInSerializationOrder(classDefinition)) {
           final String comma =
-              getFieldsInSerializationOrder(klass).last == field ? '' : ', ';
+              getFieldsInSerializationOrder(classDefinition).last == field
+                  ? ''
+                  : ', ';
           indent.add('${field.name}$comma');
         }
         indent.addln(')');
@@ -383,19 +367,19 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         addDocumentationComments(
             indent, func.documentationComments, _docCommentSpec);
 
-        if (func.arguments.isEmpty) {
+        if (func.parameters.isEmpty) {
           indent.write(
               'fun ${func.name}(callback: (Result<$returnType>) -> Unit) ');
           sendArgument = 'null';
         } else {
-          final Iterable<String> argTypes = func.arguments
+          final Iterable<String> argTypes = func.parameters
               .map((NamedType e) => _nullsafeKotlinTypeForDartType(e.type));
           final Iterable<String> argNames =
-              indexMap(func.arguments, _getSafeArgumentName);
+              indexMap(func.parameters, _getSafeArgumentName);
           final Iterable<String> enumSafeArgNames = indexMap(
-              func.arguments,
+              func.parameters,
               (int count, NamedType type) =>
-                  _getEnumSafeArgumentExpression(root, count, type));
+                  _getEnumSafeArgumentExpression(count, type));
           sendArgument = 'listOf(${enumSafeArgNames.join(', ')})';
           final String argsSignature = map2(argTypes, argNames,
               (String type, String name) => '$name: $type').join(', ');
@@ -426,15 +410,14 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
                 } else {
                   const String output = 'output';
                   // Nullable enums require special handling.
-                  if (isEnum(root, func.returnType) &&
-                      func.returnType.isNullable) {
+                  if (func.returnType.isEnum && func.returnType.isNullable) {
                     indent.writeScoped(
                         'val $output = (it[0] as Int?)?.let {', '}', () {
                       indent.writeln('${func.returnType.baseName}.ofRaw(it)');
                     });
                   } else {
                     indent.writeln(
-                        'val $output = ${_cast(root, indent, 'it[0]', type: func.returnType)}');
+                        'val $output = ${_cast(indent, 'it[0]', type: func.returnType)}');
                   }
                   indent.writeln('callback(Result.success($output))');
                 }
@@ -486,11 +469,11 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     indent.addScoped('{', '}', () {
       for (final Method method in api.methods) {
         final List<String> argSignature = <String>[];
-        if (method.arguments.isNotEmpty) {
-          final Iterable<String> argTypes = method.arguments
+        if (method.parameters.isNotEmpty) {
+          final Iterable<String> argTypes = method.parameters
               .map((NamedType e) => _nullsafeKotlinTypeForDartType(e.type));
           final Iterable<String> argNames =
-              method.arguments.map((NamedType e) => e.name);
+              method.parameters.map((NamedType e) => e.name);
           argSignature.addAll(
               map2(argTypes, argNames, (String argType, String argName) {
             return '$argName: $argType';
@@ -560,18 +543,18 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
               indent.write('if (api != null) ');
               indent.addScoped('{', '}', () {
                 final String messageVarName =
-                    method.arguments.isNotEmpty ? 'message' : '_';
+                    method.parameters.isNotEmpty ? 'message' : '_';
 
                 indent.write('channel.setMessageHandler ');
                 indent.addScoped('{ $messageVarName, reply ->', '}', () {
                   final List<String> methodArguments = <String>[];
-                  if (method.arguments.isNotEmpty) {
+                  if (method.parameters.isNotEmpty) {
                     indent.writeln('val args = message as List<Any?>');
-                    enumerate(method.arguments, (int index, NamedType arg) {
+                    enumerate(method.parameters, (int index, NamedType arg) {
                       final String argName = _getSafeArgumentName(index, arg);
                       final String argIndex = 'args[$index]';
                       indent.writeln(
-                          'val $argName = ${_castForceUnwrap(argIndex, arg.type, root, indent)}');
+                          'val $argName = ${_castForceUnwrap(argIndex, arg.type, indent)}');
                       methodArguments.add(argName);
                     });
                   }
@@ -592,7 +575,7 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
                       indent.addScoped(' else {', '}', () {
                         final String enumTagNullablePrefix =
                             method.returnType.isNullable ? '?' : '!!';
-                        final String enumTag = isEnum(root, method.returnType)
+                        final String enumTag = method.returnType.isEnum
                             ? '$enumTagNullablePrefix.raw'
                             : '';
                         if (method.returnType.isVoid) {
@@ -613,7 +596,7 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
                         indent.writeln('wrapped = listOf<Any?>(null)');
                       } else {
                         String enumTag = '';
-                        if (isEnum(root, method.returnType)) {
+                        if (method.returnType.isEnum) {
                           final String safeUnwrap =
                               method.returnType.isNullable ? '?' : '';
                           enumTag = '$safeUnwrap.raw';
@@ -773,8 +756,8 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
 }
 
 HostDatatype _getHostDatatype(Root root, NamedType field) {
-  return getFieldHostDatatype(field, root.classes, root.enums,
-      (TypeDeclaration x) => _kotlinTypeForBuiltinDartType(x));
+  return getFieldHostDatatype(
+      field, (TypeDeclaration x) => _kotlinTypeForBuiltinDartType(x));
 }
 
 /// Calculates the name of the codec that will be generated for [api].
@@ -785,9 +768,8 @@ String _getArgumentName(int count, NamedType argument) =>
 
 /// Returns an argument name that can be used in a context where it is possible to collide
 /// and append `.index` to enums.
-String _getEnumSafeArgumentExpression(
-    Root root, int count, NamedType argument) {
-  if (isEnum(root, argument.type)) {
+String _getEnumSafeArgumentExpression(int count, NamedType argument) {
+  if (argument.type.isEnum) {
     return argument.type.isNullable
         ? '${_getArgumentName(count, argument)}Arg?.raw'
         : '${_getArgumentName(count, argument)}Arg.raw';
@@ -799,15 +781,14 @@ String _getEnumSafeArgumentExpression(
 String _getSafeArgumentName(int count, NamedType argument) =>
     '${_getArgumentName(count, argument)}Arg';
 
-String _castForceUnwrap(
-    String value, TypeDeclaration type, Root root, Indent indent) {
-  if (isEnum(root, type)) {
+String _castForceUnwrap(String value, TypeDeclaration type, Indent indent) {
+  if (type.isEnum) {
     final String forceUnwrap = type.isNullable ? '' : '!!';
     final String nullableConditionPrefix =
         type.isNullable ? 'if ($value == null) null else ' : '';
     return '$nullableConditionPrefix${_kotlinTypeForDartType(type)}.ofRaw($value as Int)$forceUnwrap';
   } else {
-    return _cast(root, indent, value, type: type);
+    return _cast(indent, value, type: type);
   }
 }
 
@@ -872,8 +853,7 @@ String _nullsafeKotlinTypeForDartType(TypeDeclaration type) {
 }
 
 /// Returns an expression to cast [variable] to [kotlinType].
-String _cast(Root root, Indent indent, String variable,
-    {required TypeDeclaration type}) {
+String _cast(Indent indent, String variable, {required TypeDeclaration type}) {
   // Special-case Any, since no-op casts cause warnings.
   final String typeString = _kotlinTypeForDartType(type);
   if (type.isNullable && typeString == 'Any') {
@@ -882,7 +862,7 @@ String _cast(Root root, Indent indent, String variable,
   if (typeString == 'Int' || typeString == 'Long') {
     return '$variable${_castInt(type.isNullable)}';
   }
-  if (isEnum(root, type)) {
+  if (type.isEnum) {
     if (type.isNullable) {
       return '($variable as Int?)?.let {\n'
           '${indent.str}  $typeString.ofRaw(it)\n'
diff --git a/packages/pigeon/lib/objc_generator.dart b/packages/pigeon/lib/objc_generator.dart
index 96c02bf26dd..903957d083c 100644
--- a/packages/pigeon/lib/objc_generator.dart
+++ b/packages/pigeon/lib/objc_generator.dart
@@ -178,9 +178,9 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     required String dartPackageName,
   }) {
     indent.newln();
-    for (final Class klass in root.classes) {
+    for (final Class classDefinition in root.classes) {
       indent.writeln(
-          '@class ${_className(generatorOptions.prefix, klass.name)};');
+          '@class ${_className(generatorOptions.prefix, classDefinition.name)};');
     }
     indent.newln();
     super.writeDataClasses(
@@ -196,20 +196,20 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     final List<Class> classes = root.classes;
     final List<Enum> enums = root.enums;
     final String? prefix = generatorOptions.prefix;
-    final List<String> customEnumNames = enums.map((Enum x) => x.name).toList();
 
     addDocumentationComments(
-        indent, klass.documentationComments, _docCommentSpec);
+        indent, classDefinition.documentationComments, _docCommentSpec);
 
-    indent.writeln('@interface ${_className(prefix, klass.name)} : NSObject');
-    if (getFieldsInSerializationOrder(klass).isNotEmpty) {
-      if (getFieldsInSerializationOrder(klass)
+    indent.writeln(
+        '@interface ${_className(prefix, classDefinition.name)} : NSObject');
+    if (getFieldsInSerializationOrder(classDefinition).isNotEmpty) {
+      if (getFieldsInSerializationOrder(classDefinition)
           .map((NamedType e) => !e.type.isNullable)
           .any((bool e) => e)) {
         indent.writeln(
@@ -220,31 +220,29 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
         indent,
         generatorOptions,
         root,
-        klass,
+        classDefinition,
         classes,
         enums,
         prefix,
       );
       indent.addln(';');
     }
-    for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+    for (final NamedType field
+        in getFieldsInSerializationOrder(classDefinition)) {
       final HostDatatype hostDatatype = getFieldHostDatatype(
           field,
-          classes,
-          enums,
           (TypeDeclaration x) => _objcTypeStringForPrimitiveDartType(prefix, x,
               beforeString: true),
-          customResolver: customEnumNames.contains(field.type.baseName)
+          customResolver: field.type.isEnum
               ? (String x) => _enumName(x, prefix: prefix)
               : (String x) => '${_className(prefix, x)} *');
       late final String propertyType;
       addDocumentationComments(
           indent, field.documentationComments, _docCommentSpec);
       propertyType = _propertyTypeForDartType(field.type,
-          isNullable: field.type.isNullable,
-          isEnum: customEnumNames.contains(field.type.baseName));
+          isNullable: field.type.isNullable, isEnum: field.type.isEnum);
       final String nullability = field.type.isNullable ? ', nullable' : '';
-      final String fieldType = isEnum(root, field.type) && field.type.isNullable
+      final String fieldType = field.type.isEnum && field.type.isNullable
           ? _enumName(field.type.baseName,
               suffix: ' *',
               prefix: generatorOptions.prefix,
@@ -262,9 +260,7 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {}
 
@@ -273,9 +269,7 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {}
 
@@ -318,7 +312,7 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
         forceNullability: true,
       );
       final String callbackType =
-          _callbackForType(root, func.returnType, returnType, generatorOptions);
+          _callbackForType(func.returnType, returnType, generatorOptions);
       addDocumentationComments(
           indent, func.documentationComments, _docCommentSpec);
 
@@ -328,8 +322,6 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
         returnType: 'void',
         lastArgName: 'completion',
         lastArgType: callbackType,
-        isEnum: (TypeDeclaration t) => isEnum(root, t),
-        root: root,
       )};');
     }
     indent.writeln('@end');
@@ -377,7 +369,7 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
         lastArgName = 'completion';
         if (func.returnType.isVoid) {
           lastArgType = 'void (^)(FlutterError *_Nullable)';
-        } else if (isEnum(root, func.returnType)) {
+        } else if (func.returnType.isEnum) {
           lastArgType = 'void (^)($enumReturnType, FlutterError *_Nullable)';
         } else {
           lastArgType =
@@ -386,7 +378,7 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
       } else {
         if (func.returnType.isVoid) {
           returnType = 'void';
-        } else if (isEnum(root, func.returnType)) {
+        } else if (func.returnType.isEnum) {
           returnType = enumReturnType;
         } else {
           returnType = 'nullable $returnTypeName';
@@ -411,8 +403,6 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
         returnType: returnType,
         lastArgName: lastArgName,
         lastArgType: lastArgType,
-        isEnum: (TypeDeclaration t) => isEnum(root, t),
-        root: root,
       );
       indent.writeln('$signature;');
     }
@@ -500,8 +490,9 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     Indent indent, {
     required String dartPackageName,
   }) {
-    for (final Class klass in root.classes) {
-      _writeObjcSourceDataClassExtension(generatorOptions, indent, klass);
+    for (final Class classDefinition in root.classes) {
+      _writeObjcSourceDataClassExtension(
+          generatorOptions, indent, classDefinition);
     }
     indent.newln();
     super.writeDataClasses(
@@ -517,34 +508,31 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     final Set<String> customClassNames =
         root.classes.map((Class x) => x.name).toSet();
     final Set<String> customEnumNames =
         root.enums.map((Enum x) => x.name).toSet();
-    final String className = _className(generatorOptions.prefix, klass.name);
+    final String className =
+        _className(generatorOptions.prefix, classDefinition.name);
 
     indent.writeln('@implementation $className');
-    _writeObjcSourceClassInitializer(generatorOptions, root, indent, klass,
-        customClassNames, customEnumNames, className);
+    _writeObjcSourceClassInitializer(generatorOptions, root, indent,
+        classDefinition, customClassNames, customEnumNames, className);
     writeClassDecode(
       generatorOptions,
       root,
       indent,
-      klass,
-      customClassNames,
-      customEnumNames,
+      classDefinition,
       dartPackageName: dartPackageName,
     );
     writeClassEncode(
       generatorOptions,
       root,
       indent,
-      klass,
-      customClassNames,
-      customEnumNames,
+      classDefinition,
       dartPackageName: dartPackageName,
     );
     indent.writeln('@end');
@@ -556,18 +544,15 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     indent.write('- (NSArray *)toList ');
     indent.addScoped('{', '}', () {
       indent.write('return');
       indent.addScoped(' @[', '];', () {
-        for (final NamedType field in klass.fields) {
-          indent.writeln(
-              '${_arrayValue(customClassNames, customEnumNames, field)},');
+        for (final NamedType field in classDefinition.fields) {
+          indent.writeln('${_arrayValue(field)},');
         }
       });
     });
@@ -578,23 +563,22 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final String className = _className(generatorOptions.prefix, klass.name);
+    final String className =
+        _className(generatorOptions.prefix, classDefinition.name);
     indent.write('+ ($className *)fromList:(NSArray *)list ');
     indent.addScoped('{', '}', () {
       const String resultName = 'pigeonResult';
       indent.writeln('$className *$resultName = [[$className alloc] init];');
-      enumerate(getFieldsInSerializationOrder(klass),
+      enumerate(getFieldsInSerializationOrder(classDefinition),
           (int index, final NamedType field) {
-        final bool isEnumType = customEnumNames.contains(field.type.baseName);
-        final String valueGetter = _listGetter(
-            customClassNames, 'list', field, index, generatorOptions.prefix);
+        final bool isEnumType = field.type.isEnum;
+        final String valueGetter =
+            _listGetter('list', field, index, generatorOptions.prefix);
         final String? primitiveExtractionMethod =
-            _nsnumberExtractionMethod(field.type, isEnum: isEnumType);
+            _nsnumberExtractionMethod(field.type);
         final String ivarValueExpression;
         if (primitiveExtractionMethod != null) {
           ivarValueExpression = '[$valueGetter $primitiveExtractionMethod]';
@@ -766,19 +750,19 @@ static FlutterError *createConnectionError(NSString *channelName) {
     void unpackArgs(String variable) {
       indent.writeln('NSArray *args = $variable;');
       int count = 0;
-      for (final NamedType arg in func.arguments) {
+      for (final NamedType arg in func.parameters) {
         final String argName = _getSafeArgName(count, arg);
-        final bool isEnumType = isEnum(root, arg.type);
         final String valueGetter = 'GetNullableObjectAtIndex(args, $count)';
         final String? primitiveExtractionMethod =
-            _nsnumberExtractionMethod(arg.type, isEnum: isEnumType);
+            _nsnumberExtractionMethod(arg.type);
         final _ObjcType objcArgType = _objcTypeForDartType(
-            generatorOptions.prefix, arg.type,
-            isEnum: isEnumType);
+          generatorOptions.prefix,
+          arg.type,
+        );
         if (primitiveExtractionMethod != null) {
           indent.writeln(
               '${objcArgType.beforeString}$argName = [$valueGetter $primitiveExtractionMethod];');
-        } else if (isEnumType) {
+        } else if (arg.type.isEnum) {
           indent.writeln('NSNumber *${argName}AsNumber = $valueGetter;');
           indent.writeln(
               '${_enumName(arg.type.baseName, suffix: ' *', prefix: '', box: true)}$argName = ${argName}AsNumber == nil ? nil : [[${_enumName(arg.type.baseName, prefix: generatorOptions.prefix, box: true)} alloc] initWithValue:[${argName}AsNumber integerValue]];');
@@ -793,7 +777,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
         String callSignature, _ObjcType returnType) {
       if (func.returnType.isVoid) {
         const String callback = 'callback(wrapResult(nil, error));';
-        if (func.arguments.isEmpty) {
+        if (func.parameters.isEmpty) {
           indent.writeScoped(
               '[api ${selectorComponents.first}:^(FlutterError *_Nullable error) {',
               '}];', () {
@@ -813,15 +797,15 @@ static FlutterError *createConnectionError(NSString *channelName) {
         const String enumConversionExpression =
             'enumValue == nil ? nil : [NSNumber numberWithInteger:enumValue.value];';
 
-        if (isEnum(root, func.returnType)) {
+        if (func.returnType.isEnum) {
           returnTypeString =
               '${_enumName(returnType.baseName, suffix: ' *_Nullable', prefix: generatorOptions.prefix, box: true)} enumValue';
         }
-        if (func.arguments.isEmpty) {
+        if (func.parameters.isEmpty) {
           indent.writeScoped(
               '[api ${selectorComponents.first}:^($returnTypeString, FlutterError *_Nullable error) {',
               '}];', () {
-            if (isEnum(root, func.returnType)) {
+            if (func.returnType.isEnum) {
               indent.writeln('$numberOutput $enumConversionExpression');
             }
             indent.writeln(callback);
@@ -830,7 +814,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
           indent.writeScoped(
               '[api $callSignature ${selectorComponents.last}:^($returnTypeString, FlutterError *_Nullable error) {',
               '}];', () {
-            if (isEnum(root, func.returnType)) {
+            if (func.returnType.isEnum) {
               indent.writeln('$numberOutput $enumConversionExpression');
             }
             indent.writeln(callback);
@@ -845,7 +829,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
         indent.writeln('$call;');
         indent.writeln('callback(wrapResult(nil, error));');
       } else {
-        if (isEnum(root, func.returnType)) {
+        if (func.returnType.isEnum) {
           indent.writeln(
               '${_enumName(func.returnType.baseName, suffix: ' *', prefix: generatorOptions.prefix, box: true)} enumBox = $call;');
           indent.writeln(
@@ -874,19 +858,19 @@ static FlutterError *createConnectionError(NSString *channelName) {
       final Iterable<String> selectorComponents =
           _getSelectorComponents(func, lastSelectorComponent);
       final Iterable<String> argNames =
-          indexMap(func.arguments, _getSafeArgName);
+          indexMap(func.parameters, _getSafeArgName);
       final String callSignature =
           map2(selectorComponents.take(argNames.length), argNames,
               (String selectorComponent, String argName) {
         return '$selectorComponent:$argName';
       }).join(' ');
-      if (func.arguments.isNotEmpty) {
+      if (func.parameters.isNotEmpty) {
         unpackArgs('message');
       }
       if (func.isAsynchronous) {
         writeAsyncBindings(selectorComponents, callSignature, returnType);
       } else {
-        final String syncCall = func.arguments.isEmpty
+        final String syncCall = func.parameters.isEmpty
             ? '[api ${selectorComponents.first}:&error]'
             : '[api $callSignature error:&error]';
         writeSyncBindings(syncCall, returnType);
@@ -925,8 +909,9 @@ static FlutterError *createConnectionError(NSString *channelName) {
   }
 
   void _writeObjcSourceDataClassExtension(
-      ObjcOptions languageOptions, Indent indent, Class klass) {
-    final String className = _className(languageOptions.prefix, klass.name);
+      ObjcOptions languageOptions, Indent indent, Class classDefinition) {
+    final String className =
+        _className(languageOptions.prefix, classDefinition.name);
     indent.newln();
     indent.writeln('@interface $className ()');
     indent.writeln('+ ($className *)fromList:(NSArray *)list;');
@@ -940,7 +925,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
     ObjcOptions languageOptions,
     Root root,
     Indent indent,
-    Class klass,
+    Class classDefinition,
     Set<String> customClassNames,
     Set<String> customEnumNames,
     String className,
@@ -949,7 +934,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
       indent,
       languageOptions,
       root,
-      klass,
+      classDefinition,
       root.classes,
       root.enums,
       languageOptions.prefix,
@@ -957,7 +942,8 @@ static FlutterError *createConnectionError(NSString *channelName) {
     indent.writeScoped(' {', '}', () {
       const String result = 'pigeonResult';
       indent.writeln('$className* $result = [[$className alloc] init];');
-      for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+      for (final NamedType field
+          in getFieldsInSerializationOrder(classDefinition)) {
         indent.writeln('$result.${field.name} = ${field.name};');
       }
       indent.writeln('return $result;');
@@ -1082,20 +1068,18 @@ static FlutterError *createConnectionError(NSString *channelName) {
       forceNullability: true,
     );
     final String callbackType =
-        _callbackForType(root, func.returnType, returnType, languageOptions);
+        _callbackForType(func.returnType, returnType, languageOptions);
 
     String argNameFunc(int count, NamedType arg) => _getSafeArgName(count, arg);
     String sendArgument;
-    if (func.arguments.isEmpty) {
+    if (func.parameters.isEmpty) {
       sendArgument = 'nil';
     } else {
       int count = 0;
       String makeVarOrNSNullExpression(NamedType arg) {
         final String argName = argNameFunc(count, arg);
-        final bool isEnumType = isEnum(root, arg.type);
-        String varExpression =
-            _collectionSafeExpression(argName, arg.type, isEnum: isEnumType);
-        if (isEnumType) {
+        String varExpression = _collectionSafeExpression(argName, arg.type);
+        if (arg.type.isEnum) {
           if (arg.type.isNullable) {
             varExpression =
                 '${argNameFunc(count, arg)} == nil ? [NSNull null] : [NSNumber numberWithInteger:$argName.value]';
@@ -1108,7 +1092,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
       }
 
       sendArgument =
-          '@[${func.arguments.map(makeVarOrNSNullExpression).join(', ')}]';
+          '@[${func.parameters.map(makeVarOrNSNullExpression).join(', ')}]';
     }
     indent.write(_makeObjcSignature(
       func: func,
@@ -1117,8 +1101,6 @@ static FlutterError *createConnectionError(NSString *channelName) {
       lastArgName: 'completion',
       lastArgType: callbackType,
       argNameFunc: argNameFunc,
-      isEnum: (TypeDeclaration t) => isEnum(root, t),
-      root: root,
     ));
     indent.addScoped(' {', '}', () {
       indent.writeln(
@@ -1149,7 +1131,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
             if (func.returnType.isVoid) {
               indent.writeln('completion(nil);');
             } else {
-              if (isEnum(root, func.returnType)) {
+              if (func.returnType.isEnum) {
                 final String enumName = _enumName(returnType.baseName,
                     prefix: languageOptions.prefix, box: true);
                 indent.writeln('NSNumber *outputAsNumber = $nullCheck;');
@@ -1179,15 +1161,15 @@ void _writeObjcSourceClassInitializerDeclaration(
     Indent indent,
     ObjcOptions generatorOptions,
     Root root,
-    Class klass,
+    Class classDefinition,
     List<Class> classes,
     List<Enum> enums,
     String? prefix) {
-  final List<String> customEnumNames = enums.map((Enum x) => x.name).toList();
   indent.write('+ (instancetype)makeWith');
   bool isFirst = true;
   indent.nest(2, () {
-    for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+    for (final NamedType field
+        in getFieldsInSerializationOrder(classDefinition)) {
       final String label = isFirst ? _capitalize(field.name) : field.name;
       final void Function(String) printer = isFirst
           ? indent.add
@@ -1198,11 +1180,9 @@ void _writeObjcSourceClassInitializerDeclaration(
       isFirst = false;
       final HostDatatype hostDatatype = getFieldHostDatatype(
           field,
-          classes,
-          enums,
           (TypeDeclaration x) => _objcTypeStringForPrimitiveDartType(prefix, x,
               beforeString: true),
-          customResolver: customEnumNames.contains(field.type.baseName)
+          customResolver: field.type.isEnum
               ? (String x) => field.type.isNullable
                   ? _enumName(x, suffix: ' *', prefix: prefix, box: true)
                   : _enumName(x, prefix: prefix)
@@ -1228,10 +1208,10 @@ String _className(String? prefix, String className) {
 
 /// Calculates callback block signature for async methods.
 String _callbackForType(
-    Root root, TypeDeclaration type, _ObjcType objcType, ObjcOptions options) {
+    TypeDeclaration type, _ObjcType objcType, ObjcOptions options) {
   if (type.isVoid) {
     return 'void (^)(FlutterError *_Nullable)';
-  } else if (isEnum(root, type)) {
+  } else if (type.isEnum) {
     return 'void (^)(${_enumName(objcType.baseName, suffix: ' *_Nullable', prefix: options.prefix, box: true)}, FlutterError *_Nullable)';
   } else {
     return 'void (^)(${objcType.beforeString}_Nullable, FlutterError *_Nullable)';
@@ -1287,10 +1267,10 @@ const Map<String, _ObjcType> _objcTypeForNonNullableDartTypeMap =
   'Object': _ObjcType(baseName: 'id'),
 };
 
-bool _usesPrimitive(TypeDeclaration type, {required bool isEnum}) {
+bool _usesPrimitive(TypeDeclaration type) {
   // Only non-nullable types are unboxed.
   if (!type.isNullable) {
-    if (isEnum) {
+    if (type.isEnum) {
       return true;
     }
     switch (type.baseName) {
@@ -1303,20 +1283,23 @@ bool _usesPrimitive(TypeDeclaration type, {required bool isEnum}) {
   return false;
 }
 
-String _collectionSafeExpression(String expression, TypeDeclaration type,
-    {required bool isEnum}) {
-  return _usesPrimitive(type, isEnum: isEnum)
+String _collectionSafeExpression(
+  String expression,
+  TypeDeclaration type,
+) {
+  return _usesPrimitive(type)
       ? '@($expression)'
       : '$expression ?: [NSNull null]';
 }
 
 /// Returns the method to convert [type] from a boxed NSNumber to its
 /// corresponding primitive value, if any.
-String? _nsnumberExtractionMethod(TypeDeclaration type,
-    {required bool isEnum}) {
+String? _nsnumberExtractionMethod(
+  TypeDeclaration type,
+) {
   // Only non-nullable types are unboxed.
   if (!type.isNullable) {
-    if (isEnum) {
+    if (type.isEnum) {
       return 'integerValue';
     }
     switch (type.baseName) {
@@ -1368,14 +1351,14 @@ String? _objcTypeStringForPrimitiveDartType(
 /// Returns the Objective-C type for a Dart [field], prepending the
 /// [classPrefix] for generated classes.
 _ObjcType _objcTypeForDartType(String? classPrefix, TypeDeclaration field,
-    {bool isEnum = false, bool forceNullability = false}) {
+    {bool forceNullability = false}) {
   final _ObjcType? primitiveType =
       _objcTypeForPrimitiveDartType(field, forceNullability: forceNullability);
   return primitiveType == null
       ? _ObjcType(
           baseName: _className(classPrefix, field.baseName),
           // Non-nullable enums are non-pointer types.
-          isPointer: !isEnum || (field.isNullable || forceNullability))
+          isPointer: !field.isEnum || (field.isNullable || forceNullability))
       : field.typeArguments.isEmpty
           ? primitiveType
           : _ObjcType(
@@ -1428,24 +1411,24 @@ String _capitalize(String str) =>
 Iterable<String> _getSelectorComponents(
     Method func, String lastSelectorComponent) sync* {
   if (func.objcSelector.isEmpty) {
-    final Iterator<NamedType> it = func.arguments.iterator;
+    final Iterator<NamedType> it = func.parameters.iterator;
     final bool hasArguments = it.moveNext();
     final String namePostfix =
-        (lastSelectorComponent.isNotEmpty && func.arguments.isEmpty)
+        (lastSelectorComponent.isNotEmpty && func.parameters.isEmpty)
             ? 'With${_capitalize(lastSelectorComponent)}'
             : '';
-    yield '${func.name}${hasArguments ? _capitalize(func.arguments[0].name) : namePostfix}';
+    yield '${func.name}${hasArguments ? _capitalize(func.parameters[0].name) : namePostfix}';
     while (it.moveNext()) {
       yield it.current.name;
     }
   } else {
-    assert(':'.allMatches(func.objcSelector).length == func.arguments.length);
+    assert(':'.allMatches(func.objcSelector).length == func.parameters.length);
     final Iterable<String> customComponents = func.objcSelector
         .split(':')
         .where((String element) => element.isNotEmpty);
     yield* customComponents;
   }
-  if (lastSelectorComponent.isNotEmpty && func.arguments.isNotEmpty) {
+  if (lastSelectorComponent.isNotEmpty && func.parameters.isNotEmpty) {
     yield lastSelectorComponent;
   }
 }
@@ -1457,27 +1440,25 @@ Iterable<String> _getSelectorComponents(
 /// [func].  This is typically used for passing in 'error' or 'completion'
 /// arguments that don't exist in the pigeon file but are required in the objc
 /// output.  [argNameFunc] is the function used to generate the argument name
-/// [func.arguments].
+/// [func.parameters].
 String _makeObjcSignature({
   required Method func,
   required ObjcOptions options,
   required String returnType,
   required String lastArgType,
   required String lastArgName,
-  required bool Function(TypeDeclaration) isEnum,
-  required Root root,
   String Function(int, NamedType)? argNameFunc,
 }) {
   argNameFunc = argNameFunc ??
       (int _, NamedType e) =>
-          e.type.isNullable && isEnum(e.type) ? '${e.name}Boxed' : e.name;
+          e.type.isNullable && e.type.isEnum ? '${e.name}Boxed' : e.name;
   final Iterable<String> argNames =
-      followedByOne(indexMap(func.arguments, argNameFunc), lastArgName);
+      followedByOne(indexMap(func.parameters, argNameFunc), lastArgName);
   final Iterable<String> selectorComponents =
       _getSelectorComponents(func, lastArgName);
   final Iterable<String> argTypes = followedByOne(
-    func.arguments.map((NamedType arg) {
-      if (isEnum(arg.type)) {
+    func.parameters.map((NamedType arg) {
+      if (arg.type.isEnum) {
         return '${arg.type.isNullable ? 'nullable ' : ''}${_enumName(arg.type.baseName, suffix: arg.type.isNullable ? ' *' : '', prefix: options.prefix, box: arg.type.isNullable)}';
       } else {
         final String nullable = arg.type.isNullable ? 'nullable ' : '';
@@ -1503,9 +1484,8 @@ String _makeObjcSignature({
 /// provided [options].
 void generateObjcHeader(ObjcOptions options, Root root, Indent indent) {}
 
-String _listGetter(Set<String> customClassNames, String list, NamedType field,
-    int index, String? prefix) {
-  if (customClassNames.contains(field.type.baseName)) {
+String _listGetter(String list, NamedType field, int index, String? prefix) {
+  if (field.type.isClass) {
     String className = field.type.baseName;
     if (prefix != null) {
       className = '$prefix$className';
@@ -1516,19 +1496,19 @@ String _listGetter(Set<String> customClassNames, String list, NamedType field,
   }
 }
 
-String _arrayValue(Set<String> customClassNames, Set<String> customEnumNames,
-    NamedType field) {
-  final bool isEnumType = customEnumNames.contains(field.type.baseName);
-  if (customClassNames.contains(field.type.baseName)) {
+String _arrayValue(NamedType field) {
+  if (field.type.isClass) {
     return '(self.${field.name} ? [self.${field.name} toList] : [NSNull null])';
-  } else if (isEnumType) {
+  } else if (field.type.isEnum) {
     if (field.type.isNullable) {
       return '(self.${field.name} == nil ? [NSNull null] : [NSNumber numberWithInteger:self.${field.name}.value])';
     }
     return '@(self.${field.name})';
   } else {
-    return _collectionSafeExpression('self.${field.name}', field.type,
-        isEnum: isEnumType);
+    return _collectionSafeExpression(
+      'self.${field.name}',
+      field.type,
+    );
   }
 }
 
@@ -1565,8 +1545,8 @@ List<Error> validateObjc(ObjcOptions options, Root root) {
   final List<Error> errors = <Error>[];
   for (final Api api in root.apis) {
     for (final Method method in api.methods) {
-      for (final NamedType arg in method.arguments) {
-        if (isEnum(root, arg.type) && arg.type.isNullable) {
+      for (final NamedType arg in method.parameters) {
+        if (arg.type.isEnum && arg.type.isNullable) {
           // TODO(gaaclarke): Add line number.
           errors.add(Error(
               message:
diff --git a/packages/pigeon/lib/pigeon_lib.dart b/packages/pigeon/lib/pigeon_lib.dart
index 81bbb90c04e..032cb691788 100644
--- a/packages/pigeon/lib/pigeon_lib.dart
+++ b/packages/pigeon/lib/pigeon_lib.dart
@@ -21,6 +21,7 @@ import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart' as dart_ast_visitor;
 import 'package:analyzer/error/error.dart' show AnalysisError;
 import 'package:args/args.dart';
+import 'package:collection/collection.dart' as collection;
 import 'package:path/path.dart' as path;
 
 import 'ast.dart';
@@ -756,20 +757,21 @@ List<Error> _validateAst(Root root, String source) {
   final List<String> customClasses =
       root.classes.map((Class x) => x.name).toList();
   final Iterable<String> customEnums = root.enums.map((Enum x) => x.name);
-  for (final Class klass in root.classes) {
-    for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+  for (final Class classDefinition in root.classes) {
+    for (final NamedType field
+        in getFieldsInSerializationOrder(classDefinition)) {
       for (final TypeDeclaration typeArgument in field.type.typeArguments) {
         if (!typeArgument.isNullable) {
           result.add(Error(
             message:
-                'Generic type arguments must be nullable in field "${field.name}" in class "${klass.name}".',
+                'Generic type parameters must be nullable in field "${field.name}" in class "${classDefinition.name}".',
             lineNumber: _calculateLineNumberNullable(source, field.offset),
           ));
         }
         if (customEnums.contains(typeArgument.baseName)) {
           result.add(Error(
             message:
-                'Enum types aren\'t supported in type arguments in "${field.name}" in class "${klass.name}".',
+                'Enum types aren\'t supported in type arguments in "${field.name}" in class "${classDefinition.name}".',
             lineNumber: _calculateLineNumberNullable(source, field.offset),
           ));
         }
@@ -779,7 +781,7 @@ List<Error> _validateAst(Root root, String source) {
           customEnums.contains(field.type.baseName))) {
         result.add(Error(
           message:
-              'Unsupported datatype:"${field.type.baseName}" in class "${klass.name}".',
+              'Unsupported datatype:"${field.type.baseName}" in class "${classDefinition.name}".',
           lineNumber: _calculateLineNumberNullable(source, field.offset),
         ));
       }
@@ -787,31 +789,44 @@ List<Error> _validateAst(Root root, String source) {
   }
   for (final Api api in root.apis) {
     for (final Method method in api.methods) {
-      for (final NamedType unnamedType in method.arguments
-          .where((NamedType element) => element.type.baseName.isEmpty)) {
-        result.add(Error(
-          message:
-              'Arguments must specify their type in method "${method.name}" in API: "${api.name}"',
-          lineNumber: _calculateLineNumberNullable(source, unnamedType.offset),
-        ));
+      for (final Parameter param in method.parameters) {
+        if (param.type.baseName.isEmpty) {
+          result.add(Error(
+            message:
+                'Parameters must specify their type in method "${method.name}" in API: "${api.name}"',
+            lineNumber: _calculateLineNumberNullable(source, param.offset),
+          ));
+        } else if (param.name.startsWith('__pigeon_')) {
+          result.add(Error(
+            message:
+                'Parameter name must not begin with "__pigeon_" in method "${method.name}" in API: "${api.name}"',
+            lineNumber: _calculateLineNumberNullable(source, param.offset),
+          ));
+        } else if (param.name == 'pigeonChannelCodec') {
+          result.add(Error(
+            message:
+                'Parameter name must not be "pigeonChannelCodec" in method "${method.name}" in API: "${api.name}"',
+            lineNumber: _calculateLineNumberNullable(source, param.offset),
+          ));
+        }
       }
       if (method.objcSelector.isNotEmpty) {
         if (':'.allMatches(method.objcSelector).length !=
-            method.arguments.length) {
+            method.parameters.length) {
           result.add(Error(
             message:
-                'Invalid selector, expected ${method.arguments.length} arguments.',
+                'Invalid selector, expected ${method.parameters.length} parameters.',
             lineNumber: _calculateLineNumberNullable(source, method.offset),
           ));
         }
       }
       if (method.swiftFunction.isNotEmpty) {
         final RegExp signatureRegex =
-            RegExp('\\w+ *\\((\\w+:){${method.arguments.length}}\\)');
+            RegExp('\\w+ *\\((\\w+:){${method.parameters.length}}\\)');
         if (!signatureRegex.hasMatch(method.swiftFunction)) {
           result.add(Error(
             message:
-                'Invalid function signature, expected ${method.arguments.length} arguments.',
+                'Invalid function signature, expected ${method.parameters.length} parameters.',
             lineNumber: _calculateLineNumberNullable(source, method.offset),
           ));
         }
@@ -850,6 +865,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
   final String source;
 
   Class? _currentClass;
+  Map<String, String> _currentClassDefaultValues = <String, String>{};
   Api? _currentApi;
   Map<String, Object>? _pigeonOptions;
 
@@ -864,6 +880,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     if (_currentClass != null) {
       _classes.add(_currentClass!);
       _currentClass = null;
+      _currentClassDefaultValues = <String, String>{};
     }
   }
 
@@ -908,6 +925,24 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
             lineNumber: lineNumber));
       }
     }
+    for (final Class classDefinition in referencedClasses) {
+      final List<NamedType> fields = <NamedType>[];
+      for (final NamedType field in classDefinition.fields) {
+        fields.add(field.copyWithType(_attachClassesAndEnums(field.type)));
+      }
+      classDefinition.fields = fields;
+    }
+
+    for (final Api api in _apis) {
+      for (final Method func in api.methods) {
+        final List<Parameter> paramList = <Parameter>[];
+        for (final Parameter param in func.parameters) {
+          paramList.add(param.copyWithType(_attachClassesAndEnums(param.type)));
+        }
+        func.parameters = paramList;
+        func.returnType = _attachClassesAndEnums(func.returnType);
+      }
+    }
 
     return ParseResults(
       root: totalErrors.isEmpty
@@ -918,6 +953,19 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     );
   }
 
+  TypeDeclaration _attachClassesAndEnums(TypeDeclaration type) {
+    final Enum? assocEnum = _enums.firstWhereOrNull(
+        (Enum enumDefinition) => enumDefinition.name == type.baseName);
+    final Class? assocClass = _classes.firstWhereOrNull(
+        (Class classDefinition) => classDefinition.name == type.baseName);
+    if (assocClass != null) {
+      return type.copyWithClass(assocClass);
+    } else if (assocEnum != null) {
+      return type.copyWithEnum(assocEnum);
+    }
+    return type;
+  }
+
   Object _expressionToMap(dart_ast.Expression expression) {
     if (expression is dart_ast.MethodInvocation) {
       final Map<String, Object> result = <String, Object>{};
@@ -1059,26 +1107,56 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
         <String>[];
   }
 
-  NamedType formalParameterToField(dart_ast.FormalParameter parameter) {
-    final dart_ast.NamedType? namedType =
-        getFirstChildOfType<dart_ast.NamedType>(parameter);
-    if (namedType != null) {
-      final String argTypeBaseName = _getNamedTypeQualifiedName(namedType);
-      final bool isNullable = namedType.question != null;
+  Parameter formalParameterToPigeonParameter(
+    dart_ast.FormalParameter formalParameter, {
+    bool? isNamed,
+    bool? isOptional,
+    bool? isPositional,
+    bool? isRequired,
+    String? defaultValue,
+  }) {
+    final dart_ast.NamedType? parameter =
+        getFirstChildOfType<dart_ast.NamedType>(formalParameter);
+    final dart_ast.SimpleFormalParameter? simpleFormalParameter =
+        getFirstChildOfType<dart_ast.SimpleFormalParameter>(formalParameter);
+    if (parameter != null) {
+      final String argTypeBaseName = _getNamedTypeQualifiedName(parameter);
+      final bool isNullable = parameter.question != null;
       final List<TypeDeclaration> argTypeArguments =
-          typeAnnotationsToTypeArguments(namedType.typeArguments);
-      return NamedType(
-          type: TypeDeclaration(
-              baseName: argTypeBaseName,
-              isNullable: isNullable,
-              typeArguments: argTypeArguments),
-          name: parameter.name?.lexeme ?? '',
-          offset: parameter.offset);
+          typeAnnotationsToTypeArguments(parameter.typeArguments);
+      return Parameter(
+        type: TypeDeclaration(
+          baseName: argTypeBaseName,
+          isNullable: isNullable,
+          typeArguments: argTypeArguments,
+        ),
+        name: formalParameter.name?.lexeme ?? '',
+        offset: formalParameter.offset,
+        isNamed: isNamed,
+        isOptional: isOptional,
+        isPositional: isPositional,
+        isRequired: isRequired,
+        defaultValue: defaultValue,
+      );
+    } else if (simpleFormalParameter != null) {
+      String? defaultValue;
+      if (formalParameter is dart_ast.DefaultFormalParameter) {
+        defaultValue = formalParameter.defaultValue?.toString();
+      }
+
+      return formalParameterToPigeonParameter(
+        simpleFormalParameter,
+        isNamed: simpleFormalParameter.isNamed,
+        isOptional: simpleFormalParameter.isOptional,
+        isPositional: simpleFormalParameter.isPositional,
+        isRequired: simpleFormalParameter.isRequired,
+        defaultValue: defaultValue,
+      );
     } else {
-      return NamedType(
+      return Parameter(
         name: '',
         type: const TypeDeclaration(baseName: '', isNullable: false),
-        offset: parameter.offset,
+        offset: formalParameter.offset,
       );
     }
   }
@@ -1108,8 +1186,8 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
   @override
   Object? visitMethodDeclaration(dart_ast.MethodDeclaration node) {
     final dart_ast.FormalParameterList parameters = node.parameters!;
-    final List<NamedType> arguments =
-        parameters.parameters.map(formalParameterToField).toList();
+    final List<Parameter> arguments =
+        parameters.parameters.map(formalParameterToPigeonParameter).toList();
     final bool isAsynchronous = _hasMetadata(node.metadata, 'async');
     final String objcSelector = _findMetadata(node.metadata, 'ObjCSelector')
             ?.arguments
@@ -1149,7 +1227,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
               typeArguments:
                   typeAnnotationsToTypeArguments(returnType.typeArguments),
               isNullable: returnType.question != null),
-          arguments: arguments,
+          parameters: arguments,
           isAsynchronous: isAsynchronous,
           objcSelector: objcSelector,
           swiftFunction: swiftFunction,
@@ -1222,17 +1300,20 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
               lineNumber: _calculateLineNumber(source, node.offset)));
         } else {
           final dart_ast.TypeArgumentList? typeArguments = type.typeArguments;
-          _currentClass!.fields.add(NamedType(
+          final String name = node.fields.variables[0].name.lexeme;
+          final NamedType field = NamedType(
             type: TypeDeclaration(
               baseName: _getNamedTypeQualifiedName(type),
               isNullable: type.question != null,
               typeArguments: typeAnnotationsToTypeArguments(typeArguments),
             ),
-            name: node.fields.variables[0].name.lexeme,
+            name: name,
             offset: node.offset,
+            defaultValue: _currentClassDefaultValues[name],
             documentationComments:
                 _documentationCommentsParser(node.documentationComment?.tokens),
-          ));
+          );
+          _currentClass!.fields.add(field);
         }
       } else {
         _errors.add(Error(
@@ -1265,6 +1346,16 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
             message:
                 'Constructor initializers aren\'t supported in data classes (use "this.fieldName") ("$node").',
             lineNumber: _calculateLineNumber(source, node.offset)));
+      } else {
+        for (final dart_ast.FormalParameter param
+            in node.parameters.parameters) {
+          if (param is dart_ast.DefaultFormalParameter) {
+            if (param.name != null && param.defaultValue != null) {
+              _currentClassDefaultValues[param.name!.toString()] =
+                  param.defaultValue!.toString();
+            }
+          }
+        }
       }
     }
     node.visitChildren(this);
diff --git a/packages/pigeon/lib/swift_generator.dart b/packages/pigeon/lib/swift_generator.dart
index 9fe23f2ce77..ae869426e62 100644
--- a/packages/pigeon/lib/swift_generator.dart
+++ b/packages/pigeon/lib/swift_generator.dart
@@ -113,25 +113,20 @@ import FlutterMacOS
     SwiftOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final Set<String> customClassNames =
-        root.classes.map((Class x) => x.name).toSet();
-    final Set<String> customEnumNames =
-        root.enums.map((Enum x) => x.name).toSet();
-
     const List<String> generatedComments = <String>[
       ' Generated class from Pigeon that represents data sent in messages.'
     ];
     indent.newln();
     addDocumentationComments(
-        indent, klass.documentationComments, _docCommentSpec,
+        indent, classDefinition.documentationComments, _docCommentSpec,
         generatorComments: generatedComments);
 
-    indent.write('struct ${klass.name} ');
+    indent.write('struct ${classDefinition.name} ');
     indent.addScoped('{', '}', () {
-      getFieldsInSerializationOrder(klass).forEach((NamedType field) {
+      getFieldsInSerializationOrder(classDefinition).forEach((NamedType field) {
         _writeClassField(indent, field);
       });
 
@@ -140,18 +135,14 @@ import FlutterMacOS
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
       writeClassEncode(
         generatorOptions,
         root,
         indent,
-        klass,
-        customClassNames,
-        customEnumNames,
+        classDefinition,
         dartPackageName: dartPackageName,
       );
     });
@@ -162,25 +153,21 @@ import FlutterMacOS
     SwiftOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
     indent.write('func toList() -> [Any?] ');
     indent.addScoped('{', '}', () {
       indent.write('return ');
       indent.addScoped('[', ']', () {
-        for (final NamedType field in getFieldsInSerializationOrder(klass)) {
-          final HostDatatype hostDatatype = _getHostDatatype(root, field);
+        for (final NamedType field
+            in getFieldsInSerializationOrder(classDefinition)) {
           String toWriteValue = '';
           final String fieldName = field.name;
           final String nullsafe = field.type.isNullable ? '?' : '';
-          if (!hostDatatype.isBuiltin &&
-              customClassNames.contains(field.type.baseName)) {
+          if (field.type.isClass) {
             toWriteValue = '$fieldName$nullsafe.toList()';
-          } else if (!hostDatatype.isBuiltin &&
-              customEnumNames.contains(field.type.baseName)) {
+          } else if (field.type.isEnum) {
             toWriteValue = '$fieldName$nullsafe.rawValue';
           } else {
             toWriteValue = field.name;
@@ -197,36 +184,34 @@ import FlutterMacOS
     SwiftOptions generatorOptions,
     Root root,
     Indent indent,
-    Class klass,
-    Set<String> customClassNames,
-    Set<String> customEnumNames, {
+    Class classDefinition, {
     required String dartPackageName,
   }) {
-    final String className = klass.name;
+    final String className = classDefinition.name;
     indent.write('static func fromList(_ list: [Any?]) -> $className? ');
 
     indent.addScoped('{', '}', () {
-      enumerate(getFieldsInSerializationOrder(klass),
+      enumerate(getFieldsInSerializationOrder(classDefinition),
           (int index, final NamedType field) {
         final String listValue = 'list[$index]';
 
         _writeDecodeCasting(
-          root: root,
           indent: indent,
           value: listValue,
           variableName: field.name,
           type: field.type,
-          listEncodedClassNames: customClassNames,
-          listEncodedEnumNames: customEnumNames,
         );
       });
 
       indent.newln();
       indent.write('return ');
       indent.addScoped('$className(', ')', () {
-        for (final NamedType field in getFieldsInSerializationOrder(klass)) {
+        for (final NamedType field
+            in getFieldsInSerializationOrder(classDefinition)) {
           final String comma =
-              getFieldsInSerializationOrder(klass).last == field ? '' : ',';
+              getFieldsInSerializationOrder(classDefinition).last == field
+                  ? ''
+                  : ',';
           indent.writeln('${field.name}: ${field.name}$comma');
         }
       });
@@ -280,7 +265,7 @@ import FlutterMacOS
     String getEnumSafeArgumentExpression(
         Root root, int count, NamedType argument) {
       String enumTag = '';
-      if (isEnum(root, argument.type)) {
+      if (argument.type.isEnum) {
         enumTag = argument.type.isNullable ? '?.rawValue' : '.rawValue';
       }
 
@@ -326,12 +311,12 @@ import FlutterMacOS
         addDocumentationComments(
             indent, func.documentationComments, _docCommentSpec);
         indent.writeScoped('${_getMethodSignature(func)} {', '}', () {
-          final Iterable<String> enumSafeArgNames = func.arguments
+          final Iterable<String> enumSafeArgNames = func.parameters
               .asMap()
               .entries
               .map((MapEntry<int, NamedType> e) =>
                   getEnumSafeArgumentExpression(root, e.key, e.value));
-          final String sendArgument = func.arguments.isEmpty
+          final String sendArgument = func.parameters.isEmpty
               ? 'nil'
               : '[${enumSafeArgNames.join(', ')}] as [Any?]';
           const String channel = 'channel';
@@ -367,13 +352,15 @@ import FlutterMacOS
               if (func.returnType.isVoid) {
                 indent.writeln('completion(.success(Void()))');
               } else {
-                _writeDecodeCasting(
-                  root: root,
-                  indent: indent,
-                  value: 'listResponse[0]',
-                  variableName: 'result',
-                  type: func.returnType,
-                );
+                final String fieldType = _swiftTypeForDartType(func.returnType);
+
+                _writeGenericCasting(
+                    indent: indent,
+                    value: 'listResponse[0]',
+                    variableName: 'result',
+                    fieldType: fieldType,
+                    type: func.returnType);
+
                 indent.writeln('completion(.success(result))');
               }
             });
@@ -481,7 +468,7 @@ import FlutterMacOS
           indent.addScoped('{', '}', () {
             indent.write('$varChannelName.setMessageHandler ');
             final String messageVarName =
-                method.arguments.isNotEmpty ? 'message' : '_';
+                method.parameters.isNotEmpty ? 'message' : '_';
             indent.addScoped('{ $messageVarName, reply in', '}', () {
               final List<String> methodArgument = <String>[];
               if (components.arguments.isNotEmpty) {
@@ -491,13 +478,15 @@ import FlutterMacOS
                   final String argName =
                       _getSafeArgumentName(index, arg.namedType);
                   final String argIndex = 'args[$index]';
-                  _writeDecodeCasting(
-                    root: root,
-                    indent: indent,
-                    value: argIndex,
-                    variableName: argName,
-                    type: arg.type,
-                  );
+                  final String fieldType = _swiftTypeForDartType(arg.type);
+
+                  _writeGenericCasting(
+                      indent: indent,
+                      value: argIndex,
+                      variableName: argName,
+                      fieldType: fieldType,
+                      type: arg.type);
+
                   if (arg.label == '_') {
                     methodArgument.add(argName);
                   } else {
@@ -520,9 +509,8 @@ import FlutterMacOS
                   indent.addScoped('{', '}', () {
                     final String nullsafe =
                         method.returnType.isNullable ? '?' : '';
-                    final String enumTag = isEnum(root, method.returnType)
-                        ? '$nullsafe.rawValue'
-                        : '';
+                    final String enumTag =
+                        method.returnType.isEnum ? '$nullsafe.rawValue' : '';
                     indent.writeln('case .success$successVariableInit:');
                     indent.nest(1, () {
                       indent.writeln('reply(wrapResult($resultName$enumTag))');
@@ -541,13 +529,13 @@ import FlutterMacOS
                     indent.writeln('reply(wrapResult(nil))');
                   } else {
                     String enumTag = '';
-                    if (isEnum(root, method.returnType)) {
+                    if (method.returnType.isEnum) {
                       enumTag = '.rawValue';
                     }
-                    enumTag = method.returnType.isNullable &&
-                            isEnum(root, method.returnType)
-                        ? '?$enumTag'
-                        : enumTag;
+                    enumTag =
+                        method.returnType.isNullable && method.returnType.isEnum
+                            ? '?$enumTag'
+                            : enumTag;
                     indent.writeln('let result = $call');
                     indent.writeln('reply(wrapResult(result$enumTag))');
                   }
@@ -654,49 +642,60 @@ import FlutterMacOS
     indent.newln();
   }
 
+  String _castForceUnwrap(String value, TypeDeclaration type) {
+    assert(!type.isVoid);
+    if (type.isEnum) {
+      String output =
+          '${_swiftTypeForDartType(type)}(rawValue: $value as! Int)!';
+      if (type.isNullable) {
+        output = 'isNullish($value) ? nil : $output';
+      }
+      return output;
+    } else if (type.baseName == 'Object') {
+      return value + (type.isNullable ? '' : '!');
+    } else if (type.baseName == 'int') {
+      if (type.isNullable) {
+        // Nullable ints need to check for NSNull, and Int32 before casting can be done safely.
+        // This nested ternary is a necessary evil to avoid less efficient conversions.
+        return 'isNullish($value) ? nil : ($value is Int64? ? $value as! Int64? : Int64($value as! Int32))';
+      } else {
+        return '$value is Int64 ? $value as! Int64 : Int64($value as! Int32)';
+      }
+    } else if (type.isNullable) {
+      return 'nilOrValue($value)';
+    } else {
+      return '$value as! ${_swiftTypeForDartType(type)}';
+    }
+  }
+
+  void _writeGenericCasting({
+    required Indent indent,
+    required String value,
+    required String variableName,
+    required String fieldType,
+    required TypeDeclaration type,
+  }) {
+    if (type.isNullable) {
+      indent.writeln(
+          'let $variableName: $fieldType? = ${_castForceUnwrap(value, type)}');
+    } else {
+      indent.writeln('let $variableName = ${_castForceUnwrap(value, type)}');
+    }
+  }
+
   /// Writes decode and casting code for any type.
   ///
   /// Optional parameters should only be used for class decoding.
   void _writeDecodeCasting({
-    required Root root,
     required Indent indent,
     required String value,
     required String variableName,
     required TypeDeclaration type,
-    Set<String>? listEncodedClassNames,
-    Set<String>? listEncodedEnumNames,
   }) {
-    String castForceUnwrap(String value, TypeDeclaration type, Root root) {
-      assert(!type.isVoid);
-      if (isEnum(root, type)) {
-        String output =
-            '${_swiftTypeForDartType(type)}(rawValue: $value as! Int)!';
-        if (type.isNullable) {
-          output = 'isNullish($value) ? nil : $output';
-        }
-        return output;
-      } else if (type.baseName == 'Object') {
-        return value + (type.isNullable ? '' : '!');
-      } else if (type.baseName == 'int') {
-        if (type.isNullable) {
-          // Nullable ints need to check for NSNull, and Int32 before casting can be done safely.
-          // This nested ternary is a necessary evil to avoid less efficient conversions.
-          return 'isNullish($value) ? nil : ($value is Int64? ? $value as! Int64? : Int64($value as! Int32))';
-        } else {
-          return '$value is Int64 ? $value as! Int64 : Int64($value as! Int32)';
-        }
-      } else if (type.isNullable) {
-        return 'nilOrValue($value)';
-      } else {
-        return '$value as! ${_swiftTypeForDartType(type)}';
-      }
-    }
-
     final String fieldType = _swiftTypeForDartType(type);
 
     if (type.isNullable) {
-      if (listEncodedClassNames != null &&
-          listEncodedClassNames.contains(type.baseName)) {
+      if (type.isClass) {
         indent.writeln('var $variableName: $fieldType? = nil');
         indent
             .write('if let ${variableName}List: [Any?] = nilOrValue($value) ');
@@ -704,11 +703,10 @@ import FlutterMacOS
           indent.writeln(
               '$variableName = $fieldType.fromList(${variableName}List)');
         });
-      } else if (listEncodedEnumNames != null &&
-          listEncodedEnumNames.contains(type.baseName)) {
+      } else if (type.isEnum) {
         indent.writeln('var $variableName: $fieldType? = nil');
         indent.writeln(
-            'let ${variableName}EnumVal: Int? = ${castForceUnwrap(value, const TypeDeclaration(baseName: 'Int', isNullable: true), root)}');
+            'let ${variableName}EnumVal: Int? = ${_castForceUnwrap(value, const TypeDeclaration(baseName: 'Int', isNullable: true))}');
         indent
             .write('if let ${variableName}RawValue = ${variableName}EnumVal ');
         indent.addScoped('{', '}', () {
@@ -716,17 +714,26 @@ import FlutterMacOS
               '$variableName = $fieldType(rawValue: ${variableName}RawValue)!');
         });
       } else {
-        indent.writeln(
-            'let $variableName: $fieldType? = ${castForceUnwrap(value, type, root)}');
+        _writeGenericCasting(
+          indent: indent,
+          value: value,
+          variableName: variableName,
+          fieldType: fieldType,
+          type: type,
+        );
       }
     } else {
-      if (listEncodedClassNames != null &&
-          listEncodedClassNames.contains(type.baseName)) {
+      if (type.isClass) {
         indent.writeln(
             'let $variableName = $fieldType.fromList($value as! [Any?])!');
       } else {
-        indent.writeln(
-            'let $variableName = ${castForceUnwrap(value, type, root)}');
+        _writeGenericCasting(
+          indent: indent,
+          value: value,
+          variableName: variableName,
+          fieldType: fieldType,
+          type: type,
+        );
       }
     }
   }
@@ -812,11 +819,6 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
   }
 }
 
-HostDatatype _getHostDatatype(Root root, NamedType field) {
-  return getFieldHostDatatype(field, root.classes, root.enums,
-      (TypeDeclaration x) => _swiftTypeForBuiltinDartType(x));
-}
-
 /// Calculates the name of the codec that will be generated for [api].
 String _getCodecName(Api api) => '${api.name}Codec';
 
@@ -899,17 +901,17 @@ String _getMethodSignature(Method func) {
       ? 'Void'
       : _nullsafeSwiftTypeForDartType(func.returnType);
 
-  if (func.arguments.isEmpty) {
+  if (func.parameters.isEmpty) {
     return 'func ${func.name}(completion: @escaping (Result<$returnType, FlutterError>) -> Void)';
   } else {
-    final Iterable<String> argTypes = func.arguments
+    final Iterable<String> argTypes = func.parameters
         .map((NamedType e) => _nullsafeSwiftTypeForDartType(e.type));
     final Iterable<String> argLabels = indexMap(components.arguments,
         (int index, _SwiftFunctionArgument argument) {
       return argument.label ?? _getArgumentName(index, argument.namedType);
     });
     final Iterable<String> argNames =
-        indexMap(func.arguments, _getSafeArgumentName);
+        indexMap(func.parameters, _getSafeArgumentName);
     final String argsSignature = map3(argTypes, argLabels, argNames,
             (String type, String label, String name) => '$label $name: $type')
         .join(', ');
@@ -957,7 +959,7 @@ class _SwiftFunctionComponents {
       return _SwiftFunctionComponents._(
         name: method.name,
         returnType: method.returnType,
-        arguments: method.arguments
+        arguments: method.parameters
             .map((NamedType field) => _SwiftFunctionArgument(
                   name: field.name,
                   type: field.type,
@@ -969,20 +971,20 @@ class _SwiftFunctionComponents {
     }
 
     final String argsExtractor =
-        repeat(r'(\w+):', method.arguments.length).join();
+        repeat(r'(\w+):', method.parameters.length).join();
     final RegExp signatureRegex = RegExp(r'(\w+) *\(' + argsExtractor + r'\)');
     final RegExpMatch match = signatureRegex.firstMatch(method.swiftFunction)!;
 
     final Iterable<String> labels = match
         .groups(List<int>.generate(
-            method.arguments.length, (int index) => index + 2))
+            method.parameters.length, (int index) => index + 2))
         .whereType();
 
     return _SwiftFunctionComponents._(
       name: match.group(1)!,
       returnType: method.returnType,
       arguments: map2(
-        method.arguments,
+        method.parameters,
         labels,
         (NamedType field, String label) => _SwiftFunctionArgument(
           name: field.name,
diff --git a/packages/pigeon/pigeons/core_tests.dart b/packages/pigeon/pigeons/core_tests.dart
index 2f5ef13732b..a0c6a3ccf29 100644
--- a/packages/pigeon/pigeons/core_tests.dart
+++ b/packages/pigeon/pigeons/core_tests.dart
@@ -171,6 +171,21 @@ abstract class HostIntegrationCoreApi {
   @SwiftFunction('echo(_:)')
   AnEnum echoEnum(AnEnum anEnum);
 
+  /// Returns the default string.
+  @ObjCSelector('echoNamedDefaultString:')
+  @SwiftFunction('echoNamedDefault(_:)')
+  String echoNamedDefaultString({String aString = 'default'});
+
+  /// Returns passed in double.
+  @ObjCSelector('echoOptionalDefaultDouble:')
+  @SwiftFunction('echoOptionalDefault(_:)')
+  double echoOptionalDefaultDouble([double aDouble = 3.14]);
+
+  /// Returns passed in int.
+  @ObjCSelector('echoRequiredInt:')
+  @SwiftFunction('echoRequired(_:)')
+  int echoRequiredInt({required int anInt});
+
   // ========== Synchronous nullable method tests ==========
 
   /// Returns the passed object, to test serialization and deserialization.
@@ -240,6 +255,16 @@ abstract class HostIntegrationCoreApi {
   @SwiftFunction('echoNullable(_:)')
   AnEnum? echoNullableEnum(AnEnum? anEnum);
 
+  /// Returns passed in int.
+  @ObjCSelector('echoOptionalNullableInt:')
+  @SwiftFunction('echoOptional(_:)')
+  int? echoOptionalNullableInt([int? aNullableInt]);
+
+  /// Returns the passed in string.
+  @ObjCSelector('echoNamedNullableString:')
+  @SwiftFunction('echoNamed(_:)')
+  String? echoNamedNullableString({String? aNullableString});
+
   // ========== Asynchronous method tests ==========
 
   /// A no-op function taking no arguments and returning no value, to sanity
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/AlternateLanguageTestPlugin.java b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/AlternateLanguageTestPlugin.java
index 694bbcaff9c..21037c5e99c 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/AlternateLanguageTestPlugin.java
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/AlternateLanguageTestPlugin.java
@@ -111,6 +111,21 @@ public void throwErrorFromVoid() {
     return anEnum;
   }
 
+  @Override
+  public @NonNull String echoNamedDefaultString(@NonNull String aString) {
+    return aString;
+  }
+
+  @Override
+  public @NonNull Double echoOptionalDefaultDouble(@NonNull Double aDouble) {
+    return aDouble;
+  }
+
+  @Override
+  public @NonNull Long echoRequiredInt(@NonNull Long anInt) {
+    return anInt;
+  }
+
   @Override
   public @Nullable String extractNestedNullableString(@NonNull AllClassesWrapper wrapper) {
     return wrapper.getAllNullableTypes().getANullableString();
@@ -182,6 +197,16 @@ public void throwErrorFromVoid() {
     return anEnum;
   }
 
+  @Override
+  public @Nullable Long echoOptionalNullableInt(@Nullable Long aNullableInt) {
+    return aNullableInt;
+  }
+
+  @Override
+  public @Nullable String echoNamedNullableString(@Nullable String aNullableString) {
+    return aNullableString;
+  }
+
   @Override
   public void noopAsync(@NonNull Result<Void> result) {
     result.success(null);
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
index e508232de4c..60586828274 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
@@ -1033,6 +1033,15 @@ public interface HostIntegrationCoreApi {
     /** Returns the passed enum to test serialization and deserialization. */
     @NonNull
     AnEnum echoEnum(@NonNull AnEnum anEnum);
+    /** Returns the default string. */
+    @NonNull
+    String echoNamedDefaultString(@NonNull String aString);
+    /** Returns passed in double. */
+    @NonNull
+    Double echoOptionalDefaultDouble(@NonNull Double aDouble);
+    /** Returns passed in int. */
+    @NonNull
+    Long echoRequiredInt(@NonNull Long anInt);
     /** Returns the passed object, to test serialization and deserialization. */
     @Nullable
     AllNullableTypes echoAllNullableTypes(@Nullable AllNullableTypes everything);
@@ -1079,6 +1088,12 @@ AllNullableTypes sendMultipleNullableTypes(
 
     @Nullable
     AnEnum echoNullableEnum(@Nullable AnEnum anEnum);
+    /** Returns passed in int. */
+    @Nullable
+    Long echoOptionalNullableInt(@Nullable Long aNullableInt);
+    /** Returns the passed in string. */
+    @Nullable
+    String echoNamedNullableString(@Nullable String aNullableString);
     /**
      * A no-op function taking no arguments and returning no value, to sanity test basic
      * asynchronous calling.
@@ -1570,6 +1585,82 @@ static void setUp(
           channel.setMessageHandler(null);
         }
       }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedDefaultString",
+                getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                String aStringArg = (String) args.get(0);
+                try {
+                  String output = api.echoNamedDefaultString(aStringArg);
+                  wrapped.add(0, output);
+                } catch (Throwable exception) {
+                  ArrayList<Object> wrappedError = wrapError(exception);
+                  wrapped = wrappedError;
+                }
+                reply.reply(wrapped);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalDefaultDouble",
+                getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                Double aDoubleArg = (Double) args.get(0);
+                try {
+                  Double output = api.echoOptionalDefaultDouble(aDoubleArg);
+                  wrapped.add(0, output);
+                } catch (Throwable exception) {
+                  ArrayList<Object> wrappedError = wrapError(exception);
+                  wrapped = wrappedError;
+                }
+                reply.reply(wrapped);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoRequiredInt",
+                getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                Number anIntArg = (Number) args.get(0);
+                try {
+                  Long output =
+                      api.echoRequiredInt((anIntArg == null) ? null : anIntArg.longValue());
+                  wrapped.add(0, output);
+                } catch (Throwable exception) {
+                  ArrayList<Object> wrappedError = wrapError(exception);
+                  wrapped = wrappedError;
+                }
+                reply.reply(wrapped);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
       {
         BasicMessageChannel<Object> channel =
             new BasicMessageChannel<>(
@@ -1903,6 +1994,58 @@ static void setUp(
           channel.setMessageHandler(null);
         }
       }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalNullableInt",
+                getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                Number aNullableIntArg = (Number) args.get(0);
+                try {
+                  Long output =
+                      api.echoOptionalNullableInt(
+                          (aNullableIntArg == null) ? null : aNullableIntArg.longValue());
+                  wrapped.add(0, output);
+                } catch (Throwable exception) {
+                  ArrayList<Object> wrappedError = wrapError(exception);
+                  wrapped = wrappedError;
+                }
+                reply.reply(wrapped);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedNullableString",
+                getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                String aNullableStringArg = (String) args.get(0);
+                try {
+                  String output = api.echoNamedNullableString(aNullableStringArg);
+                  wrapped.add(0, output);
+                } catch (Throwable exception) {
+                  ArrayList<Object> wrappedError = wrapError(exception);
+                  wrapped = wrappedError;
+                }
+                reply.reply(wrapped);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
       {
         BasicMessageChannel<Object> channel =
             new BasicMessageChannel<>(
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/AlternateLanguageTestPlugin.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/AlternateLanguageTestPlugin.m
index d24bd629ba3..d1e42a10cca 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/AlternateLanguageTestPlugin.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/AlternateLanguageTestPlugin.m
@@ -95,6 +95,21 @@ - (AnEnumBox *_Nullable)echoEnum:(AnEnum)anEnum error:(FlutterError *_Nullable *
   return [[AnEnumBox alloc] initWithValue:anEnum];
 }
 
+- (nullable NSString *)echoNamedDefaultString:(NSString *)aString
+                                        error:(FlutterError *_Nullable *_Nonnull)error {
+  return aString;
+}
+
+- (nullable NSNumber *)echoOptionalDefaultDouble:(double)aDouble
+                                           error:(FlutterError *_Nullable *_Nonnull)error {
+  return @(aDouble);
+}
+
+- (nullable NSNumber *)echoRequiredInt:(NSInteger)anInt
+                                 error:(FlutterError *_Nullable *_Nonnull)error {
+  return @(anInt);
+}
+
 - (nullable NSString *)extractNestedNullableStringFrom:(AllClassesWrapper *)wrapper
                                                  error:(FlutterError *_Nullable *_Nonnull)error {
   return wrapper.allNullableTypes.aNullableString;
@@ -167,6 +182,16 @@ - (AnEnumBox *_Nullable)echoNullableEnum:(nullable AnEnumBox *)AnEnumBoxed
   return AnEnumBoxed;
 }
 
+- (nullable NSNumber *)echoOptionalNullableInt:(nullable NSNumber *)aNullableInt
+                                         error:(FlutterError *_Nullable *_Nonnull)error {
+  return aNullableInt;
+}
+
+- (nullable NSString *)echoNamedNullableString:(nullable NSString *)aNullableString
+                                         error:(FlutterError *_Nullable *_Nonnull)error {
+  return aNullableString;
+}
+
 - (void)noopAsyncWithCompletion:(void (^)(FlutterError *_Nullable))completion {
   completion(nil);
 }
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h
index 36ead686fc2..782c3794a13 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.h
@@ -186,6 +186,21 @@ NSObject<FlutterMessageCodec> *HostIntegrationCoreApiGetCodec(void);
 ///
 /// @return `nil` only when `error != nil`.
 - (AnEnumBox *_Nullable)echoEnum:(AnEnum)anEnum error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns the default string.
+///
+/// @return `nil` only when `error != nil`.
+- (nullable NSString *)echoNamedDefaultString:(NSString *)aString
+                                        error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns passed in double.
+///
+/// @return `nil` only when `error != nil`.
+- (nullable NSNumber *)echoOptionalDefaultDouble:(double)aDouble
+                                           error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns passed in int.
+///
+/// @return `nil` only when `error != nil`.
+- (nullable NSNumber *)echoRequiredInt:(NSInteger)anInt
+                                 error:(FlutterError *_Nullable *_Nonnull)error;
 /// Returns the passed object, to test serialization and deserialization.
 - (nullable AllNullableTypes *)echoAllNullableTypes:(nullable AllNullableTypes *)everything
                                               error:(FlutterError *_Nullable *_Nonnull)error;
@@ -236,6 +251,12 @@ NSObject<FlutterMessageCodec> *HostIntegrationCoreApiGetCodec(void);
                                                      error:(FlutterError *_Nullable *_Nonnull)error;
 - (AnEnumBox *_Nullable)echoNullableEnum:(nullable AnEnumBox *)anEnumBoxed
                                    error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns passed in int.
+- (nullable NSNumber *)echoOptionalNullableInt:(nullable NSNumber *)aNullableInt
+                                         error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns the passed in string.
+- (nullable NSString *)echoNamedNullableString:(nullable NSString *)aNullableString
+                                         error:(FlutterError *_Nullable *_Nonnull)error;
 /// A no-op function taking no arguments and returning no value, to sanity
 /// test basic asynchronous calling.
 - (void)noopAsyncWithCompletion:(void (^)(FlutterError *_Nullable))completion;
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m
index 99bf5a54d13..0cc5b059c04 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/ios/Classes/CoreTests.gen.m
@@ -672,6 +672,75 @@ void SetUpHostIntegrationCoreApi(id<FlutterBinaryMessenger> binaryMessenger,
       [channel setMessageHandler:nil];
     }
   }
+  /// Returns the default string.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoNamedDefaultString"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoNamedDefaultString:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoNamedDefaultString:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
+        FlutterError *error;
+        NSString *output = [api echoNamedDefaultString:arg_aString error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
+  /// Returns passed in double.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoOptionalDefaultDouble"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoOptionalDefaultDouble:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoOptionalDefaultDouble:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
+        FlutterError *error;
+        NSNumber *output = [api echoOptionalDefaultDouble:arg_aDouble error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
+  /// Returns passed in int.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:
+               @"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoRequiredInt"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert(
+          [api respondsToSelector:@selector(echoRequiredInt:error:)],
+          @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoRequiredInt:error:)",
+          api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
+        FlutterError *error;
+        NSNumber *output = [api echoRequiredInt:arg_anInt error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
   /// Returns the passed object, to test serialization and deserialization.
   {
     FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
@@ -985,6 +1054,52 @@ void SetUpHostIntegrationCoreApi(id<FlutterBinaryMessenger> binaryMessenger,
       [channel setMessageHandler:nil];
     }
   }
+  /// Returns passed in int.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoOptionalNullableInt"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoOptionalNullableInt:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoOptionalNullableInt:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 0);
+        FlutterError *error;
+        NSNumber *output = [api echoOptionalNullableInt:arg_aNullableInt error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
+  /// Returns the passed in string.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoNamedNullableString"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoNamedNullableString:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoNamedNullableString:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 0);
+        FlutterError *error;
+        NSString *output = [api echoNamedNullableString:arg_aNullableString error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic asynchronous calling.
   {
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/AlternateLanguageTestPlugin.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/AlternateLanguageTestPlugin.m
index 6c37758ccae..e9d679f4215 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/AlternateLanguageTestPlugin.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/AlternateLanguageTestPlugin.m
@@ -94,6 +94,20 @@ - (nullable AllClassesWrapper *)echoClassWrapper:(AllClassesWrapper *)wrapper
 - (AnEnumBox *_Nullable)echoEnum:(AnEnum)anEnum error:(FlutterError *_Nullable *_Nonnull)error {
   return [[AnEnumBox alloc] initWithValue:anEnum];
 }
+- (nullable NSString *)echoNamedDefaultString:(NSString *)aString
+                                        error:(FlutterError *_Nullable *_Nonnull)error {
+  return aString;
+}
+
+- (nullable NSNumber *)echoOptionalDefaultDouble:(double)aDouble
+                                           error:(FlutterError *_Nullable *_Nonnull)error {
+  return @(aDouble);
+}
+
+- (nullable NSNumber *)echoRequiredInt:(NSInteger)anInt
+                                 error:(FlutterError *_Nullable *_Nonnull)error {
+  return @(anInt);
+}
 
 - (nullable NSString *)extractNestedNullableStringFrom:(AllClassesWrapper *)wrapper
                                                  error:(FlutterError *_Nullable *_Nonnull)error {
@@ -167,6 +181,16 @@ - (AnEnumBox *_Nullable)echoNullableEnum:(nullable AnEnumBox *)AnEnumBoxed
   return AnEnumBoxed;
 }
 
+- (nullable NSNumber *)echoOptionalNullableInt:(nullable NSNumber *)aNullableInt
+                                         error:(FlutterError *_Nullable *_Nonnull)error {
+  return aNullableInt;
+}
+
+- (nullable NSString *)echoNamedNullableString:(nullable NSString *)aNullableString
+                                         error:(FlutterError *_Nullable *_Nonnull)error {
+  return aNullableString;
+}
+
 - (void)noopAsyncWithCompletion:(void (^)(FlutterError *_Nullable))completion {
   completion(nil);
 }
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h
index 36ead686fc2..782c3794a13 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.h
@@ -186,6 +186,21 @@ NSObject<FlutterMessageCodec> *HostIntegrationCoreApiGetCodec(void);
 ///
 /// @return `nil` only when `error != nil`.
 - (AnEnumBox *_Nullable)echoEnum:(AnEnum)anEnum error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns the default string.
+///
+/// @return `nil` only when `error != nil`.
+- (nullable NSString *)echoNamedDefaultString:(NSString *)aString
+                                        error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns passed in double.
+///
+/// @return `nil` only when `error != nil`.
+- (nullable NSNumber *)echoOptionalDefaultDouble:(double)aDouble
+                                           error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns passed in int.
+///
+/// @return `nil` only when `error != nil`.
+- (nullable NSNumber *)echoRequiredInt:(NSInteger)anInt
+                                 error:(FlutterError *_Nullable *_Nonnull)error;
 /// Returns the passed object, to test serialization and deserialization.
 - (nullable AllNullableTypes *)echoAllNullableTypes:(nullable AllNullableTypes *)everything
                                               error:(FlutterError *_Nullable *_Nonnull)error;
@@ -236,6 +251,12 @@ NSObject<FlutterMessageCodec> *HostIntegrationCoreApiGetCodec(void);
                                                      error:(FlutterError *_Nullable *_Nonnull)error;
 - (AnEnumBox *_Nullable)echoNullableEnum:(nullable AnEnumBox *)anEnumBoxed
                                    error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns passed in int.
+- (nullable NSNumber *)echoOptionalNullableInt:(nullable NSNumber *)aNullableInt
+                                         error:(FlutterError *_Nullable *_Nonnull)error;
+/// Returns the passed in string.
+- (nullable NSString *)echoNamedNullableString:(nullable NSString *)aNullableString
+                                         error:(FlutterError *_Nullable *_Nonnull)error;
 /// A no-op function taking no arguments and returning no value, to sanity
 /// test basic asynchronous calling.
 - (void)noopAsyncWithCompletion:(void (^)(FlutterError *_Nullable))completion;
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m
index 99bf5a54d13..0cc5b059c04 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/macos/Classes/CoreTests.gen.m
@@ -672,6 +672,75 @@ void SetUpHostIntegrationCoreApi(id<FlutterBinaryMessenger> binaryMessenger,
       [channel setMessageHandler:nil];
     }
   }
+  /// Returns the default string.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoNamedDefaultString"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoNamedDefaultString:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoNamedDefaultString:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSString *arg_aString = GetNullableObjectAtIndex(args, 0);
+        FlutterError *error;
+        NSString *output = [api echoNamedDefaultString:arg_aString error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
+  /// Returns passed in double.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoOptionalDefaultDouble"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoOptionalDefaultDouble:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoOptionalDefaultDouble:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        double arg_aDouble = [GetNullableObjectAtIndex(args, 0) doubleValue];
+        FlutterError *error;
+        NSNumber *output = [api echoOptionalDefaultDouble:arg_aDouble error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
+  /// Returns passed in int.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:
+               @"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoRequiredInt"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert(
+          [api respondsToSelector:@selector(echoRequiredInt:error:)],
+          @"HostIntegrationCoreApi api (%@) doesn't respond to @selector(echoRequiredInt:error:)",
+          api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSInteger arg_anInt = [GetNullableObjectAtIndex(args, 0) integerValue];
+        FlutterError *error;
+        NSNumber *output = [api echoRequiredInt:arg_anInt error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
   /// Returns the passed object, to test serialization and deserialization.
   {
     FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
@@ -985,6 +1054,52 @@ void SetUpHostIntegrationCoreApi(id<FlutterBinaryMessenger> binaryMessenger,
       [channel setMessageHandler:nil];
     }
   }
+  /// Returns passed in int.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoOptionalNullableInt"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoOptionalNullableInt:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoOptionalNullableInt:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSNumber *arg_aNullableInt = GetNullableObjectAtIndex(args, 0);
+        FlutterError *error;
+        NSNumber *output = [api echoOptionalNullableInt:arg_aNullableInt error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
+  /// Returns the passed in string.
+  {
+    FlutterBasicMessageChannel *channel = [[FlutterBasicMessageChannel alloc]
+           initWithName:@"dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+                        @"echoNamedNullableString"
+        binaryMessenger:binaryMessenger
+                  codec:HostIntegrationCoreApiGetCodec()];
+    if (api) {
+      NSCAssert([api respondsToSelector:@selector(echoNamedNullableString:error:)],
+                @"HostIntegrationCoreApi api (%@) doesn't respond to "
+                @"@selector(echoNamedNullableString:error:)",
+                api);
+      [channel setMessageHandler:^(id _Nullable message, FlutterReply callback) {
+        NSArray *args = message;
+        NSString *arg_aNullableString = GetNullableObjectAtIndex(args, 0);
+        FlutterError *error;
+        NSString *output = [api echoNamedNullableString:arg_aNullableString error:&error];
+        callback(wrapResult(output, error));
+      }];
+    } else {
+      [channel setMessageHandler:nil];
+    }
+  }
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic asynchronous calling.
   {
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
index 9daa7c9317f..6b60a87e146 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
@@ -139,7 +139,7 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
       'e': null
     },
     anEnum: AnEnum.two,
-    anObject: 0,
+    anObject: 1,
   );
 
   final AllNullableTypes genericAllNullableTypes = AllNullableTypes(
@@ -337,7 +337,6 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     testWidgets('Int serialize and deserialize correctly',
         (WidgetTester _) async {
       final HostIntegrationCoreApi api = HostIntegrationCoreApi();
-
       const int sentInt = _regularInt;
       final int receivedInt = await api.echoInt(sentInt);
       expect(receivedInt, sentInt);
@@ -374,7 +373,7 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     testWidgets('strings serialize and deserialize correctly',
         (WidgetTester _) async {
       final HostIntegrationCoreApi api = HostIntegrationCoreApi();
-      const String sentString = "I'm a computer";
+      const String sentString = 'default';
       final String receivedString = await api.echoString(sentString);
       expect(receivedString, sentString);
     });
@@ -444,6 +443,49 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
       expect(receivedEnum, sentEnum);
     });
 
+    testWidgets('required named parameter', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+      // This number corresponds with the default value of this method.
+      const int sentInt = _regularInt;
+      final int receivedInt = await api.echoRequiredInt(anInt: sentInt);
+      expect(receivedInt, sentInt);
+    });
+
+    testWidgets('optional default parameter no arg', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+
+      // This number corresponds with the default value of this method.
+      const double sentDouble = 3.14;
+      final double receivedDouble = await api.echoOptionalDefaultDouble();
+      expect(receivedDouble, sentDouble);
+    });
+
+    testWidgets('optional default parameter with arg', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+
+      const double sentDouble = 3.15;
+      final double receivedDouble =
+          await api.echoOptionalDefaultDouble(sentDouble);
+      expect(receivedDouble, sentDouble);
+    });
+
+    testWidgets('named default parameter no arg', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+      // This string corresponds with the default value of this method.
+      const String sentString = 'default';
+      final String receivedString = await api.echoNamedDefaultString();
+      expect(receivedString, sentString);
+    });
+
+    testWidgets('named default parameter with arg', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+      // This string corresponds with the default value of this method.
+      const String sentString = 'notDefault';
+      final String receivedString =
+          await api.echoNamedDefaultString(aString: sentString);
+      expect(receivedString, sentString);
+    });
+
     testWidgets('Nullable Int serialize and deserialize correctly',
         (WidgetTester _) async {
       final HostIntegrationCoreApi api = HostIntegrationCoreApi();
@@ -630,6 +672,36 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
       final AnEnum? echoEnum = await api.echoNullableEnum(sentEnum);
       expect(echoEnum, sentEnum);
     });
+
+    testWidgets('optional nullable parameter', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+
+      const int sentInt = _regularInt;
+      final int? receivedInt = await api.echoOptionalNullableInt(sentInt);
+      expect(receivedInt, sentInt);
+    });
+
+    testWidgets('Null optional nullable parameter', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+
+      final int? receivedNullInt = await api.echoOptionalNullableInt();
+      expect(receivedNullInt, null);
+    });
+
+    testWidgets('named nullable parameter', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+      const String sentString = "I'm a computer";
+      final String? receivedString =
+          await api.echoNamedNullableString(aNullableString: sentString);
+      expect(receivedString, sentString);
+    });
+
+    testWidgets('Null named nullable parameter', (WidgetTester _) async {
+      final HostIntegrationCoreApi api = HostIntegrationCoreApi();
+
+      final String? receivedNullString = await api.echoNamedNullableString();
+      expect(receivedNullString, null);
+    });
   });
 
   group('Host async API tests', () {
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
index e48af86c9af..7222e263b32 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -24,36 +24,38 @@ class BackgroundApi2Host {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   BackgroundApi2Host({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
-  Future<int> add(int arg_x, int arg_y) async {
-    const String channelName =
+  Future<int> add(int x, int y) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.BackgroundApi2Host.add';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_x, arg_y]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[x, y]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 }
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
index 64b721bc2ee..6815f461c94 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -39,19 +39,19 @@ enum AnEnum {
 /// A class containing all supported types.
 class AllTypes {
   AllTypes({
-    required this.aBool,
-    required this.anInt,
-    required this.anInt64,
-    required this.aDouble,
+    this.aBool = false,
+    this.anInt = 0,
+    this.anInt64 = 0,
+    this.aDouble = 0,
     required this.aByteArray,
     required this.a4ByteArray,
     required this.a8ByteArray,
     required this.aFloatArray,
-    required this.aList,
-    required this.aMap,
-    required this.anEnum,
-    required this.aString,
-    required this.anObject,
+    this.aList = const <Object?>[],
+    this.aMap = const <String?, Object?>{},
+    this.anEnum = AnEnum.one,
+    this.aString = '',
+    this.anObject = 0,
   });
 
   bool aBool;
@@ -318,29 +318,32 @@ class HostIntegrationCoreApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   HostIntegrationCoreApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _HostIntegrationCoreApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _HostIntegrationCoreApiCodec();
 
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic calling.
   Future<void> noop() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.noop';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -348,74 +351,79 @@ class HostIntegrationCoreApi {
   }
 
   /// Returns the passed object, to test serialization and deserialization.
-  Future<AllTypes> echoAllTypes(AllTypes arg_everything) async {
-    const String channelName =
+  Future<AllTypes> echoAllTypes(AllTypes everything) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAllTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_everything]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[everything]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as AllTypes?)!;
+      return (__pigeon_replyList[0] as AllTypes?)!;
     }
   }
 
   /// Returns an error, to test error handling.
   Future<Object?> throwError() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.throwError';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return replyList[0];
+      return __pigeon_replyList[0];
     }
   }
 
   /// Returns an error from a void function, to test error handling.
   Future<void> throwErrorFromVoid() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.throwErrorFromVoid';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -424,669 +432,835 @@ class HostIntegrationCoreApi {
 
   /// Returns a Flutter error, to test error handling.
   Future<Object?> throwFlutterError() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.throwFlutterError';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return replyList[0];
+      return __pigeon_replyList[0];
     }
   }
 
   /// Returns passed in int.
-  Future<int> echoInt(int arg_anInt) async {
-    const String channelName =
+  Future<int> echoInt(int anInt) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anInt]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 
   /// Returns passed in double.
-  Future<double> echoDouble(double arg_aDouble) async {
-    const String channelName =
+  Future<double> echoDouble(double aDouble) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoDouble';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aDouble]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as double?)!;
+      return (__pigeon_replyList[0] as double?)!;
     }
   }
 
   /// Returns the passed in boolean.
-  Future<bool> echoBool(bool arg_aBool) async {
-    const String channelName =
+  Future<bool> echoBool(bool aBool) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoBool';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aBool]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as bool?)!;
+      return (__pigeon_replyList[0] as bool?)!;
     }
   }
 
   /// Returns the passed in string.
-  Future<String> echoString(String arg_aString) async {
-    const String channelName =
+  Future<String> echoString(String aString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as String?)!;
+      return (__pigeon_replyList[0] as String?)!;
     }
   }
 
   /// Returns the passed in Uint8List.
-  Future<Uint8List> echoUint8List(Uint8List arg_aUint8List) async {
-    const String channelName =
+  Future<Uint8List> echoUint8List(Uint8List aUint8List) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoUint8List';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aUint8List]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Uint8List?)!;
+      return (__pigeon_replyList[0] as Uint8List?)!;
     }
   }
 
   /// Returns the passed in generic Object.
-  Future<Object> echoObject(Object arg_anObject) async {
-    const String channelName =
+  Future<Object> echoObject(Object anObject) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoObject';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anObject]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return replyList[0]!;
+      return __pigeon_replyList[0]!;
     }
   }
 
   /// Returns the passed list, to test serialization and deserialization.
-  Future<List<Object?>> echoList(List<Object?> arg_aList) async {
-    const String channelName =
+  Future<List<Object?>> echoList(List<Object?> aList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as List<Object?>?)!.cast<Object?>();
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<Object?>();
     }
   }
 
   /// Returns the passed map, to test serialization and deserialization.
-  Future<Map<String?, Object?>> echoMap(Map<String?, Object?> arg_aMap) async {
-    const String channelName =
+  Future<Map<String?, Object?>> echoMap(Map<String?, Object?> aMap) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aMap]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)!.cast<String?, Object?>();
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, Object?>();
     }
   }
 
   /// Returns the passed map to test nested class serialization and deserialization.
-  Future<AllClassesWrapper> echoClassWrapper(
-      AllClassesWrapper arg_wrapper) async {
-    const String channelName =
+  Future<AllClassesWrapper> echoClassWrapper(AllClassesWrapper wrapper) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoClassWrapper';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_wrapper]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[wrapper]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as AllClassesWrapper?)!;
+      return (__pigeon_replyList[0] as AllClassesWrapper?)!;
     }
   }
 
   /// Returns the passed enum to test serialization and deserialization.
-  Future<AnEnum> echoEnum(AnEnum arg_anEnum) async {
-    const String channelName =
+  Future<AnEnum> echoEnum(AnEnum anEnum) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoEnum';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anEnum.index]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anEnum.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return AnEnum.values[replyList[0]! as int];
+      return AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  /// Returns the default string.
+  Future<String> echoNamedDefaultString({String aString = 'default'}) async {
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedDefaultString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?)!;
+    }
+  }
+
+  /// Returns passed in double.
+  Future<double> echoOptionalDefaultDouble([double aDouble = 3.14]) async {
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalDefaultDouble';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as double?)!;
+    }
+  }
+
+  /// Returns passed in int.
+  Future<int> echoRequiredInt({required int anInt}) async {
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoRequiredInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 
   /// Returns the passed object, to test serialization and deserialization.
   Future<AllNullableTypes?> echoAllNullableTypes(
-      AllNullableTypes? arg_everything) async {
-    const String channelName =
+      AllNullableTypes? everything) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAllNullableTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_everything]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[everything]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as AllNullableTypes?);
+      return (__pigeon_replyList[0] as AllNullableTypes?);
     }
   }
 
   /// Returns the inner `aString` value from the wrapped object, to test
   /// sending of nested objects.
-  Future<String?> extractNestedNullableString(
-      AllClassesWrapper arg_wrapper) async {
-    const String channelName =
+  Future<String?> extractNestedNullableString(AllClassesWrapper wrapper) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.extractNestedNullableString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_wrapper]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[wrapper]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as String?);
+      return (__pigeon_replyList[0] as String?);
     }
   }
 
   /// Returns the inner `aString` value from the wrapped object, to test
   /// sending of nested objects.
   Future<AllClassesWrapper> createNestedNullableString(
-      String? arg_nullableString) async {
-    const String channelName =
+      String? nullableString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.createNestedNullableString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_nullableString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[nullableString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as AllClassesWrapper?)!;
+      return (__pigeon_replyList[0] as AllClassesWrapper?)!;
     }
   }
 
   /// Returns passed in arguments of multiple types.
-  Future<AllNullableTypes> sendMultipleNullableTypes(bool? arg_aNullableBool,
-      int? arg_aNullableInt, String? arg_aNullableString) async {
-    const String channelName =
+  Future<AllNullableTypes> sendMultipleNullableTypes(
+      bool? aNullableBool, int? aNullableInt, String? aNullableString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.sendMultipleNullableTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
-    );
-    final List<Object?>? replyList = await channel.send(
-            <Object?>[arg_aNullableBool, arg_aNullableInt, arg_aNullableString])
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+            .send(<Object?>[aNullableBool, aNullableInt, aNullableString])
         as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as AllNullableTypes?)!;
+      return (__pigeon_replyList[0] as AllNullableTypes?)!;
     }
   }
 
   /// Returns passed in int.
-  Future<int?> echoNullableInt(int? arg_aNullableInt) async {
-    const String channelName =
+  Future<int?> echoNullableInt(int? aNullableInt) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableInt]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aNullableInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as int?);
+      return (__pigeon_replyList[0] as int?);
     }
   }
 
   /// Returns passed in double.
-  Future<double?> echoNullableDouble(double? arg_aNullableDouble) async {
-    const String channelName =
+  Future<double?> echoNullableDouble(double? aNullableDouble) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableDouble';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableDouble]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[aNullableDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as double?);
+      return (__pigeon_replyList[0] as double?);
     }
   }
 
   /// Returns the passed in boolean.
-  Future<bool?> echoNullableBool(bool? arg_aNullableBool) async {
-    const String channelName =
+  Future<bool?> echoNullableBool(bool? aNullableBool) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableBool';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableBool]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aNullableBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as bool?);
+      return (__pigeon_replyList[0] as bool?);
     }
   }
 
   /// Returns the passed in string.
-  Future<String?> echoNullableString(String? arg_aNullableString) async {
-    const String channelName =
+  Future<String?> echoNullableString(String? aNullableString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[aNullableString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as String?);
+      return (__pigeon_replyList[0] as String?);
     }
   }
 
   /// Returns the passed in Uint8List.
   Future<Uint8List?> echoNullableUint8List(
-      Uint8List? arg_aNullableUint8List) async {
-    const String channelName =
+      Uint8List? aNullableUint8List) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableUint8List';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableUint8List]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[aNullableUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as Uint8List?);
+      return (__pigeon_replyList[0] as Uint8List?);
     }
   }
 
   /// Returns the passed in generic Object.
-  Future<Object?> echoNullableObject(Object? arg_aNullableObject) async {
-    const String channelName =
+  Future<Object?> echoNullableObject(Object? aNullableObject) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableObject';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableObject]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[aNullableObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return replyList[0];
+      return __pigeon_replyList[0];
     }
   }
 
   /// Returns the passed list, to test serialization and deserialization.
-  Future<List<Object?>?> echoNullableList(
-      List<Object?>? arg_aNullableList) async {
-    const String channelName =
+  Future<List<Object?>?> echoNullableList(List<Object?>? aNullableList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aNullableList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as List<Object?>?)?.cast<Object?>();
+      return (__pigeon_replyList[0] as List<Object?>?)?.cast<Object?>();
     }
   }
 
   /// Returns the passed map, to test serialization and deserialization.
   Future<Map<String?, Object?>?> echoNullableMap(
-      Map<String?, Object?>? arg_aNullableMap) async {
-    const String channelName =
+      Map<String?, Object?>? aNullableMap) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aNullableMap]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aNullableMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)?.cast<String?, Object?>();
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)
+          ?.cast<String?, Object?>();
     }
   }
 
-  Future<AnEnum?> echoNullableEnum(AnEnum? arg_anEnum) async {
-    const String channelName =
+  Future<AnEnum?> echoNullableEnum(AnEnum? anEnum) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNullableEnum';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anEnum?.index]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anEnum?.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as int?) == null
+      return (__pigeon_replyList[0] as int?) == null
           ? null
-          : AnEnum.values[replyList[0]! as int];
+          : AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  /// Returns passed in int.
+  Future<int?> echoOptionalNullableInt([int? aNullableInt]) async {
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalNullableInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aNullableInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?);
+    }
+  }
+
+  /// Returns the passed in string.
+  Future<String?> echoNamedNullableString({String? aNullableString}) async {
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedNullableString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[aNullableString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?);
     }
   }
 
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic asynchronous calling.
   Future<void> noopAsync() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.noopAsync';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -1094,307 +1268,320 @@ class HostIntegrationCoreApi {
   }
 
   /// Returns passed in int asynchronously.
-  Future<int> echoAsyncInt(int arg_anInt) async {
-    const String channelName =
+  Future<int> echoAsyncInt(int anInt) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anInt]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 
   /// Returns passed in double asynchronously.
-  Future<double> echoAsyncDouble(double arg_aDouble) async {
-    const String channelName =
+  Future<double> echoAsyncDouble(double aDouble) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncDouble';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aDouble]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as double?)!;
+      return (__pigeon_replyList[0] as double?)!;
     }
   }
 
   /// Returns the passed in boolean asynchronously.
-  Future<bool> echoAsyncBool(bool arg_aBool) async {
-    const String channelName =
+  Future<bool> echoAsyncBool(bool aBool) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncBool';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aBool]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as bool?)!;
+      return (__pigeon_replyList[0] as bool?)!;
     }
   }
 
   /// Returns the passed string asynchronously.
-  Future<String> echoAsyncString(String arg_aString) async {
-    const String channelName =
+  Future<String> echoAsyncString(String aString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as String?)!;
+      return (__pigeon_replyList[0] as String?)!;
     }
   }
 
   /// Returns the passed in Uint8List asynchronously.
-  Future<Uint8List> echoAsyncUint8List(Uint8List arg_aUint8List) async {
-    const String channelName =
+  Future<Uint8List> echoAsyncUint8List(Uint8List aUint8List) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncUint8List';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aUint8List]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Uint8List?)!;
+      return (__pigeon_replyList[0] as Uint8List?)!;
     }
   }
 
   /// Returns the passed in generic Object asynchronously.
-  Future<Object> echoAsyncObject(Object arg_anObject) async {
-    const String channelName =
+  Future<Object> echoAsyncObject(Object anObject) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncObject';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anObject]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return replyList[0]!;
+      return __pigeon_replyList[0]!;
     }
   }
 
   /// Returns the passed list, to test asynchronous serialization and deserialization.
-  Future<List<Object?>> echoAsyncList(List<Object?> arg_aList) async {
-    const String channelName =
+  Future<List<Object?>> echoAsyncList(List<Object?> aList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as List<Object?>?)!.cast<Object?>();
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<Object?>();
     }
   }
 
   /// Returns the passed map, to test asynchronous serialization and deserialization.
-  Future<Map<String?, Object?>> echoAsyncMap(
-      Map<String?, Object?> arg_aMap) async {
-    const String channelName =
+  Future<Map<String?, Object?>> echoAsyncMap(Map<String?, Object?> aMap) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aMap]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)!.cast<String?, Object?>();
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, Object?>();
     }
   }
 
   /// Returns the passed enum, to test asynchronous serialization and deserialization.
-  Future<AnEnum> echoAsyncEnum(AnEnum arg_anEnum) async {
-    const String channelName =
+  Future<AnEnum> echoAsyncEnum(AnEnum anEnum) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncEnum';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anEnum.index]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anEnum.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return AnEnum.values[replyList[0]! as int];
+      return AnEnum.values[__pigeon_replyList[0]! as int];
     }
   }
 
   /// Responds with an error from an async function returning a value.
   Future<Object?> throwAsyncError() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.throwAsyncError';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return replyList[0];
+      return __pigeon_replyList[0];
     }
   }
 
   /// Responds with an error from an async void function.
   Future<void> throwAsyncErrorFromVoid() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.throwAsyncErrorFromVoid';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -1403,317 +1590,332 @@ class HostIntegrationCoreApi {
 
   /// Responds with a Flutter error from an async function returning a value.
   Future<Object?> throwAsyncFlutterError() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.throwAsyncFlutterError';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return replyList[0];
+      return __pigeon_replyList[0];
     }
   }
 
   /// Returns the passed object, to test async serialization and deserialization.
-  Future<AllTypes> echoAsyncAllTypes(AllTypes arg_everything) async {
-    const String channelName =
+  Future<AllTypes> echoAsyncAllTypes(AllTypes everything) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncAllTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_everything]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[everything]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as AllTypes?)!;
+      return (__pigeon_replyList[0] as AllTypes?)!;
     }
   }
 
   /// Returns the passed object, to test serialization and deserialization.
   Future<AllNullableTypes?> echoAsyncNullableAllNullableTypes(
-      AllNullableTypes? arg_everything) async {
-    const String channelName =
+      AllNullableTypes? everything) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableAllNullableTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_everything]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[everything]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as AllNullableTypes?);
+      return (__pigeon_replyList[0] as AllNullableTypes?);
     }
   }
 
   /// Returns passed in int asynchronously.
-  Future<int?> echoAsyncNullableInt(int? arg_anInt) async {
-    const String channelName =
+  Future<int?> echoAsyncNullableInt(int? anInt) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anInt]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as int?);
+      return (__pigeon_replyList[0] as int?);
     }
   }
 
   /// Returns passed in double asynchronously.
-  Future<double?> echoAsyncNullableDouble(double? arg_aDouble) async {
-    const String channelName =
+  Future<double?> echoAsyncNullableDouble(double? aDouble) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableDouble';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aDouble]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as double?);
+      return (__pigeon_replyList[0] as double?);
     }
   }
 
   /// Returns the passed in boolean asynchronously.
-  Future<bool?> echoAsyncNullableBool(bool? arg_aBool) async {
-    const String channelName =
+  Future<bool?> echoAsyncNullableBool(bool? aBool) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableBool';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aBool]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as bool?);
+      return (__pigeon_replyList[0] as bool?);
     }
   }
 
   /// Returns the passed string asynchronously.
-  Future<String?> echoAsyncNullableString(String? arg_aString) async {
-    const String channelName =
+  Future<String?> echoAsyncNullableString(String? aString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as String?);
+      return (__pigeon_replyList[0] as String?);
     }
   }
 
   /// Returns the passed in Uint8List asynchronously.
-  Future<Uint8List?> echoAsyncNullableUint8List(
-      Uint8List? arg_aUint8List) async {
-    const String channelName =
+  Future<Uint8List?> echoAsyncNullableUint8List(Uint8List? aUint8List) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableUint8List';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aUint8List]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as Uint8List?);
+      return (__pigeon_replyList[0] as Uint8List?);
     }
   }
 
   /// Returns the passed in generic Object asynchronously.
-  Future<Object?> echoAsyncNullableObject(Object? arg_anObject) async {
-    const String channelName =
+  Future<Object?> echoAsyncNullableObject(Object? anObject) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableObject';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anObject]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return replyList[0];
+      return __pigeon_replyList[0];
     }
   }
 
   /// Returns the passed list, to test asynchronous serialization and deserialization.
-  Future<List<Object?>?> echoAsyncNullableList(List<Object?>? arg_aList) async {
-    const String channelName =
+  Future<List<Object?>?> echoAsyncNullableList(List<Object?>? aList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as List<Object?>?)?.cast<Object?>();
+      return (__pigeon_replyList[0] as List<Object?>?)?.cast<Object?>();
     }
   }
 
   /// Returns the passed map, to test asynchronous serialization and deserialization.
   Future<Map<String?, Object?>?> echoAsyncNullableMap(
-      Map<String?, Object?>? arg_aMap) async {
-    const String channelName =
+      Map<String?, Object?>? aMap) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aMap]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)?.cast<String?, Object?>();
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)
+          ?.cast<String?, Object?>();
     }
   }
 
   /// Returns the passed enum, to test asynchronous serialization and deserialization.
-  Future<AnEnum?> echoAsyncNullableEnum(AnEnum? arg_anEnum) async {
-    const String channelName =
+  Future<AnEnum?> echoAsyncNullableEnum(AnEnum? anEnum) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAsyncNullableEnum';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anEnum?.index]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anEnum?.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as int?) == null
+      return (__pigeon_replyList[0] as int?) == null
           ? null
-          : AnEnum.values[replyList[0]! as int];
+          : AnEnum.values[__pigeon_replyList[0]! as int];
     }
   }
 
   Future<void> callFlutterNoop() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterNoop';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -1721,544 +1923,566 @@ class HostIntegrationCoreApi {
   }
 
   Future<Object?> callFlutterThrowError() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterThrowError';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return replyList[0];
+      return __pigeon_replyList[0];
     }
   }
 
   Future<void> callFlutterThrowErrorFromVoid() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterThrowErrorFromVoid';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
     }
   }
 
-  Future<AllTypes> callFlutterEchoAllTypes(AllTypes arg_everything) async {
-    const String channelName =
+  Future<AllTypes> callFlutterEchoAllTypes(AllTypes everything) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoAllTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_everything]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[everything]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as AllTypes?)!;
+      return (__pigeon_replyList[0] as AllTypes?)!;
     }
   }
 
   Future<AllNullableTypes?> callFlutterEchoAllNullableTypes(
-      AllNullableTypes? arg_everything) async {
-    const String channelName =
+      AllNullableTypes? everything) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoAllNullableTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_everything]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[everything]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as AllNullableTypes?);
+      return (__pigeon_replyList[0] as AllNullableTypes?);
     }
   }
 
   Future<AllNullableTypes> callFlutterSendMultipleNullableTypes(
-      bool? arg_aNullableBool,
-      int? arg_aNullableInt,
-      String? arg_aNullableString) async {
-    const String channelName =
+      bool? aNullableBool, int? aNullableInt, String? aNullableString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterSendMultipleNullableTypes';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
-    );
-    final List<Object?>? replyList = await channel.send(
-            <Object?>[arg_aNullableBool, arg_aNullableInt, arg_aNullableString])
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+            .send(<Object?>[aNullableBool, aNullableInt, aNullableString])
         as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as AllNullableTypes?)!;
+      return (__pigeon_replyList[0] as AllNullableTypes?)!;
     }
   }
 
-  Future<bool> callFlutterEchoBool(bool arg_aBool) async {
-    const String channelName =
+  Future<bool> callFlutterEchoBool(bool aBool) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoBool';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aBool]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as bool?)!;
+      return (__pigeon_replyList[0] as bool?)!;
     }
   }
 
-  Future<int> callFlutterEchoInt(int arg_anInt) async {
-    const String channelName =
+  Future<int> callFlutterEchoInt(int anInt) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anInt]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 
-  Future<double> callFlutterEchoDouble(double arg_aDouble) async {
-    const String channelName =
+  Future<double> callFlutterEchoDouble(double aDouble) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoDouble';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aDouble]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as double?)!;
+      return (__pigeon_replyList[0] as double?)!;
     }
   }
 
-  Future<String> callFlutterEchoString(String arg_aString) async {
-    const String channelName =
+  Future<String> callFlutterEchoString(String aString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as String?)!;
+      return (__pigeon_replyList[0] as String?)!;
     }
   }
 
-  Future<Uint8List> callFlutterEchoUint8List(Uint8List arg_aList) async {
-    const String channelName =
+  Future<Uint8List> callFlutterEchoUint8List(Uint8List aList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoUint8List';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Uint8List?)!;
+      return (__pigeon_replyList[0] as Uint8List?)!;
     }
   }
 
-  Future<List<Object?>> callFlutterEchoList(List<Object?> arg_aList) async {
-    const String channelName =
+  Future<List<Object?>> callFlutterEchoList(List<Object?> aList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as List<Object?>?)!.cast<Object?>();
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<Object?>();
     }
   }
 
   Future<Map<String?, Object?>> callFlutterEchoMap(
-      Map<String?, Object?> arg_aMap) async {
-    const String channelName =
+      Map<String?, Object?> aMap) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aMap]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)!.cast<String?, Object?>();
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, Object?>();
     }
   }
 
-  Future<AnEnum> callFlutterEchoEnum(AnEnum arg_anEnum) async {
-    const String channelName =
+  Future<AnEnum> callFlutterEchoEnum(AnEnum anEnum) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoEnum';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anEnum.index]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anEnum.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return AnEnum.values[replyList[0]! as int];
+      return AnEnum.values[__pigeon_replyList[0]! as int];
     }
   }
 
-  Future<bool?> callFlutterEchoNullableBool(bool? arg_aBool) async {
-    const String channelName =
+  Future<bool?> callFlutterEchoNullableBool(bool? aBool) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableBool';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aBool]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as bool?);
+      return (__pigeon_replyList[0] as bool?);
     }
   }
 
-  Future<int?> callFlutterEchoNullableInt(int? arg_anInt) async {
-    const String channelName =
+  Future<int?> callFlutterEchoNullableInt(int? anInt) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anInt]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as int?);
+      return (__pigeon_replyList[0] as int?);
     }
   }
 
-  Future<double?> callFlutterEchoNullableDouble(double? arg_aDouble) async {
-    const String channelName =
+  Future<double?> callFlutterEchoNullableDouble(double? aDouble) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableDouble';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aDouble]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as double?);
+      return (__pigeon_replyList[0] as double?);
     }
   }
 
-  Future<String?> callFlutterEchoNullableString(String? arg_aString) async {
-    const String channelName =
+  Future<String?> callFlutterEchoNullableString(String? aString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as String?);
+      return (__pigeon_replyList[0] as String?);
     }
   }
 
-  Future<Uint8List?> callFlutterEchoNullableUint8List(
-      Uint8List? arg_aList) async {
-    const String channelName =
+  Future<Uint8List?> callFlutterEchoNullableUint8List(Uint8List? aList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableUint8List';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as Uint8List?);
+      return (__pigeon_replyList[0] as Uint8List?);
     }
   }
 
   Future<List<Object?>?> callFlutterEchoNullableList(
-      List<Object?>? arg_aList) async {
-    const String channelName =
+      List<Object?>? aList) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aList]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as List<Object?>?)?.cast<Object?>();
+      return (__pigeon_replyList[0] as List<Object?>?)?.cast<Object?>();
     }
   }
 
   Future<Map<String?, Object?>?> callFlutterEchoNullableMap(
-      Map<String?, Object?>? arg_aMap) async {
-    const String channelName =
+      Map<String?, Object?>? aMap) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aMap]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)?.cast<String?, Object?>();
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)
+          ?.cast<String?, Object?>();
     }
   }
 
-  Future<AnEnum?> callFlutterEchoNullableEnum(AnEnum? arg_anEnum) async {
-    const String channelName =
+  Future<AnEnum?> callFlutterEchoNullableEnum(AnEnum? anEnum) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.callFlutterEchoNullableEnum';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_anEnum?.index]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[anEnum?.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as int?) == null
+      return (__pigeon_replyList[0] as int?) == null
           ? null
-          : AnEnum.values[replyList[0]! as int];
+          : AnEnum.values[__pigeon_replyList[0]! as int];
     }
   }
 }
@@ -2304,7 +2528,8 @@ class _FlutterIntegrationCoreApiCodec extends StandardMessageCodec {
 /// The core interface that the Dart platform_test code implements for host
 /// integration tests to call into.
 abstract class FlutterIntegrationCoreApi {
-  static const MessageCodec<Object?> codec = _FlutterIntegrationCoreApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _FlutterIntegrationCoreApiCodec();
 
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic calling.
@@ -2386,14 +2611,15 @@ abstract class FlutterIntegrationCoreApi {
   static void setup(FlutterIntegrationCoreApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.noop',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           try {
             api.noop();
             return wrapResponse(empty: true);
@@ -2407,14 +2633,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.throwError',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           try {
             final Object? output = api.throwError();
             return wrapResponse(result: output);
@@ -2428,14 +2655,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.throwErrorFromVoid',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           try {
             api.throwErrorFromVoid();
             return wrapResponse(empty: true);
@@ -2449,14 +2677,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoAllTypes',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoAllTypes was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2476,14 +2705,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoAllNullableTypes',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoAllNullableTypes was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2503,14 +2733,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.sendMultipleNullableTypes',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.sendMultipleNullableTypes was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2531,14 +2762,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoBool',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoBool was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2558,14 +2790,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoInt',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoInt was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2585,14 +2818,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoDouble',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoDouble was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2612,14 +2846,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoString',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoString was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2639,14 +2874,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoUint8List',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoUint8List was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2666,14 +2902,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoList',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoList was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2694,14 +2931,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoMap',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoMap was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2722,14 +2960,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoEnum',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoEnum was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2750,14 +2989,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableBool',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableBool was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2775,14 +3015,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableInt',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableInt was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2800,14 +3041,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableDouble',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableDouble was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2825,14 +3067,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableString',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableString was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2850,14 +3093,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableUint8List',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableUint8List was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2875,14 +3119,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableList',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableList was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2901,14 +3146,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableMap',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableMap was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2927,14 +3173,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableEnum',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoNullableEnum was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -2953,14 +3200,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.noopAsync',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           try {
             await api.noopAsync();
             return wrapResponse(empty: true);
@@ -2974,14 +3222,15 @@ abstract class FlutterIntegrationCoreApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoAsyncString',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterIntegrationCoreApi.echoAsyncString was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -3009,27 +3258,30 @@ class HostTrivialApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   HostTrivialApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   Future<void> noop() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostTrivialApi.noop';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -3043,55 +3295,59 @@ class HostSmallApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   HostSmallApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
-  Future<String> echo(String arg_aString) async {
-    const String channelName =
+  Future<String> echo(String aString) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.echo';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_aString]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as String?)!;
+      return (__pigeon_replyList[0] as String?)!;
     }
   }
 
   Future<void> voidVoid() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.HostSmallApi.voidVoid';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -3124,7 +3380,8 @@ class _FlutterSmallApiCodec extends StandardMessageCodec {
 
 /// A simple API called in some unit tests.
 abstract class FlutterSmallApi {
-  static const MessageCodec<Object?> codec = _FlutterSmallApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _FlutterSmallApiCodec();
 
   TestMessage echoWrappedList(TestMessage msg);
 
@@ -3132,14 +3389,15 @@ abstract class FlutterSmallApi {
 
   static void setup(FlutterSmallApi? api, {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterSmallApi.echoWrappedList',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterSmallApi.echoWrappedList was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -3159,14 +3417,15 @@ abstract class FlutterSmallApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.FlutterSmallApi.echoString',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.FlutterSmallApi.echoString was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
index 9f3c469c9b8..8354d159d33 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -94,37 +94,38 @@ class EnumApi2Host {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   EnumApi2Host({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _EnumApi2HostCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _EnumApi2HostCodec();
 
   /// This comment is to test method documentation comments.
-  Future<DataWithEnum> echo(DataWithEnum arg_data) async {
-    const String channelName =
+  Future<DataWithEnum> echo(DataWithEnum data) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.EnumApi2Host.echo';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_data]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[data]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as DataWithEnum?)!;
+      return (__pigeon_replyList[0] as DataWithEnum?)!;
     }
   }
 }
@@ -154,21 +155,23 @@ class _EnumApi2FlutterCodec extends StandardMessageCodec {
 
 /// This comment is to test api documentation comments.
 abstract class EnumApi2Flutter {
-  static const MessageCodec<Object?> codec = _EnumApi2FlutterCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _EnumApi2FlutterCodec();
 
   /// This comment is to test method documentation comments.
   DataWithEnum echo(DataWithEnum data);
 
   static void setup(EnumApi2Flutter? api, {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.EnumApi2Flutter.echo',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.EnumApi2Flutter.echo was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
index 8b149d7942e..73f100cf28b 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -150,121 +150,125 @@ class Api {
   /// Constructor for [Api].  The [binaryMessenger] named argument is
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
-  Api({BinaryMessenger? binaryMessenger}) : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+  Api({BinaryMessenger? binaryMessenger})
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _ApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _ApiCodec();
 
-  Future<FlutterSearchReply> search(FlutterSearchRequest arg_request) async {
-    const String channelName =
+  Future<FlutterSearchReply> search(FlutterSearchRequest request) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.Api.search';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_request]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[request]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as FlutterSearchReply?)!;
+      return (__pigeon_replyList[0] as FlutterSearchReply?)!;
     }
   }
 
-  Future<FlutterSearchReplies> doSearches(
-      FlutterSearchRequests arg_request) async {
-    const String channelName =
+  Future<FlutterSearchReplies> doSearches(FlutterSearchRequests request) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.Api.doSearches';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_request]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[request]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as FlutterSearchReplies?)!;
+      return (__pigeon_replyList[0] as FlutterSearchReplies?)!;
     }
   }
 
-  Future<FlutterSearchRequests> echo(FlutterSearchRequests arg_requests) async {
-    const String channelName =
+  Future<FlutterSearchRequests> echo(FlutterSearchRequests requests) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.Api.echo';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_requests]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[requests]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as FlutterSearchRequests?)!;
+      return (__pigeon_replyList[0] as FlutterSearchRequests?)!;
     }
   }
 
-  Future<int> anInt(int arg_value) async {
-    const String channelName =
+  Future<int> anInt(int value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.Api.anInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 }
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
index fa0084706ff..cc7b8b53c36 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -180,30 +180,32 @@ class MessageApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   MessageApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _MessageApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec = _MessageApiCodec();
 
   /// This comment is to test documentation comments.
   ///
   /// This comment also tests multiple line comments.
   Future<void> initialize() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.MessageApi.initialize';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
       return;
@@ -211,31 +213,32 @@ class MessageApi {
   }
 
   /// This comment is to test method documentation comments.
-  Future<MessageSearchReply> search(MessageSearchRequest arg_request) async {
-    const String channelName =
+  Future<MessageSearchReply> search(MessageSearchRequest request) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.MessageApi.search';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_request]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[request]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as MessageSearchReply?)!;
+      return (__pigeon_replyList[0] as MessageSearchReply?)!;
     }
   }
 }
@@ -279,39 +282,41 @@ class MessageNestedApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   MessageNestedApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _MessageNestedApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _MessageNestedApiCodec();
 
   /// This comment is to test method documentation comments.
   ///
   /// This comment also tests multiple line comments.
-  Future<MessageSearchReply> search(MessageNested arg_nested) async {
-    const String channelName =
+  Future<MessageSearchReply> search(MessageNested nested) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.MessageNestedApi.search';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_nested]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[nested]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as MessageSearchReply?)!;
+      return (__pigeon_replyList[0] as MessageSearchReply?)!;
     }
   }
 }
@@ -346,7 +351,8 @@ class _MessageFlutterSearchApiCodec extends StandardMessageCodec {
 
 /// This comment is to test api documentation comments.
 abstract class MessageFlutterSearchApi {
-  static const MessageCodec<Object?> codec = _MessageFlutterSearchApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _MessageFlutterSearchApiCodec();
 
   /// This comment is to test method documentation comments.
   MessageSearchReply search(MessageSearchRequest request);
@@ -354,14 +360,15 @@ abstract class MessageFlutterSearchApi {
   static void setup(MessageFlutterSearchApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.MessageFlutterSearchApi.search',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.MessageFlutterSearchApi.search was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
index 2922865d9aa..bec054b4be4 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -35,56 +35,60 @@ class MultipleArityHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   MultipleArityHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
-  Future<int> subtract(int arg_x, int arg_y) async {
-    const String channelName =
+  Future<int> subtract(int x, int y) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.MultipleArityHostApi.subtract';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_x, arg_y]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[x, y]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 }
 
 abstract class MultipleArityFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   int subtract(int x, int y);
 
   static void setup(MultipleArityFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.MultipleArityFlutterApi.subtract',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.MultipleArityFlutterApi.subtract was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
index 3a40af18716..7279e85c40e 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -161,37 +161,39 @@ class NonNullFieldHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   NonNullFieldHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _NonNullFieldHostApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _NonNullFieldHostApiCodec();
 
   Future<NonNullFieldSearchReply> search(
-      NonNullFieldSearchRequest arg_nested) async {
-    const String channelName =
+      NonNullFieldSearchRequest nested) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.NonNullFieldHostApi.search';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_nested]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[nested]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as NonNullFieldSearchReply?)!;
+      return (__pigeon_replyList[0] as NonNullFieldSearchReply?)!;
     }
   }
 }
@@ -230,21 +232,23 @@ class _NonNullFieldFlutterApiCodec extends StandardMessageCodec {
 }
 
 abstract class NonNullFieldFlutterApi {
-  static const MessageCodec<Object?> codec = _NonNullFieldFlutterApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _NonNullFieldFlutterApiCodec();
 
   NonNullFieldSearchReply search(NonNullFieldSearchRequest request);
 
   static void setup(NonNullFieldFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.NonNullFieldFlutterApi.search',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.NonNullFieldFlutterApi.search was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
index 863897535cb..ecf7c7f7e97 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -139,37 +139,38 @@ class NullFieldsHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   NullFieldsHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _NullFieldsHostApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _NullFieldsHostApiCodec();
 
-  Future<NullFieldsSearchReply> search(
-      NullFieldsSearchRequest arg_nested) async {
-    const String channelName =
+  Future<NullFieldsSearchReply> search(NullFieldsSearchRequest nested) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.NullFieldsHostApi.search';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_nested]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[nested]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as NullFieldsSearchReply?)!;
+      return (__pigeon_replyList[0] as NullFieldsSearchReply?)!;
     }
   }
 }
@@ -203,21 +204,23 @@ class _NullFieldsFlutterApiCodec extends StandardMessageCodec {
 }
 
 abstract class NullFieldsFlutterApi {
-  static const MessageCodec<Object?> codec = _NullFieldsFlutterApiCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      _NullFieldsFlutterApiCodec();
 
   NullFieldsSearchReply search(NullFieldsSearchRequest request);
 
   static void setup(NullFieldsFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.NullFieldsFlutterApi.search',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.NullFieldsFlutterApi.search was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
index c7f71206ee3..dd1665a463c 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -35,50 +35,55 @@ class NullableReturnHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   NullableReturnHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   Future<int?> doit() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.NullableReturnHostApi.doit';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as int?);
+      return (__pigeon_replyList[0] as int?);
     }
   }
 }
 
 abstract class NullableReturnFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   int? doit();
 
   static void setup(NullableReturnFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.NullableReturnFlutterApi.doit',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           try {
             final int? output = api.doit();
             return wrapResponse(result: output);
@@ -99,56 +104,60 @@ class NullableArgHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   NullableArgHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
-  Future<int> doit(int? arg_x) async {
-    const String channelName =
+  Future<int> doit(int? x) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.NullableArgHostApi.doit';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_x]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[x]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 }
 
 abstract class NullableArgFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   int? doit(int? x);
 
   static void setup(NullableArgFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.NullableArgFlutterApi.doit',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.NullableArgFlutterApi.doit was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -173,50 +182,55 @@ class NullableCollectionReturnHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   NullableCollectionReturnHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   Future<List<String?>?> doit() async {
-    const String channelName =
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionReturnHostApi.doit';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
     } else {
-      return (replyList[0] as List<Object?>?)?.cast<String?>();
+      return (__pigeon_replyList[0] as List<Object?>?)?.cast<String?>();
     }
   }
 }
 
 abstract class NullableCollectionReturnFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   List<String?>? doit();
 
   static void setup(NullableCollectionReturnFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionReturnFlutterApi.doit',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           try {
             final List<String?>? output = api.doit();
             return wrapResponse(result: output);
@@ -237,56 +251,60 @@ class NullableCollectionArgHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   NullableCollectionArgHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
-  Future<List<String?>> doit(List<String?>? arg_x) async {
-    const String channelName =
+  Future<List<String?>> doit(List<String?>? x) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionArgHostApi.doit';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_x]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[x]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as List<Object?>?)!.cast<String?>();
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<String?>();
     }
   }
 }
 
 abstract class NullableCollectionArgFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   List<String?> doit(List<String?>? x);
 
   static void setup(NullableCollectionArgFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionArgFlutterApi.doit',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionArgFlutterApi.doit was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
index d5387984bab..72c115d6527 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
@@ -35,266 +35,278 @@ class PrimitiveHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   PrimitiveHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : __pigeon_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? __pigeon_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
-  Future<int> anInt(int arg_value) async {
-    const String channelName =
+  Future<int> anInt(int value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.anInt';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return (__pigeon_replyList[0] as int?)!;
     }
   }
 
-  Future<bool> aBool(bool arg_value) async {
-    const String channelName =
+  Future<bool> aBool(bool value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aBool';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as bool?)!;
+      return (__pigeon_replyList[0] as bool?)!;
     }
   }
 
-  Future<String> aString(String arg_value) async {
-    const String channelName =
+  Future<String> aString(String value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aString';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as String?)!;
+      return (__pigeon_replyList[0] as String?)!;
     }
   }
 
-  Future<double> aDouble(double arg_value) async {
-    const String channelName =
+  Future<double> aDouble(double value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aDouble';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as double?)!;
+      return (__pigeon_replyList[0] as double?)!;
     }
   }
 
-  Future<Map<Object?, Object?>> aMap(Map<Object?, Object?> arg_value) async {
-    const String channelName =
+  Future<Map<Object?, Object?>> aMap(Map<Object?, Object?> value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)!;
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!;
     }
   }
 
-  Future<List<Object?>> aList(List<Object?> arg_value) async {
-    const String channelName =
+  Future<List<Object?>> aList(List<Object?> value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as List<Object?>?)!;
+      return (__pigeon_replyList[0] as List<Object?>?)!;
     }
   }
 
-  Future<Int32List> anInt32List(Int32List arg_value) async {
-    const String channelName =
+  Future<Int32List> anInt32List(Int32List value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.anInt32List';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Int32List?)!;
+      return (__pigeon_replyList[0] as Int32List?)!;
     }
   }
 
-  Future<List<bool?>> aBoolList(List<bool?> arg_value) async {
-    const String channelName =
+  Future<List<bool?>> aBoolList(List<bool?> value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aBoolList';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as List<Object?>?)!.cast<bool?>();
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<bool?>();
     }
   }
 
-  Future<Map<String?, int?>> aStringIntMap(Map<String?, int?> arg_value) async {
-    const String channelName =
+  Future<Map<String?, int?>> aStringIntMap(Map<String?, int?> value) async {
+    const String __pigeon_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aStringIntMap';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[arg_value]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[value]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if (__pigeon_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as Map<Object?, Object?>?)!.cast<String?, int?>();
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, int?>();
     }
   }
 }
 
 abstract class PrimitiveFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
 
   int anInt(int value);
 
@@ -317,14 +329,15 @@ abstract class PrimitiveFlutterApi {
   static void setup(PrimitiveFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.anInt',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.anInt was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -344,14 +357,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aBool',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aBool was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -371,14 +385,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aString',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aString was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -398,14 +413,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aDouble',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aDouble was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -425,14 +441,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aMap',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aMap was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -453,14 +470,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aList',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aList was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -480,14 +498,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.anInt32List',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.anInt32List was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -507,14 +526,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aBoolList',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aBoolList was null.');
           final List<Object?> args = (message as List<Object?>?)!;
@@ -535,14 +555,15 @@ abstract class PrimitiveFlutterApi {
       }
     }
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aStringIntMap',
-          codec,
+          pigeonChannelCodec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        __pigeon_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        __pigeon_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_integration_tests.PrimitiveFlutterApi.aStringIntMap was null.');
           final List<Object?> args = (message as List<Object?>?)!;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/multiple_arity_test.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/multiple_arity_test.dart
index d446a036f74..64063f84786 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/test/multiple_arity_test.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/multiple_arity_test.dart
@@ -18,12 +18,13 @@ void main() {
             'dev.flutter.pigeon.pigeon_integration_tests.MultipleArityHostApi.subtract',
             any))
         .thenAnswer((Invocation realInvocation) async {
-      final Object input = MultipleArityHostApi.codec
+      final Object input = MultipleArityHostApi.pigeonChannelCodec
           .decodeMessage(realInvocation.positionalArguments[1] as ByteData?)!;
       final List<Object?> args = input as List<Object?>;
       final int x = (args[0] as int?)!;
       final int y = (args[1] as int?)!;
-      return MultipleArityHostApi.codec.encodeMessage(<Object>[x - y]);
+      return MultipleArityHostApi.pigeonChannelCodec
+          .encodeMessage(<Object>[x - y]);
     });
 
     final MultipleArityHostApi api =
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_safe_test.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_safe_test.dart
index 28c341d6f0d..966c8ac99b3 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_safe_test.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/null_safe_test.dart
@@ -50,7 +50,7 @@ void main() {
     final FlutterSearchReply reply = FlutterSearchReply()..result = 'ho';
     final BinaryMessenger mockMessenger = MockBinaryMessenger();
     final Completer<ByteData?> completer = Completer<ByteData?>();
-    completer.complete(Api.codec.encodeMessage(<Object>[reply]));
+    completer.complete(Api.pigeonChannelCodec.encodeMessage(<Object>[reply]));
     final Future<ByteData?> sendResult = completer.future;
     when(mockMessenger.send(
             'dev.flutter.pigeon.pigeon_integration_tests.Api.search', any))
@@ -69,7 +69,7 @@ void main() {
     echoOneArgument(
       mockMessenger,
       'dev.flutter.pigeon.pigeon_integration_tests.Api.echo',
-      Api.codec,
+      Api.pigeonChannelCodec,
     );
     final Api api = Api(binaryMessenger: mockMessenger);
     final FlutterSearchRequests echo = await api.echo(requests);
@@ -82,7 +82,7 @@ void main() {
     echoOneArgument(
       mockMessenger,
       'dev.flutter.pigeon.pigeon_integration_tests.Api.anInt',
-      Api.codec,
+      Api.pigeonChannelCodec,
     );
     final Api api = Api(binaryMessenger: mockMessenger);
     final int result = await api.anInt(1);
@@ -95,7 +95,7 @@ void main() {
         'dev.flutter.pigeon.pigeon_integration_tests.Api.anInt';
     when(mockMessenger.send(channel, any))
         .thenAnswer((Invocation realInvocation) async {
-      return Api.codec.encodeMessage(<Object?>[null]);
+      return Api.pigeonChannelCodec.encodeMessage(<Object?>[null]);
     });
     final Api api = Api(binaryMessenger: mockMessenger);
     expect(() async => api.anInt(1),
@@ -108,7 +108,7 @@ void main() {
         'dev.flutter.pigeon.pigeon_integration_tests.NullableArgHostApi.doit';
     when(mockMessenger.send(channel, any))
         .thenAnswer((Invocation realInvocation) async {
-      return Api.codec.encodeMessage(<Object?>[123]);
+      return Api.pigeonChannelCodec.encodeMessage(<Object?>[123]);
     });
     final NullableArgHostApi api =
         NullableArgHostApi(binaryMessenger: mockMessenger);
@@ -121,7 +121,7 @@ void main() {
         'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionArgHostApi.doit';
     when(mockMessenger.send(channel, any))
         .thenAnswer((Invocation realInvocation) async {
-      return Api.codec.encodeMessage(<Object?>[
+      return Api.pigeonChannelCodec.encodeMessage(<Object?>[
         <String?>['123']
       ]);
     });
@@ -140,10 +140,11 @@ void main() {
     final Completer<int> resultCompleter = Completer<int>();
     binding.defaultBinaryMessenger.handlePlatformMessage(
       'dev.flutter.pigeon.pigeon_integration_tests.NullableArgFlutterApi.doit',
-      NullableArgFlutterApi.codec.encodeMessage(<Object?>[null]),
+      NullableArgFlutterApi.pigeonChannelCodec.encodeMessage(<Object?>[null]),
       (ByteData? data) {
         resultCompleter.complete(
-          (NullableArgFlutterApi.codec.decodeMessage(data)! as List<Object?>)
+          (NullableArgFlutterApi.pigeonChannelCodec.decodeMessage(data)!
+                  as List<Object?>)
               .first! as int,
         );
       },
@@ -165,11 +166,12 @@ void main() {
     final Completer<List<String?>> resultCompleter = Completer<List<String?>>();
     binding.defaultBinaryMessenger.handlePlatformMessage(
       'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionArgFlutterApi.doit',
-      NullableCollectionArgFlutterApi.codec.encodeMessage(<Object?>[null]),
+      NullableCollectionArgFlutterApi.pigeonChannelCodec
+          .encodeMessage(<Object?>[null]),
       (ByteData? data) {
         resultCompleter.complete(
-          ((NullableCollectionArgFlutterApi.codec.decodeMessage(data)!
-                      as List<Object?>)
+          ((NullableCollectionArgFlutterApi.pigeonChannelCodec
+                      .decodeMessage(data)! as List<Object?>)
                   .first! as List<Object?>)
               .cast<String>(),
         );
@@ -188,7 +190,8 @@ void main() {
         'dev.flutter.pigeon.pigeon_integration_tests.NullableReturnHostApi.doit';
     when(mockMessenger.send(channel, any))
         .thenAnswer((Invocation realInvocation) async {
-      return NullableReturnHostApi.codec.encodeMessage(<Object?>[null]);
+      return NullableReturnHostApi.pigeonChannelCodec
+          .encodeMessage(<Object?>[null]);
     });
     final NullableReturnHostApi api =
         NullableReturnHostApi(binaryMessenger: mockMessenger);
@@ -201,7 +204,7 @@ void main() {
         'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionReturnHostApi.doit';
     when(mockMessenger.send(channel, any))
         .thenAnswer((Invocation realInvocation) async {
-      return NullableCollectionReturnHostApi.codec
+      return NullableCollectionReturnHostApi.pigeonChannelCodec
           .encodeMessage(<Object?>[null]);
     });
     final NullableCollectionReturnHostApi api =
@@ -219,7 +222,7 @@ void main() {
     final Completer<int?> resultCompleter = Completer<int?>();
     unawaited(binding.defaultBinaryMessenger.handlePlatformMessage(
       'dev.flutter.pigeon.pigeon_integration_tests.NullableReturnFlutterApi.doit',
-      NullableReturnFlutterApi.codec.encodeMessage(<Object?>[]),
+      NullableReturnFlutterApi.pigeonChannelCodec.encodeMessage(<Object?>[]),
       (ByteData? data) {
         resultCompleter.complete(null);
       },
@@ -242,7 +245,8 @@ void main() {
         Completer<List<String?>?>();
     unawaited(binding.defaultBinaryMessenger.handlePlatformMessage(
       'dev.flutter.pigeon.pigeon_integration_tests.NullableCollectionReturnFlutterApi.doit',
-      NullableCollectionReturnFlutterApi.codec.encodeMessage(<Object?>[]),
+      NullableCollectionReturnFlutterApi.pigeonChannelCodec
+          .encodeMessage(<Object?>[]),
       (ByteData? data) {
         resultCompleter.complete(null);
       },
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/primitive_test.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/primitive_test.dart
index e024f9c60d8..3623ee1f5e6 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/test/primitive_test.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/primitive_test.dart
@@ -18,7 +18,7 @@ void main() {
     echoOneArgument(
       mockMessenger,
       'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.anInt',
-      PrimitiveHostApi.codec,
+      PrimitiveHostApi.pigeonChannelCodec,
     );
     final PrimitiveHostApi api =
         PrimitiveHostApi(binaryMessenger: mockMessenger);
@@ -31,7 +31,7 @@ void main() {
     echoOneArgument(
       mockMessenger,
       'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aBoolList',
-      PrimitiveHostApi.codec,
+      PrimitiveHostApi.pigeonChannelCodec,
     );
     final PrimitiveHostApi api =
         PrimitiveHostApi(binaryMessenger: mockMessenger);
@@ -49,7 +49,7 @@ void main() {
         .thenAnswer((Invocation realInvocation) {
       final MessageHandler? handler =
           realInvocation.positionalArguments[1] as MessageHandler?;
-      handler!(PrimitiveFlutterApi.codec.encodeMessage(<Object?>[
+      handler!(PrimitiveFlutterApi.pigeonChannelCodec.encodeMessage(<Object?>[
         <Object?>[true, false]
       ]));
     });
@@ -62,7 +62,7 @@ void main() {
     echoOneArgument(
       mockMessenger,
       'dev.flutter.pigeon.pigeon_integration_tests.PrimitiveHostApi.aStringIntMap',
-      PrimitiveHostApi.codec,
+      PrimitiveHostApi.pigeonChannelCodec,
     );
     final PrimitiveHostApi api =
         PrimitiveHostApi(binaryMessenger: mockMessenger);
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
index 47e2008276e..e1c371cf1e0 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
@@ -348,6 +348,12 @@ interface HostIntegrationCoreApi {
   fun echoClassWrapper(wrapper: AllClassesWrapper): AllClassesWrapper
   /** Returns the passed enum to test serialization and deserialization. */
   fun echoEnum(anEnum: AnEnum): AnEnum
+  /** Returns the default string. */
+  fun echoNamedDefaultString(aString: String): String
+  /** Returns passed in double. */
+  fun echoOptionalDefaultDouble(aDouble: Double): Double
+  /** Returns passed in int. */
+  fun echoRequiredInt(anInt: Long): Long
   /** Returns the passed object, to test serialization and deserialization. */
   fun echoAllNullableTypes(everything: AllNullableTypes?): AllNullableTypes?
   /**
@@ -382,6 +388,10 @@ interface HostIntegrationCoreApi {
   fun echoNullableMap(aNullableMap: Map<String?, Any?>?): Map<String?, Any?>?
 
   fun echoNullableEnum(anEnum: AnEnum?): AnEnum?
+  /** Returns passed in int. */
+  fun echoOptionalNullableInt(aNullableInt: Long?): Long?
+  /** Returns the passed in string. */
+  fun echoNamedNullableString(aNullableString: String?): String?
   /**
    * A no-op function taking no arguments and returning no value, to sanity test basic asynchronous
    * calling.
@@ -828,6 +838,72 @@ interface HostIntegrationCoreApi {
           channel.setMessageHandler(null)
         }
       }
+      run {
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedDefaultString",
+                codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val aStringArg = args[0] as String
+            var wrapped: List<Any?>
+            try {
+              wrapped = listOf<Any?>(api.echoNamedDefaultString(aStringArg))
+            } catch (exception: Throwable) {
+              wrapped = wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalDefaultDouble",
+                codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val aDoubleArg = args[0] as Double
+            var wrapped: List<Any?>
+            try {
+              wrapped = listOf<Any?>(api.echoOptionalDefaultDouble(aDoubleArg))
+            } catch (exception: Throwable) {
+              wrapped = wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoRequiredInt",
+                codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val anIntArg = args[0].let { if (it is Int) it.toLong() else it as Long }
+            var wrapped: List<Any?>
+            try {
+              wrapped = listOf<Any?>(api.echoRequiredInt(anIntArg))
+            } catch (exception: Throwable) {
+              wrapped = wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
       run {
         val channel =
             BasicMessageChannel<Any?>(
@@ -1119,6 +1195,50 @@ interface HostIntegrationCoreApi {
           channel.setMessageHandler(null)
         }
       }
+      run {
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalNullableInt",
+                codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val aNullableIntArg = args[0].let { if (it is Int) it.toLong() else it as Long? }
+            var wrapped: List<Any?>
+            try {
+              wrapped = listOf<Any?>(api.echoOptionalNullableInt(aNullableIntArg))
+            } catch (exception: Throwable) {
+              wrapped = wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+      run {
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedNullableString",
+                codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val aNullableStringArg = args[0] as String?
+            var wrapped: List<Any?>
+            try {
+              wrapped = listOf<Any?>(api.echoNamedNullableString(aNullableStringArg))
+            } catch (exception: Throwable) {
+              wrapped = wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
       run {
         val channel =
             BasicMessageChannel<Any?>(
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt
index a5345170985..8b4e8bc4fb1 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/TestPlugin.kt
@@ -82,6 +82,18 @@ class TestPlugin : FlutterPlugin, HostIntegrationCoreApi {
     return anEnum
   }
 
+  override fun echoNamedDefaultString(aString: String): String {
+    return aString
+  }
+
+  override fun echoOptionalDefaultDouble(aDouble: Double): Double {
+    return aDouble
+  }
+
+  override fun echoRequiredInt(anInt: Long): Long {
+    return anInt
+  }
+
   override fun extractNestedNullableString(wrapper: AllClassesWrapper): String? {
     return wrapper.allNullableTypes.aNullableString
   }
@@ -137,6 +149,14 @@ class TestPlugin : FlutterPlugin, HostIntegrationCoreApi {
     return anEnum
   }
 
+  override fun echoOptionalNullableInt(aNullableInt: Long?): Long? {
+    return aNullableInt
+  }
+
+  override fun echoNamedNullableString(aNullableString: String?): String? {
+    return aNullableString
+  }
+
   override fun noopAsync(callback: (Result<Unit>) -> Unit) {
     callback(Result.success(Unit))
   }
diff --git a/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift b/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift
index 40aee78946d..773b6e5c12e 100644
--- a/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift
+++ b/packages/pigeon/platform_tests/test_plugin/ios/Classes/CoreTests.gen.swift
@@ -342,6 +342,12 @@ protocol HostIntegrationCoreApi {
   func echo(_ wrapper: AllClassesWrapper) throws -> AllClassesWrapper
   /// Returns the passed enum to test serialization and deserialization.
   func echo(_ anEnum: AnEnum) throws -> AnEnum
+  /// Returns the default string.
+  func echoNamedDefault(_ aString: String) throws -> String
+  /// Returns passed in double.
+  func echoOptionalDefault(_ aDouble: Double) throws -> Double
+  /// Returns passed in int.
+  func echoRequired(_ anInt: Int64) throws -> Int64
   /// Returns the passed object, to test serialization and deserialization.
   func echo(_ everything: AllNullableTypes?) throws -> AllNullableTypes?
   /// Returns the inner `aString` value from the wrapped object, to test
@@ -369,6 +375,10 @@ protocol HostIntegrationCoreApi {
   /// Returns the passed map, to test serialization and deserialization.
   func echoNullable(_ aNullableMap: [String?: Any?]?) throws -> [String?: Any?]?
   func echoNullable(_ anEnum: AnEnum?) throws -> AnEnum?
+  /// Returns passed in int.
+  func echoOptional(_ aNullableInt: Int64?) throws -> Int64?
+  /// Returns the passed in string.
+  func echoNamed(_ aNullableString: String?) throws -> String?
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic asynchronous calling.
   func noopAsync(completion: @escaping (Result<Void, Error>) -> Void)
@@ -681,6 +691,54 @@ class HostIntegrationCoreApiSetup {
     } else {
       echoEnumChannel.setMessageHandler(nil)
     }
+    /// Returns the default string.
+    let echoNamedDefaultStringChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedDefaultString", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoNamedDefaultStringChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aStringArg = args[0] as! String
+        do {
+          let result = try api.echoNamedDefault(aStringArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoNamedDefaultStringChannel.setMessageHandler(nil)
+    }
+    /// Returns passed in double.
+    let echoOptionalDefaultDoubleChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalDefaultDouble", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoOptionalDefaultDoubleChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aDoubleArg = args[0] as! Double
+        do {
+          let result = try api.echoOptionalDefault(aDoubleArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoOptionalDefaultDoubleChannel.setMessageHandler(nil)
+    }
+    /// Returns passed in int.
+    let echoRequiredIntChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoRequiredInt", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoRequiredIntChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let anIntArg = args[0] is Int64 ? args[0] as! Int64 : Int64(args[0] as! Int32)
+        do {
+          let result = try api.echoRequired(anIntArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoRequiredIntChannel.setMessageHandler(nil)
+    }
     /// Returns the passed object, to test serialization and deserialization.
     let echoAllNullableTypesChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAllNullableTypes", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
@@ -892,6 +950,38 @@ class HostIntegrationCoreApiSetup {
     } else {
       echoNullableEnumChannel.setMessageHandler(nil)
     }
+    /// Returns passed in int.
+    let echoOptionalNullableIntChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalNullableInt", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoOptionalNullableIntChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aNullableIntArg: Int64? = isNullish(args[0]) ? nil : (args[0] is Int64? ? args[0] as! Int64? : Int64(args[0] as! Int32))
+        do {
+          let result = try api.echoOptional(aNullableIntArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoOptionalNullableIntChannel.setMessageHandler(nil)
+    }
+    /// Returns the passed in string.
+    let echoNamedNullableStringChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedNullableString", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoNamedNullableStringChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aNullableStringArg: String? = nilOrValue(args[0])
+        do {
+          let result = try api.echoNamed(aNullableStringArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoNamedNullableStringChannel.setMessageHandler(nil)
+    }
     /// A no-op function taking no arguments and returning no value, to sanity
     /// test basic asynchronous calling.
     let noopAsyncChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.noopAsync", binaryMessenger: binaryMessenger, codec: codec)
diff --git a/packages/pigeon/platform_tests/test_plugin/ios/Classes/TestPlugin.swift b/packages/pigeon/platform_tests/test_plugin/ios/Classes/TestPlugin.swift
index c29d1eef003..8b4daf5a08e 100644
--- a/packages/pigeon/platform_tests/test_plugin/ios/Classes/TestPlugin.swift
+++ b/packages/pigeon/platform_tests/test_plugin/ios/Classes/TestPlugin.swift
@@ -126,6 +126,18 @@ public class TestPlugin: NSObject, FlutterPlugin, HostIntegrationCoreApi {
     return aNullableObject
   }
 
+  func echoNamedDefault(_ aString: String) throws -> String {
+    return aString
+  }
+
+  func echoOptionalDefault(_ aDouble: Double) throws -> Double {
+    return aDouble
+  }
+
+  func echoRequired(_ anInt: Int64) throws -> Int64 {
+    return anInt
+  }
+
   func echoNullable(_ aNullableList: [Any?]?) throws -> [Any?]? {
     return aNullableList
   }
@@ -138,6 +150,14 @@ public class TestPlugin: NSObject, FlutterPlugin, HostIntegrationCoreApi {
     return anEnum
   }
 
+  func echoOptional(_ aNullableInt: Int64?) throws -> Int64? {
+    return aNullableInt
+  }
+
+  func echoNamed(_ aNullableString: String?) throws -> String? {
+    return aNullableString
+  }
+
   func noopAsync(completion: @escaping (Result<Void, Error>) -> Void) {
     completion(.success(Void()))
   }
diff --git a/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift b/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift
index 40aee78946d..773b6e5c12e 100644
--- a/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift
+++ b/packages/pigeon/platform_tests/test_plugin/macos/Classes/CoreTests.gen.swift
@@ -342,6 +342,12 @@ protocol HostIntegrationCoreApi {
   func echo(_ wrapper: AllClassesWrapper) throws -> AllClassesWrapper
   /// Returns the passed enum to test serialization and deserialization.
   func echo(_ anEnum: AnEnum) throws -> AnEnum
+  /// Returns the default string.
+  func echoNamedDefault(_ aString: String) throws -> String
+  /// Returns passed in double.
+  func echoOptionalDefault(_ aDouble: Double) throws -> Double
+  /// Returns passed in int.
+  func echoRequired(_ anInt: Int64) throws -> Int64
   /// Returns the passed object, to test serialization and deserialization.
   func echo(_ everything: AllNullableTypes?) throws -> AllNullableTypes?
   /// Returns the inner `aString` value from the wrapped object, to test
@@ -369,6 +375,10 @@ protocol HostIntegrationCoreApi {
   /// Returns the passed map, to test serialization and deserialization.
   func echoNullable(_ aNullableMap: [String?: Any?]?) throws -> [String?: Any?]?
   func echoNullable(_ anEnum: AnEnum?) throws -> AnEnum?
+  /// Returns passed in int.
+  func echoOptional(_ aNullableInt: Int64?) throws -> Int64?
+  /// Returns the passed in string.
+  func echoNamed(_ aNullableString: String?) throws -> String?
   /// A no-op function taking no arguments and returning no value, to sanity
   /// test basic asynchronous calling.
   func noopAsync(completion: @escaping (Result<Void, Error>) -> Void)
@@ -681,6 +691,54 @@ class HostIntegrationCoreApiSetup {
     } else {
       echoEnumChannel.setMessageHandler(nil)
     }
+    /// Returns the default string.
+    let echoNamedDefaultStringChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedDefaultString", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoNamedDefaultStringChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aStringArg = args[0] as! String
+        do {
+          let result = try api.echoNamedDefault(aStringArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoNamedDefaultStringChannel.setMessageHandler(nil)
+    }
+    /// Returns passed in double.
+    let echoOptionalDefaultDoubleChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalDefaultDouble", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoOptionalDefaultDoubleChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aDoubleArg = args[0] as! Double
+        do {
+          let result = try api.echoOptionalDefault(aDoubleArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoOptionalDefaultDoubleChannel.setMessageHandler(nil)
+    }
+    /// Returns passed in int.
+    let echoRequiredIntChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoRequiredInt", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoRequiredIntChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let anIntArg = args[0] is Int64 ? args[0] as! Int64 : Int64(args[0] as! Int32)
+        do {
+          let result = try api.echoRequired(anIntArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoRequiredIntChannel.setMessageHandler(nil)
+    }
     /// Returns the passed object, to test serialization and deserialization.
     let echoAllNullableTypesChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoAllNullableTypes", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
@@ -892,6 +950,38 @@ class HostIntegrationCoreApiSetup {
     } else {
       echoNullableEnumChannel.setMessageHandler(nil)
     }
+    /// Returns passed in int.
+    let echoOptionalNullableIntChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoOptionalNullableInt", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoOptionalNullableIntChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aNullableIntArg: Int64? = isNullish(args[0]) ? nil : (args[0] is Int64? ? args[0] as! Int64? : Int64(args[0] as! Int32))
+        do {
+          let result = try api.echoOptional(aNullableIntArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoOptionalNullableIntChannel.setMessageHandler(nil)
+    }
+    /// Returns the passed in string.
+    let echoNamedNullableStringChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.echoNamedNullableString", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      echoNamedNullableStringChannel.setMessageHandler { message, reply in
+        let args = message as! [Any?]
+        let aNullableStringArg: String? = nilOrValue(args[0])
+        do {
+          let result = try api.echoNamed(aNullableStringArg)
+          reply(wrapResult(result))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      echoNamedNullableStringChannel.setMessageHandler(nil)
+    }
     /// A no-op function taking no arguments and returning no value, to sanity
     /// test basic asynchronous calling.
     let noopAsyncChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi.noopAsync", binaryMessenger: binaryMessenger, codec: codec)
diff --git a/packages/pigeon/platform_tests/test_plugin/macos/Classes/TestPlugin.swift b/packages/pigeon/platform_tests/test_plugin/macos/Classes/TestPlugin.swift
index 3ed31b60d65..c82f94b1c0b 100644
--- a/packages/pigeon/platform_tests/test_plugin/macos/Classes/TestPlugin.swift
+++ b/packages/pigeon/platform_tests/test_plugin/macos/Classes/TestPlugin.swift
@@ -89,6 +89,18 @@ public class TestPlugin: NSObject, FlutterPlugin, HostIntegrationCoreApi {
     return anEnum
   }
 
+  func echoNamedDefault(_ aString: String) throws -> String {
+    return aString
+  }
+
+  func echoOptionalDefault(_ aDouble: Double) throws -> Double {
+    return aDouble
+  }
+
+  func echoRequired(_ anInt: Int64) throws -> Int64 {
+    return anInt
+  }
+
   func extractNestedNullableString(from wrapper: AllClassesWrapper) -> String? {
     return wrapper.allNullableTypes.aNullableString;
   }
@@ -138,6 +150,14 @@ public class TestPlugin: NSObject, FlutterPlugin, HostIntegrationCoreApi {
     return anEnum
   }
 
+  func echoOptional(_ aNullableInt: Int64?) throws -> Int64? {
+    return aNullableInt
+  }
+
+  func echoNamed(_ aNullableString: String?) throws -> String? {
+    return aNullableString
+  }
+
   func noopAsync(completion: @escaping (Result<Void, Error>) -> Void) {
     completion(.success(Void()))
   }
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp
index 6acd3cb1866..2ca7340b0ce 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp
+++ b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.cpp
@@ -1250,6 +1250,112 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
       channel->SetMessageHandler(nullptr);
     }
   }
+  {
+    auto channel = std::make_unique<BasicMessageChannel<>>(
+        binary_messenger,
+        "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+        "echoNamedDefaultString",
+        &GetCodec());
+    if (api != nullptr) {
+      channel->SetMessageHandler(
+          [api](const EncodableValue& message,
+                const flutter::MessageReply<EncodableValue>& reply) {
+            try {
+              const auto& args = std::get<EncodableList>(message);
+              const auto& encodable_a_string_arg = args.at(0);
+              if (encodable_a_string_arg.IsNull()) {
+                reply(WrapError("a_string_arg unexpectedly null."));
+                return;
+              }
+              const auto& a_string_arg =
+                  std::get<std::string>(encodable_a_string_arg);
+              ErrorOr<std::string> output =
+                  api->EchoNamedDefaultString(a_string_arg);
+              if (output.has_error()) {
+                reply(WrapError(output.error()));
+                return;
+              }
+              EncodableList wrapped;
+              wrapped.push_back(EncodableValue(std::move(output).TakeValue()));
+              reply(EncodableValue(std::move(wrapped)));
+            } catch (const std::exception& exception) {
+              reply(WrapError(exception.what()));
+            }
+          });
+    } else {
+      channel->SetMessageHandler(nullptr);
+    }
+  }
+  {
+    auto channel = std::make_unique<BasicMessageChannel<>>(
+        binary_messenger,
+        "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+        "echoOptionalDefaultDouble",
+        &GetCodec());
+    if (api != nullptr) {
+      channel->SetMessageHandler(
+          [api](const EncodableValue& message,
+                const flutter::MessageReply<EncodableValue>& reply) {
+            try {
+              const auto& args = std::get<EncodableList>(message);
+              const auto& encodable_a_double_arg = args.at(0);
+              if (encodable_a_double_arg.IsNull()) {
+                reply(WrapError("a_double_arg unexpectedly null."));
+                return;
+              }
+              const auto& a_double_arg =
+                  std::get<double>(encodable_a_double_arg);
+              ErrorOr<double> output =
+                  api->EchoOptionalDefaultDouble(a_double_arg);
+              if (output.has_error()) {
+                reply(WrapError(output.error()));
+                return;
+              }
+              EncodableList wrapped;
+              wrapped.push_back(EncodableValue(std::move(output).TakeValue()));
+              reply(EncodableValue(std::move(wrapped)));
+            } catch (const std::exception& exception) {
+              reply(WrapError(exception.what()));
+            }
+          });
+    } else {
+      channel->SetMessageHandler(nullptr);
+    }
+  }
+  {
+    auto channel = std::make_unique<BasicMessageChannel<>>(
+        binary_messenger,
+        "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+        "echoRequiredInt",
+        &GetCodec());
+    if (api != nullptr) {
+      channel->SetMessageHandler(
+          [api](const EncodableValue& message,
+                const flutter::MessageReply<EncodableValue>& reply) {
+            try {
+              const auto& args = std::get<EncodableList>(message);
+              const auto& encodable_an_int_arg = args.at(0);
+              if (encodable_an_int_arg.IsNull()) {
+                reply(WrapError("an_int_arg unexpectedly null."));
+                return;
+              }
+              const int64_t an_int_arg = encodable_an_int_arg.LongValue();
+              ErrorOr<int64_t> output = api->EchoRequiredInt(an_int_arg);
+              if (output.has_error()) {
+                reply(WrapError(output.error()));
+                return;
+              }
+              EncodableList wrapped;
+              wrapped.push_back(EncodableValue(std::move(output).TakeValue()));
+              reply(EncodableValue(std::move(wrapped)));
+            } catch (const std::exception& exception) {
+              reply(WrapError(exception.what()));
+            }
+          });
+    } else {
+      channel->SetMessageHandler(nullptr);
+    }
+  }
   {
     auto channel = std::make_unique<BasicMessageChannel<>>(
         binary_messenger,
@@ -1767,6 +1873,88 @@ void HostIntegrationCoreApi::SetUp(flutter::BinaryMessenger* binary_messenger,
       channel->SetMessageHandler(nullptr);
     }
   }
+  {
+    auto channel = std::make_unique<BasicMessageChannel<>>(
+        binary_messenger,
+        "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+        "echoOptionalNullableInt",
+        &GetCodec());
+    if (api != nullptr) {
+      channel->SetMessageHandler(
+          [api](const EncodableValue& message,
+                const flutter::MessageReply<EncodableValue>& reply) {
+            try {
+              const auto& args = std::get<EncodableList>(message);
+              const auto& encodable_a_nullable_int_arg = args.at(0);
+              const int64_t a_nullable_int_arg_value =
+                  encodable_a_nullable_int_arg.IsNull()
+                      ? 0
+                      : encodable_a_nullable_int_arg.LongValue();
+              const auto* a_nullable_int_arg =
+                  encodable_a_nullable_int_arg.IsNull()
+                      ? nullptr
+                      : &a_nullable_int_arg_value;
+              ErrorOr<std::optional<int64_t>> output =
+                  api->EchoOptionalNullableInt(a_nullable_int_arg);
+              if (output.has_error()) {
+                reply(WrapError(output.error()));
+                return;
+              }
+              EncodableList wrapped;
+              auto output_optional = std::move(output).TakeValue();
+              if (output_optional) {
+                wrapped.push_back(
+                    EncodableValue(std::move(output_optional).value()));
+              } else {
+                wrapped.push_back(EncodableValue());
+              }
+              reply(EncodableValue(std::move(wrapped)));
+            } catch (const std::exception& exception) {
+              reply(WrapError(exception.what()));
+            }
+          });
+    } else {
+      channel->SetMessageHandler(nullptr);
+    }
+  }
+  {
+    auto channel = std::make_unique<BasicMessageChannel<>>(
+        binary_messenger,
+        "dev.flutter.pigeon.pigeon_integration_tests.HostIntegrationCoreApi."
+        "echoNamedNullableString",
+        &GetCodec());
+    if (api != nullptr) {
+      channel->SetMessageHandler(
+          [api](const EncodableValue& message,
+                const flutter::MessageReply<EncodableValue>& reply) {
+            try {
+              const auto& args = std::get<EncodableList>(message);
+              const auto& encodable_a_nullable_string_arg = args.at(0);
+              const auto* a_nullable_string_arg =
+                  std::get_if<std::string>(&encodable_a_nullable_string_arg);
+              ErrorOr<std::optional<std::string>> output =
+                  api->EchoNamedNullableString(a_nullable_string_arg);
+              if (output.has_error()) {
+                reply(WrapError(output.error()));
+                return;
+              }
+              EncodableList wrapped;
+              auto output_optional = std::move(output).TakeValue();
+              if (output_optional) {
+                wrapped.push_back(
+                    EncodableValue(std::move(output_optional).value()));
+              } else {
+                wrapped.push_back(EncodableValue());
+              }
+              reply(EncodableValue(std::move(wrapped)));
+            } catch (const std::exception& exception) {
+              reply(WrapError(exception.what()));
+            }
+          });
+    } else {
+      channel->SetMessageHandler(nullptr);
+    }
+  }
   {
     auto channel = std::make_unique<BasicMessageChannel<>>(
         binary_messenger,
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
index b579f9fa87e..53c3320b3cf 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
+++ b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
@@ -414,6 +414,13 @@ class HostIntegrationCoreApi {
       const AllClassesWrapper& wrapper) = 0;
   // Returns the passed enum to test serialization and deserialization.
   virtual ErrorOr<AnEnum> EchoEnum(const AnEnum& an_enum) = 0;
+  // Returns the default string.
+  virtual ErrorOr<std::string> EchoNamedDefaultString(
+      const std::string& a_string) = 0;
+  // Returns passed in double.
+  virtual ErrorOr<double> EchoOptionalDefaultDouble(double a_double) = 0;
+  // Returns passed in int.
+  virtual ErrorOr<int64_t> EchoRequiredInt(int64_t an_int) = 0;
   // Returns the passed object, to test serialization and deserialization.
   virtual ErrorOr<std::optional<AllNullableTypes>> EchoAllNullableTypes(
       const AllNullableTypes* everything) = 0;
@@ -455,6 +462,12 @@ class HostIntegrationCoreApi {
       const flutter::EncodableMap* a_nullable_map) = 0;
   virtual ErrorOr<std::optional<AnEnum>> EchoNullableEnum(
       const AnEnum* an_enum) = 0;
+  // Returns passed in int.
+  virtual ErrorOr<std::optional<int64_t>> EchoOptionalNullableInt(
+      const int64_t* a_nullable_int) = 0;
+  // Returns the passed in string.
+  virtual ErrorOr<std::optional<std::string>> EchoNamedNullableString(
+      const std::string* a_nullable_string) = 0;
   // A no-op function taking no arguments and returning no value, to sanity
   // test basic asynchronous calling.
   virtual void NoopAsync(
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.cpp b/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.cpp
index ea71a076344..46535b3be80 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.cpp
+++ b/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.cpp
@@ -106,6 +106,17 @@ ErrorOr<AllClassesWrapper> TestPlugin::EchoClassWrapper(
 
 ErrorOr<AnEnum> TestPlugin::EchoEnum(const AnEnum& an_enum) { return an_enum; }
 
+ErrorOr<std::string> TestPlugin::EchoNamedDefaultString(
+    const std::string& a_string) {
+  return a_string;
+}
+
+ErrorOr<double> TestPlugin::EchoOptionalDefaultDouble(double a_double) {
+  return a_double;
+}
+
+ErrorOr<int64_t> TestPlugin::EchoRequiredInt(int64_t an_int) { return an_int; }
+
 ErrorOr<std::optional<std::string>> TestPlugin::ExtractNestedNullableString(
     const AllClassesWrapper& wrapper) {
   const std::string* inner_string =
@@ -218,6 +229,22 @@ ErrorOr<std::optional<AnEnum>> TestPlugin::EchoNullableEnum(
   return *an_enum;
 }
 
+ErrorOr<std::optional<int64_t>> TestPlugin::EchoOptionalNullableInt(
+    const int64_t* a_nullable_int) {
+  if (!a_nullable_int) {
+    return std::nullopt;
+  }
+  return *a_nullable_int;
+}
+
+ErrorOr<std::optional<std::string>> TestPlugin::EchoNamedNullableString(
+    const std::string* a_nullable_string) {
+  if (!a_nullable_string) {
+    return std::nullopt;
+  }
+  return *a_nullable_string;
+}
+
 void TestPlugin::NoopAsync(
     std::function<void(std::optional<FlutterError> reply)> result) {
   result(std::nullopt);
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.h b/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.h
index d66a8e5836a..e9fd9c6f2de 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.h
+++ b/packages/pigeon/platform_tests/test_plugin/windows/test_plugin.h
@@ -63,6 +63,12 @@ class TestPlugin : public flutter::Plugin,
       const core_tests_pigeontest::AllClassesWrapper& wrapper) override;
   core_tests_pigeontest::ErrorOr<core_tests_pigeontest::AnEnum> EchoEnum(
       const core_tests_pigeontest::AnEnum& an_enum) override;
+  core_tests_pigeontest::ErrorOr<std::string> EchoNamedDefaultString(
+      const std::string& a_string) override;
+  core_tests_pigeontest::ErrorOr<double> EchoOptionalDefaultDouble(
+      double a_double) override;
+  core_tests_pigeontest::ErrorOr<int64_t> EchoRequiredInt(
+      int64_t an_int) override;
   core_tests_pigeontest::ErrorOr<std::optional<std::string>>
   ExtractNestedNullableString(
       const core_tests_pigeontest::AllClassesWrapper& wrapper) override;
@@ -91,6 +97,10 @@ class TestPlugin : public flutter::Plugin,
   EchoNullableMap(const flutter::EncodableMap* a_nullable_map) override;
   core_tests_pigeontest::ErrorOr<std::optional<core_tests_pigeontest::AnEnum>>
   EchoNullableEnum(const core_tests_pigeontest::AnEnum* an_enum) override;
+  core_tests_pigeontest::ErrorOr<std::optional<int64_t>>
+  EchoOptionalNullableInt(const int64_t* a_nullable_int) override;
+  core_tests_pigeontest::ErrorOr<std::optional<std::string>>
+  EchoNamedNullableString(const std::string* a_nullable_string) override;
   void NoopAsync(std::function<
                  void(std::optional<core_tests_pigeontest::FlutterError> reply)>
                      result) override;
diff --git a/packages/pigeon/pubspec.yaml b/packages/pigeon/pubspec.yaml
index e4d61388375..c20492d9dc0 100644
--- a/packages/pigeon/pubspec.yaml
+++ b/packages/pigeon/pubspec.yaml
@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3Apigeon
-version: 13.1.2 # This must match the version in lib/generator_tools.dart
+version: 14.0.0 # This must match the version in lib/generator_tools.dart
 
 environment:
   sdk: ">=2.19.0 <4.0.0"
diff --git a/packages/pigeon/test/ast_generator_test.dart b/packages/pigeon/test/ast_generator_test.dart
index 0718c94895c..01cf75beafd 100644
--- a/packages/pigeon/test/ast_generator_test.dart
+++ b/packages/pigeon/test/ast_generator_test.dart
@@ -8,7 +8,7 @@ import 'package:test/test.dart';
 
 void main() {
   test('gen one class', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -21,7 +21,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
diff --git a/packages/pigeon/test/cpp_generator_test.dart b/packages/pigeon/test/cpp_generator_test.dart
index be426c1c395..cbd290b42fa 100644
--- a/packages/pigeon/test/cpp_generator_test.dart
+++ b/packages/pigeon/test/cpp_generator_test.dart
@@ -10,22 +10,38 @@ import 'package:test/test.dart';
 
 const String DEFAULT_PACKAGE_NAME = 'test_package';
 
+final Class emptyClass = Class(name: 'className', fields: <NamedType>[
+  NamedType(
+    name: 'namedTypeName',
+    type: const TypeDeclaration(baseName: 'baseName', isNullable: false),
+  )
+]);
+
+final Enum emptyEnum = Enum(
+  name: 'enumName',
+  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
+);
+
 void main() {
   test('gen one api', () {
     final Root root = Root(apis: <Api>[
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: 'input')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -88,16 +104,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: 'someInput')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -162,8 +182,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: false,
@@ -213,8 +233,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: false,
@@ -256,16 +276,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: 'input')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -329,8 +353,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: true,
@@ -402,8 +426,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: true,
@@ -457,11 +481,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: 'someInput')
           ],
@@ -497,9 +522,10 @@ void main() {
             ),
             name: 'nullableString'),
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Nested',
               isNullable: true,
+              associatedClass: emptyClass,
             ),
             name: 'nullableNested'),
       ]),
@@ -638,11 +664,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: 'someInput')
           ],
@@ -678,9 +705,10 @@ void main() {
             ),
             name: 'nonNullableString'),
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Nested',
               isNullable: false,
+              associatedClass: emptyClass,
             ),
             name: 'nonNullableNested'),
       ]),
@@ -779,7 +807,7 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'returnNullableBool',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'bool',
             isNullable: true,
@@ -787,7 +815,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableInt',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'int',
             isNullable: true,
@@ -795,7 +823,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableString',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'String',
             isNullable: true,
@@ -803,7 +831,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableList',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'List',
             typeArguments: <TypeDeclaration>[
@@ -817,7 +845,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableMap',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'Map',
             typeArguments: <TypeDeclaration>[
@@ -835,10 +863,11 @@ void main() {
         ),
         Method(
           name: 'returnNullableDataClass',
-          arguments: <NamedType>[],
-          returnType: const TypeDeclaration(
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
             baseName: 'ReturnData',
             isNullable: true,
+            associatedClass: emptyClass,
           ),
         ),
       ])
@@ -895,7 +924,7 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'returnBool',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'bool',
             isNullable: false,
@@ -903,7 +932,7 @@ void main() {
         ),
         Method(
           name: 'returnInt',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'int',
             isNullable: false,
@@ -911,7 +940,7 @@ void main() {
         ),
         Method(
           name: 'returnString',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'String',
             isNullable: false,
@@ -919,7 +948,7 @@ void main() {
         ),
         Method(
           name: 'returnList',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'List',
             typeArguments: <TypeDeclaration>[
@@ -933,7 +962,7 @@ void main() {
         ),
         Method(
           name: 'returnMap',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'Map',
             typeArguments: <TypeDeclaration>[
@@ -951,10 +980,11 @@ void main() {
         ),
         Method(
           name: 'returnDataClass',
-          arguments: <NamedType>[],
-          returnType: const TypeDeclaration(
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
             baseName: 'ReturnData',
             isNullable: false,
+            associatedClass: emptyClass,
           ),
         ),
       ])
@@ -997,26 +1027,26 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'aBool',
                 type: const TypeDeclaration(
                   baseName: 'bool',
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anInt',
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aString',
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aList',
                 type: const TypeDeclaration(
                   baseName: 'List',
@@ -1025,7 +1055,7 @@ void main() {
                   ],
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aMap',
                 type: const TypeDeclaration(
                   baseName: 'Map',
@@ -1035,13 +1065,14 @@ void main() {
                   ],
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anObject',
-                type: const TypeDeclaration(
+                type: TypeDeclaration(
                   baseName: 'ParameterObject',
                   isNullable: true,
+                  associatedClass: emptyClass,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aGenericObject',
                 type: const TypeDeclaration(
                   baseName: 'Object',
@@ -1123,7 +1154,7 @@ void main() {
           contains(
               'const auto* a_map_arg = std::get_if<EncodableMap>(&encodable_a_map_arg);'));
       // Ints are complicated since there are two possible pointer types, but
-      // the paramter always needs an int64_t*.
+      // the parameter always needs an int64_t*.
       expect(
           code,
           contains(
@@ -1151,26 +1182,26 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'aBool',
                 type: const TypeDeclaration(
                   baseName: 'bool',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anInt',
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aString',
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aList',
                 type: const TypeDeclaration(
                   baseName: 'List',
@@ -1179,7 +1210,7 @@ void main() {
                   ],
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aMap',
                 type: const TypeDeclaration(
                   baseName: 'Map',
@@ -1189,13 +1220,14 @@ void main() {
                   ],
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anObject',
-                type: const TypeDeclaration(
+                type: TypeDeclaration(
                   baseName: 'ParameterObject',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aGenericObject',
                 type: const TypeDeclaration(
                   baseName: 'Object',
@@ -1275,7 +1307,7 @@ void main() {
           contains(
               'const auto& a_map_arg = std::get<EncodableMap>(encodable_a_map_arg);'));
       // Ints use a copy since there are two possible reference types, but
-      // the paramter always needs an int64_t.
+      // the parameter always needs an int64_t.
       expect(
           code,
           contains(
@@ -1300,26 +1332,26 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'aBool',
                 type: const TypeDeclaration(
                   baseName: 'bool',
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anInt',
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aString',
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aList',
                 type: const TypeDeclaration(
                   baseName: 'List',
@@ -1328,7 +1360,7 @@ void main() {
                   ],
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aMap',
                 type: const TypeDeclaration(
                   baseName: 'Map',
@@ -1338,13 +1370,14 @@ void main() {
                   ],
                   isNullable: true,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anObject',
-                type: const TypeDeclaration(
+                type: TypeDeclaration(
                   baseName: 'ParameterObject',
                   isNullable: true,
+                  associatedClass: emptyClass,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aGenericObject',
                 type: const TypeDeclaration(
                   baseName: 'Object',
@@ -1458,26 +1491,26 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'aBool',
                 type: const TypeDeclaration(
                   baseName: 'bool',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anInt',
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aString',
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aList',
                 type: const TypeDeclaration(
                   baseName: 'List',
@@ -1486,7 +1519,7 @@ void main() {
                   ],
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aMap',
                 type: const TypeDeclaration(
                   baseName: 'Map',
@@ -1496,13 +1529,14 @@ void main() {
                   ],
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anObject',
-                type: const TypeDeclaration(
+                type: TypeDeclaration(
                   baseName: 'ParameterObject',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aGenericObject',
                 type: const TypeDeclaration(
                   baseName: 'Object',
@@ -1590,8 +1624,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'anArg',
                 type: const TypeDeclaration(
                   baseName: 'int',
@@ -1618,7 +1652,7 @@ void main() {
     );
     final String code = sink.toString();
     // A bare 'auto' here would create a copy, not a reference, which is
-    // ineffecient.
+    // inefficient.
     expect(
         code, contains('const auto& args = std::get<EncodableList>(message);'));
     expect(code, contains('const auto& encodable_an_arg_arg = args.at(0);'));
@@ -1631,11 +1665,15 @@ void main() {
           Method(
               name: 'bar',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
-                    name: 'foo',
-                    type: const TypeDeclaration(
-                        baseName: 'Foo', isNullable: false))
+              parameters: <Parameter>[
+                Parameter(
+                  name: 'foo',
+                  type: TypeDeclaration(
+                    baseName: 'Foo',
+                    isNullable: false,
+                    associatedEnum: emptyEnum,
+                  ),
+                )
               ])
         ])
       ],
@@ -1676,8 +1714,8 @@ void main() {
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1744,7 +1782,7 @@ void main() {
     expect(code, contains('// ///'));
   });
 
-  test('doesnt create codecs if no custom datatypes', () {
+  test("doesn't create codecs if no custom datatypes", () {
     final Root root = Root(
       apis: <Api>[
         Api(
@@ -1754,8 +1792,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1792,16 +1830,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -1845,26 +1887,26 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'aBool',
                 type: const TypeDeclaration(
                   baseName: 'bool',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anInt',
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aString',
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aList',
                 type: const TypeDeclaration(
                   baseName: 'List',
@@ -1873,7 +1915,7 @@ void main() {
                   ],
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'aMap',
                 type: const TypeDeclaration(
                   baseName: 'Map',
@@ -1883,11 +1925,12 @@ void main() {
                   ],
                   isNullable: false,
                 )),
-            NamedType(
+            Parameter(
                 name: 'anObject',
-                type: const TypeDeclaration(
+                type: TypeDeclaration(
                   baseName: 'ParameterObject',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 )),
           ],
           returnType: const TypeDeclaration.voidDeclaration(),
@@ -1926,14 +1969,14 @@ void main() {
       Api(name: 'HostApi', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'noop',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration.voidDeclaration(),
           isAsynchronous: true,
         ),
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: false,
@@ -1948,14 +1991,14 @@ void main() {
       Api(name: 'FlutterApi', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'noop',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType: const TypeDeclaration.voidDeclaration(),
           isAsynchronous: true,
         ),
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: false,
@@ -2002,8 +2045,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
diff --git a/packages/pigeon/test/dart_generator_test.dart b/packages/pigeon/test/dart_generator_test.dart
index fdf9c1d1b87..2ab5f3f8df0 100644
--- a/packages/pigeon/test/dart_generator_test.dart
+++ b/packages/pigeon/test/dart_generator_test.dart
@@ -12,22 +12,35 @@ import 'package:test/test.dart';
 
 const String DEFAULT_PACKAGE_NAME = 'test_package';
 
+final Class emptyClass = Class(name: 'className', fields: <NamedType>[
+  NamedType(
+    name: 'namedTypeName',
+    type: const TypeDeclaration(baseName: 'baseName', isNullable: false),
+  )
+]);
+
+final Enum emptyEnum = Enum(
+  name: 'enumName',
+  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
+);
+
 void main() {
   test('gen one class', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'dataType1',
               isNullable: true,
+              associatedClass: emptyClass,
             ),
             name: 'field1'),
       ],
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -75,16 +88,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: 'input')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -115,7 +132,7 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('class Api'));
-    expect(code, contains('Future<Output> doSomething(Input arg_input)'));
+    expect(code, contains('Future<Output> doSomething(Input input)'));
   });
 
   test('host multiple args', () {
@@ -123,12 +140,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -147,8 +164,8 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('class Api'));
-    expect(code, contains('Future<int> add(int arg_x, int arg_y)'));
-    expect(code, contains('await channel.send(<Object?>[arg_x, arg_y])'));
+    expect(code, contains('Future<int> add(int x, int y)'));
+    expect(code, contains('await __pigeon_channel.send(<Object?>[x, y])'));
   });
 
   test('flutter multiple args', () {
@@ -156,12 +173,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -205,9 +222,10 @@ void main() {
         name: 'Nested',
         fields: <NamedType>[
           NamedType(
-              type: const TypeDeclaration(
+              type: TypeDeclaration(
                 baseName: 'Input',
                 isNullable: true,
+                associatedClass: emptyClass,
               ),
               name: 'nested')
         ],
@@ -253,9 +271,10 @@ void main() {
         name: 'Nested',
         fields: <NamedType>[
           NamedType(
-              type: const TypeDeclaration(
+              type: TypeDeclaration(
                 baseName: 'Input',
                 isNullable: false,
+                associatedClass: emptyClass,
               ),
               name: 'nested')
         ],
@@ -289,16 +308,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: 'input')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -338,11 +361,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: '')
           ],
@@ -377,11 +401,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: '')
           ],
@@ -419,9 +444,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -452,24 +480,29 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'EnumClass',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
-                name: '')
+                name: 'enumClass')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'EnumClass', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'EnumClass',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
       Class(name: 'EnumClass', fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Enum',
               isNullable: true,
+              associatedEnum: emptyEnum,
             ),
             name: 'enum1')
       ]),
@@ -493,7 +526,7 @@ void main() {
     final String code = sink.toString();
     expect(code, contains('enum1?.index,'));
     expect(code, contains('? Enum.values[result[0]! as int]'));
-    expect(code, contains('EnumClass doSomething(EnumClass arg0);'));
+    expect(code, contains('EnumClass doSomething(EnumClass enumClass);'));
   });
 
   test('primitive enum host', () {
@@ -502,11 +535,14 @@ void main() {
         Method(
             name: 'bar',
             returnType: const TypeDeclaration.voidDeclaration(),
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'foo',
-                  type:
-                      const TypeDeclaration(baseName: 'Foo', isNullable: true))
+                  type: TypeDeclaration(
+                    baseName: 'Foo',
+                    isNullable: true,
+                    associatedEnum: emptyEnum,
+                  ))
             ])
       ])
     ], classes: <Class>[], enums: <Enum>[
@@ -525,8 +561,8 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('enum Foo {'));
-    expect(code, contains('Future<void> bar(Foo? arg_foo) async'));
-    expect(code, contains('channel.send(<Object?>[arg_foo?.index])'));
+    expect(code, contains('Future<void> bar(Foo? foo) async'));
+    expect(code, contains('__pigeon_channel.send(<Object?>[foo?.index])'));
   });
 
   test('flutter non-nullable enum argument with enum class', () {
@@ -534,24 +570,29 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'EnumClass',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'EnumClass', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'EnumClass',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
       Class(name: 'EnumClass', fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Enum',
               isNullable: false,
+              associatedEnum: emptyEnum,
             ),
             name: 'enum1')
       ]),
@@ -582,9 +623,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -606,7 +650,7 @@ void main() {
       dartPackageName: DEFAULT_PACKAGE_NAME,
     );
     final String code = sink.toString();
-    expect(code, matches('channel.send[(]null[)]'));
+    expect(code, matches('__pigeon_channel.send[(]null[)]'));
   });
 
   test('mock dart handler', () {
@@ -618,24 +662,29 @@ void main() {
           methods: <Method>[
             Method(
               name: 'doSomething',
-              arguments: <NamedType>[
-                NamedType(
-                    type: const TypeDeclaration(
+              parameters: <Parameter>[
+                Parameter(
+                    type: TypeDeclaration(
                       baseName: 'Input',
                       isNullable: false,
+                      associatedClass: emptyClass,
                     ),
                     name: '')
               ],
-              returnType:
-                  const TypeDeclaration(baseName: 'Output', isNullable: false),
+              returnType: TypeDeclaration(
+                baseName: 'Output',
+                isNullable: false,
+                associatedClass: emptyClass,
+              ),
             ),
             Method(
               name: 'voidReturner',
-              arguments: <NamedType>[
-                NamedType(
-                    type: const TypeDeclaration(
+              parameters: <Parameter>[
+                Parameter(
+                    type: TypeDeclaration(
                       baseName: 'Input',
                       isNullable: false,
+                      associatedClass: emptyClass,
                     ),
                     name: '')
               ],
@@ -702,16 +751,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
-                name: '')
+                name: 'input')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -743,9 +796,9 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('abstract class Api'));
-    expect(code, contains('Future<Output> doSomething(Input arg0);'));
-    expect(
-        code, contains('final Output output = await api.doSomething(arg0!);'));
+    expect(code, contains('Future<Output> doSomething(Input input);'));
+    expect(code,
+        contains('final Output output = await api.doSomething(arg_input!);'));
   });
 
   test('gen one async Flutter Api with void return', () {
@@ -753,11 +806,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: '')
           ],
@@ -802,16 +856,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -851,9 +909,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -876,7 +937,7 @@ void main() {
       dartPackageName: DEFAULT_PACKAGE_NAME,
     );
     final String code = sink.toString();
-    expect(code, matches('channel.send[(]null[)]'));
+    expect(code, matches('__pigeon_channel.send[(]null[)]'));
   });
 
   Iterable<String> makeIterable(String string) sync* {
@@ -899,7 +960,7 @@ void main() {
   });
 
   test('generics', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -914,7 +975,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -931,7 +992,7 @@ void main() {
   });
 
   test('map generics', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -947,7 +1008,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -970,8 +1031,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -1004,8 +1065,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -1043,7 +1104,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1059,8 +1120,10 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('Future<List<int?>> doit('));
-    expect(code,
-        contains('return (replyList[0] as List<Object?>?)!.cast<int?>();'));
+    expect(
+        code,
+        contains(
+            'return (__pigeon_replyList[0] as List<Object?>?)!.cast<int?>();'));
   });
 
   test('flutter generics argument non void return', () {
@@ -1075,8 +1138,8 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -1117,7 +1180,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1133,7 +1196,7 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('Future<int?> doit()'));
-    expect(code, contains('return (replyList[0] as int?);'));
+    expect(code, contains('return (__pigeon_replyList[0] as int?);'));
   });
 
   test('return nullable collection host', () {
@@ -1148,7 +1211,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1164,8 +1227,10 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('Future<List<int?>?> doit()'));
-    expect(code,
-        contains('return (replyList[0] as List<Object?>?)?.cast<int?>();'));
+    expect(
+        code,
+        contains(
+            'return (__pigeon_replyList[0] as List<Object?>?)?.cast<int?>();'));
   });
 
   test('return nullable async host', () {
@@ -1178,7 +1243,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[],
+              parameters: <Parameter>[],
               isAsynchronous: true)
         ])
       ],
@@ -1195,7 +1260,7 @@ void main() {
     );
     final String code = sink.toString();
     expect(code, contains('Future<int?> doit()'));
-    expect(code, contains('return (replyList[0] as int?);'));
+    expect(code, contains('return (__pigeon_replyList[0] as int?);'));
   });
 
   test('return nullable flutter', () {
@@ -1208,7 +1273,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1237,7 +1302,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[],
+              parameters: <Parameter>[],
               isAsynchronous: true)
         ])
       ],
@@ -1267,7 +1332,7 @@ void main() {
                 baseName: 'int',
                 isNullable: false,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1295,8 +1360,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1317,7 +1382,7 @@ void main() {
       dartPackageName: DEFAULT_PACKAGE_NAME,
     );
     final String code = sink.toString();
-    expect(code, contains('Future<void> doit(int? arg_foo) async {'));
+    expect(code, contains('Future<void> doit(int? foo) async {'));
   });
 
   test('nullable argument flutter', () {
@@ -1327,8 +1392,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1411,8 +1476,8 @@ name: foobar
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1484,8 +1549,8 @@ name: foobar
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1518,16 +1583,20 @@ name: foobar
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
                   isNullable: false,
+                  associatedClass: emptyClass,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -1572,11 +1641,12 @@ name: foobar
               Method(
                   name: 'doit',
                   returnType: const TypeDeclaration.voidDeclaration(),
-                  arguments: <NamedType>[
-                    NamedType(
-                        type: const TypeDeclaration(
+                  parameters: <Parameter>[
+                    Parameter(
+                        type: TypeDeclaration(
                           baseName: 'Enum',
                           isNullable: false,
+                          associatedEnum: emptyEnum,
                         ),
                         name: 'anEnum')
                   ])
@@ -1619,7 +1689,7 @@ name: foobar
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'method',
-          arguments: <NamedType>[],
+          parameters: <Parameter>[],
           returnType:
               const TypeDeclaration(baseName: 'Output', isNullable: false),
         )
@@ -1634,7 +1704,8 @@ name: foobar
       dartPackageName: DEFAULT_PACKAGE_NAME,
     );
     final String code = sink.toString();
-    expect(code, contains('throw _createConnectionError(channelName);'));
+    expect(
+        code, contains('throw _createConnectionError(__pigeon_channelName);'));
     expect(
         code,
         contains(
diff --git a/packages/pigeon/test/generator_tools_test.dart b/packages/pigeon/test/generator_tools_test.dart
index 82b23ae1c5e..4570ac633aa 100644
--- a/packages/pigeon/test/generator_tools_test.dart
+++ b/packages/pigeon/test/generator_tools_test.dart
@@ -37,6 +37,18 @@ bool _equalMaps(Map<String, Object> x, Map<String, Object> y) {
   return true;
 }
 
+final Class emptyClass = Class(name: 'className', fields: <NamedType>[
+  NamedType(
+    name: 'namedTypeName',
+    type: const TypeDeclaration(baseName: 'baseName', isNullable: false),
+  )
+]);
+
+final Enum emptyEnum = Enum(
+  name: 'enumName',
+  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
+);
+
 void main() {
   test('test merge maps', () {
     final Map<String, Object> source = <String, Object>{
@@ -70,20 +82,27 @@ void main() {
         Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
       Method(
         name: 'doSomething',
-        arguments: <NamedType>[
-          NamedType(
-            type: const TypeDeclaration(
+        parameters: <Parameter>[
+          Parameter(
+            type: TypeDeclaration(
               baseName: 'List',
               isNullable: false,
               typeArguments: <TypeDeclaration>[
-                TypeDeclaration(baseName: 'Input', isNullable: true)
+                TypeDeclaration(
+                  baseName: 'Input',
+                  isNullable: true,
+                  associatedClass: emptyClass,
+                )
               ],
             ),
             name: '',
           )
         ],
-        returnType:
-            const TypeDeclaration(baseName: 'Output', isNullable: false),
+        returnType: TypeDeclaration(
+          baseName: 'Output',
+          isNullable: false,
+          associatedClass: emptyClass,
+        ),
         isAsynchronous: true,
       )
     ]);
@@ -108,17 +127,25 @@ void main() {
         Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
       Method(
         name: 'doSomething',
-        arguments: <NamedType>[
-          NamedType(
-            type: const TypeDeclaration(baseName: 'Output', isNullable: false),
+        parameters: <Parameter>[
+          Parameter(
+            type: TypeDeclaration(
+              baseName: 'Output',
+              isNullable: false,
+              associatedClass: emptyClass,
+            ),
             name: '',
           )
         ],
-        returnType: const TypeDeclaration(
+        returnType: TypeDeclaration(
           baseName: 'List',
           isNullable: false,
           typeArguments: <TypeDeclaration>[
-            TypeDeclaration(baseName: 'Input', isNullable: true)
+            TypeDeclaration(
+              baseName: 'Input',
+              isNullable: true,
+              associatedClass: emptyClass,
+            )
           ],
         ),
         isAsynchronous: true,
@@ -145,13 +172,21 @@ void main() {
         Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
       Method(
         name: 'doSomething',
-        arguments: <NamedType>[
-          NamedType(
-            type: const TypeDeclaration(baseName: 'Foo', isNullable: false),
+        parameters: <Parameter>[
+          Parameter(
+            type: TypeDeclaration(
+              baseName: 'Foo',
+              isNullable: false,
+              associatedClass: emptyClass,
+            ),
             name: '',
           ),
-          NamedType(
-            type: const TypeDeclaration(baseName: 'Bar', isNullable: false),
+          Parameter(
+            type: TypeDeclaration(
+              baseName: 'Bar',
+              isNullable: false,
+              associatedEnum: emptyEnum,
+            ),
             name: '',
           ),
         ],
@@ -184,14 +219,18 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'foo',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
-                type: const TypeDeclaration(
+                type: TypeDeclaration(
                     isNullable: false,
                     baseName: 'List',
                     typeArguments: <TypeDeclaration>[
-                      TypeDeclaration(baseName: 'Foo', isNullable: true)
+                      TypeDeclaration(
+                        baseName: 'Foo',
+                        isNullable: true,
+                        associatedClass: emptyClass,
+                      )
                     ])),
           ],
           returnType: const TypeDeclaration.voidDeclaration(),
@@ -201,12 +240,19 @@ void main() {
       Class(name: 'Foo', fields: <NamedType>[
         NamedType(
             name: 'bar',
-            type: const TypeDeclaration(baseName: 'Bar', isNullable: true)),
+            type: TypeDeclaration(
+              baseName: 'Bar',
+              isNullable: true,
+              associatedClass: emptyClass,
+            )),
       ]),
       Class(name: 'Bar', fields: <NamedType>[
         NamedType(
             name: 'value',
-            type: const TypeDeclaration(baseName: 'int', isNullable: true))
+            type: const TypeDeclaration(
+              baseName: 'int',
+              isNullable: true,
+            ))
       ])
     ], enums: <Enum>[]);
     final List<EnumeratedClass> classes =
@@ -232,8 +278,8 @@ void main() {
         methods: <Method>[
           Method(
             name: 'foo',
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'x',
                   type: const TypeDeclaration(
                       isNullable: false,
@@ -271,11 +317,14 @@ void main() {
         methods: <Method>[
           Method(
             name: 'foo',
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'x',
-                  type: const TypeDeclaration(
-                      isNullable: false, baseName: 'Foo')),
+                  type: TypeDeclaration(
+                    isNullable: false,
+                    baseName: 'Foo',
+                    associatedClass: emptyClass,
+                  )),
             ],
             returnType: const TypeDeclaration.voidDeclaration(),
           )
@@ -287,11 +336,14 @@ void main() {
         methods: <Method>[
           Method(
             name: 'foo',
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'x',
-                  type: const TypeDeclaration(
-                      isNullable: false, baseName: 'Foo')),
+                  type: TypeDeclaration(
+                    isNullable: false,
+                    baseName: 'Foo',
+                    associatedClass: emptyClass,
+                  )),
             ],
             returnType: const TypeDeclaration.voidDeclaration(),
           )
diff --git a/packages/pigeon/test/java_generator_test.dart b/packages/pigeon/test/java_generator_test.dart
index 15abd016a68..99936ca2b92 100644
--- a/packages/pigeon/test/java_generator_test.dart
+++ b/packages/pigeon/test/java_generator_test.dart
@@ -9,9 +9,21 @@ import 'package:test/test.dart';
 
 const String DEFAULT_PACKAGE_NAME = 'test_package';
 
+final Class emptyClass = Class(name: 'className', fields: <NamedType>[
+  NamedType(
+    name: 'namedTypeName',
+    type: const TypeDeclaration(baseName: 'baseName', isNullable: false),
+  )
+]);
+
+final Enum emptyEnum = Enum(
+  name: 'enumName',
+  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
+);
+
 void main() {
   test('gen one class', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -24,7 +36,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -77,7 +89,7 @@ void main() {
   });
 
   test('package', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -90,7 +102,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -113,16 +125,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -251,16 +267,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -300,10 +320,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
@@ -340,10 +361,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
@@ -383,9 +405,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -417,9 +442,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -498,12 +526,13 @@ void main() {
   });
 
   test('gen nested', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Outer',
       fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Nested',
+              associatedClass: emptyClass,
               isNullable: true,
             ),
             name: 'nested')
@@ -522,7 +551,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass, nestedClass],
+      classes: <Class>[classDefinition, nestedClass],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -551,16 +580,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: 'arg')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -608,16 +641,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -662,12 +699,13 @@ void main() {
         EnumMember(name: 'remoteDB'),
       ],
     );
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'EnumClass',
       fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Enum1',
+              associatedEnum: emptyEnum,
               isNullable: true,
             ),
             name: 'enum1'),
@@ -675,7 +713,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[anEnum],
     );
     final StringBuffer sink = StringBuffer();
@@ -710,11 +748,15 @@ void main() {
         Method(
             name: 'bar',
             returnType: const TypeDeclaration.voidDeclaration(),
-            arguments: <NamedType>[
-              NamedType(
-                  name: 'foo',
-                  type:
-                      const TypeDeclaration(baseName: 'Foo', isNullable: true))
+            parameters: <Parameter>[
+              Parameter(
+                name: 'foo',
+                type: TypeDeclaration(
+                  baseName: 'Foo',
+                  isNullable: true,
+                  associatedEnum: emptyEnum,
+                ),
+              )
             ])
       ])
     ], classes: <Class>[], enums: <Enum>[
@@ -763,7 +805,7 @@ void main() {
   });
 
   test('generics', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -778,7 +820,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -796,7 +838,7 @@ void main() {
   });
 
   test('generics - maps', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -812,7 +854,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -836,8 +878,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -871,8 +913,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -911,7 +953,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -943,7 +985,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -972,7 +1014,7 @@ void main() {
               name: 'doit',
               returnType:
                   const TypeDeclaration(baseName: 'int', isNullable: false),
-              arguments: <NamedType>[],
+              parameters: <Parameter>[],
               isAsynchronous: true)
         ])
       ],
@@ -1001,12 +1043,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -1042,8 +1084,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'objectTest',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type: const TypeDeclaration(
                     isNullable: false, baseName: 'Object')),
@@ -1070,12 +1112,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -1112,8 +1154,8 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'send',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -1148,7 +1190,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1178,7 +1220,7 @@ void main() {
                 isNullable: true,
               ),
               isAsynchronous: true,
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1205,8 +1247,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1238,8 +1280,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1274,8 +1316,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1309,13 +1351,13 @@ void main() {
   });
 
   test('generated annotation', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[],
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -1333,13 +1375,13 @@ void main() {
   });
 
   test('no generated annotation', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[],
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -1381,8 +1423,8 @@ void main() {
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1460,8 +1502,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1495,16 +1537,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -1570,8 +1616,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
diff --git a/packages/pigeon/test/kotlin_generator_test.dart b/packages/pigeon/test/kotlin_generator_test.dart
index 9f2fb321816..606f47e3690 100644
--- a/packages/pigeon/test/kotlin_generator_test.dart
+++ b/packages/pigeon/test/kotlin_generator_test.dart
@@ -8,9 +8,21 @@ import 'package:test/test.dart';
 
 const String DEFAULT_PACKAGE_NAME = 'test_package';
 
+final Class emptyClass = Class(name: 'className', fields: <NamedType>[
+  NamedType(
+    name: 'namedTypeName',
+    type: const TypeDeclaration(baseName: 'baseName', isNullable: false),
+  )
+]);
+
+final Enum emptyEnum = Enum(
+  name: 'enumName',
+  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
+);
+
 void main() {
   test('gen one class', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -24,7 +36,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -80,9 +92,10 @@ void main() {
           fields: <NamedType>[
             NamedType(
               name: 'field1',
-              type: const TypeDeclaration(
+              type: TypeDeclaration(
                 baseName: 'Foo',
                 isNullable: false,
+                associatedEnum: emptyEnum,
               ),
             ),
             NamedType(
@@ -131,11 +144,14 @@ void main() {
         Method(
             name: 'bar',
             returnType: const TypeDeclaration.voidDeclaration(),
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'foo',
-                  type:
-                      const TypeDeclaration(baseName: 'Foo', isNullable: false))
+                  type: TypeDeclaration(
+                    baseName: 'Foo',
+                    isNullable: false,
+                    associatedEnum: emptyEnum,
+                  ))
             ])
       ])
     ], classes: <Class>[], enums: <Enum>[
@@ -163,17 +179,21 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-              type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+              type: TypeDeclaration(
                 baseName: 'Input',
+                associatedClass: emptyClass,
                 isNullable: false,
               ),
               name: 'input',
             )
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -388,17 +408,21 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-              type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+              type: TypeDeclaration(
                 baseName: 'Input',
+                associatedClass: emptyClass,
                 isNullable: false,
               ),
               name: '',
             )
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -441,10 +465,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-              type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+              type: TypeDeclaration(
                 baseName: 'Input',
+                associatedClass: emptyClass,
                 isNullable: false,
               ),
               name: '',
@@ -483,10 +508,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-              type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+              type: TypeDeclaration(
                 baseName: 'Input',
+                associatedClass: emptyClass,
                 isNullable: false,
               ),
               name: '',
@@ -527,9 +553,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -564,9 +593,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -648,12 +680,13 @@ void main() {
   });
 
   test('gen nested', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Outer',
       fields: <NamedType>[
         NamedType(
-          type: const TypeDeclaration(
+          type: TypeDeclaration(
             baseName: 'Nested',
+            associatedClass: emptyClass,
             isNullable: true,
           ),
           name: 'nested',
@@ -674,7 +707,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass, nestedClass],
+      classes: <Class>[classDefinition, nestedClass],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -702,17 +735,21 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-              type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+              type: TypeDeclaration(
                 baseName: 'Input',
+                associatedClass: emptyClass,
                 isNullable: false,
               ),
               name: 'arg',
             )
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -756,17 +793,21 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-              type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+              type: TypeDeclaration(
                 baseName: 'Input',
+                associatedClass: emptyClass,
                 isNullable: false,
               ),
               name: '',
             )
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -812,12 +853,13 @@ void main() {
         EnumMember(name: 'two'),
       ],
     );
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'EnumClass',
       fields: <NamedType>[
         NamedType(
-          type: const TypeDeclaration(
+          type: TypeDeclaration(
             baseName: 'Enum1',
+            associatedEnum: emptyEnum,
             isNullable: true,
           ),
           name: 'enum1',
@@ -826,7 +868,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[anEnum],
     );
     final StringBuffer sink = StringBuffer();
@@ -866,7 +908,7 @@ void main() {
   });
 
   test('generics - list', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -882,7 +924,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -900,7 +942,7 @@ void main() {
   });
 
   test('generics - maps', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -917,7 +959,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -941,8 +983,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   type: const TypeDeclaration(
                       baseName: 'List',
                       isNullable: false,
@@ -977,8 +1019,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   type: const TypeDeclaration(
                       baseName: 'List',
                       isNullable: false,
@@ -1018,7 +1060,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1051,7 +1093,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1077,12 +1119,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -1120,12 +1162,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(baseName: 'int', isNullable: false)),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(baseName: 'int', isNullable: false)),
@@ -1168,7 +1210,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1198,7 +1240,7 @@ void main() {
                 isNullable: true,
               ),
               isAsynchronous: true,
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1224,8 +1266,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1260,8 +1302,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1294,10 +1336,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-              type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+              type: TypeDeclaration(
                 baseName: 'Input',
+                associatedClass: emptyClass,
                 isNullable: false,
               ),
               name: '',
@@ -1355,8 +1398,8 @@ void main() {
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1434,8 +1477,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1469,16 +1512,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -1517,7 +1564,7 @@ void main() {
     final Method method = Method(
         name: 'doSomething',
         returnType: const TypeDeclaration.voidDeclaration(),
-        arguments: <NamedType>[]);
+        parameters: <Parameter>[]);
     final Api api = Api(
         name: 'SomeApi', location: ApiLocation.host, methods: <Method>[method]);
     final Root root = Root(
@@ -1553,8 +1600,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
diff --git a/packages/pigeon/test/objc_generator_test.dart b/packages/pigeon/test/objc_generator_test.dart
index ef1d91f1f70..f77f186ac8d 100644
--- a/packages/pigeon/test/objc_generator_test.dart
+++ b/packages/pigeon/test/objc_generator_test.dart
@@ -10,6 +10,18 @@ import 'package:test/test.dart';
 
 const String DEFAULT_PACKAGE_NAME = 'test_package';
 
+final Class emptyClass = Class(name: 'className', fields: <NamedType>[
+  NamedType(
+    name: 'namedTypeName',
+    type: const TypeDeclaration(baseName: 'baseName', isNullable: false),
+  )
+]);
+
+final Enum emptyEnum = Enum(
+  name: 'enumName',
+  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
+);
+
 void main() {
   test('gen one class header', () {
     final Root root = Root(apis: <Api>[], classes: <Class>[
@@ -133,8 +145,11 @@ void main() {
                     const TypeDeclaration(baseName: 'String', isNullable: true),
                 name: 'field1'),
             NamedType(
-                type:
-                    const TypeDeclaration(baseName: 'Enum1', isNullable: true),
+                type: TypeDeclaration(
+                  baseName: 'Enum1',
+                  associatedEnum: emptyEnum,
+                  isNullable: true,
+                ),
                 name: 'enum1'),
           ],
         ),
@@ -177,11 +192,14 @@ void main() {
         Method(
             name: 'bar',
             returnType: const TypeDeclaration.voidDeclaration(),
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'foo',
-                  type:
-                      const TypeDeclaration(baseName: 'Foo', isNullable: false))
+                  type: TypeDeclaration(
+                    baseName: 'Foo',
+                    associatedEnum: emptyEnum,
+                    isNullable: false,
+                  ))
             ])
       ])
     ], classes: <Class>[], enums: <Enum>[
@@ -237,11 +255,14 @@ void main() {
         Method(
             name: 'bar',
             returnType: const TypeDeclaration.voidDeclaration(),
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'foo',
-                  type:
-                      const TypeDeclaration(baseName: 'Foo', isNullable: true))
+                  type: TypeDeclaration(
+                    baseName: 'Foo',
+                    associatedEnum: emptyEnum,
+                    isNullable: true,
+                  ))
             ])
       ])
     ], classes: <Class>[], enums: <Enum>[
@@ -268,8 +289,11 @@ void main() {
                     const TypeDeclaration(baseName: 'String', isNullable: true),
                 name: 'field1'),
             NamedType(
-                type:
-                    const TypeDeclaration(baseName: 'Enum1', isNullable: true),
+                type: TypeDeclaration(
+                  baseName: 'Enum1',
+                  associatedEnum: emptyEnum,
+                  isNullable: true,
+                ),
                 name: 'enum1'),
           ],
         ),
@@ -307,14 +331,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
-                      baseName: 'Input', isNullable: false),
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
+                    baseName: 'Input',
+                    associatedClass: emptyClass,
+                    isNullable: false,
+                  ),
                   name: '')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <NamedType>[
@@ -356,16 +386,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <NamedType>[
@@ -505,7 +539,11 @@ void main() {
       ]),
       Class(name: 'Nested', fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(baseName: 'Input', isNullable: true),
+            type: TypeDeclaration(
+              baseName: 'Input',
+              associatedClass: emptyClass,
+              isNullable: true,
+            ),
             name: 'nested')
       ])
     ], enums: <Enum>[]);
@@ -536,7 +574,11 @@ void main() {
       ]),
       Class(name: 'Nested', fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(baseName: 'Input', isNullable: true),
+            type: TypeDeclaration(
+              baseName: 'Input',
+              associatedClass: emptyClass,
+              isNullable: true,
+            ),
             name: 'nested')
       ])
     ], enums: <Enum>[]);
@@ -617,16 +659,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Nested', isNullable: false))
+            returnType: TypeDeclaration(
+              baseName: 'Nested',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <NamedType>[
@@ -636,7 +682,11 @@ void main() {
       ]),
       Class(name: 'Nested', fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(baseName: 'Input', isNullable: true),
+            type: TypeDeclaration(
+              baseName: 'Input',
+              associatedClass: emptyClass,
+              isNullable: true,
+            ),
             name: 'nested')
       ])
     ], enums: <Enum>[]);
@@ -664,16 +714,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Nested', isNullable: false))
+            returnType: TypeDeclaration(
+              baseName: 'Nested',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <NamedType>[
@@ -683,7 +737,11 @@ void main() {
       ]),
       Class(name: 'Nested', fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(baseName: 'Input', isNullable: true),
+            type: TypeDeclaration(
+              baseName: 'Input',
+              associatedClass: emptyClass,
+              isNullable: true,
+            ),
             name: 'nested')
       ])
     ], enums: <Enum>[]);
@@ -711,16 +769,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <NamedType>[
@@ -762,16 +824,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <NamedType>[
@@ -809,10 +875,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
@@ -849,10 +916,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
@@ -891,10 +959,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
@@ -931,10 +1000,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
@@ -972,9 +1042,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            parameters: <Parameter>[],
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <NamedType>[
@@ -1006,9 +1079,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            parameters: <Parameter>[],
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <NamedType>[
@@ -1040,9 +1116,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            parameters: <Parameter>[],
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <NamedType>[
@@ -1077,9 +1156,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false))
+            parameters: <Parameter>[],
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ))
       ])
     ], classes: <Class>[
       Class(name: 'Output', fields: <NamedType>[
@@ -1203,8 +1285,8 @@ void main() {
         Method(
             name: 'doit',
             returnType: const TypeDeclaration.voidDeclaration(),
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'foo',
                   type: const TypeDeclaration(
                       baseName: 'Map',
@@ -1238,10 +1320,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: 'input')
@@ -1287,16 +1370,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: 'input')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false),
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -1337,9 +1424,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false),
+            parameters: <Parameter>[],
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -1375,7 +1465,7 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
+            parameters: <Parameter>[],
             returnType: const TypeDeclaration.voidDeclaration(),
             isAsynchronous: true)
       ])
@@ -1406,16 +1496,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: '')
             ],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false),
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -1456,10 +1550,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[
-              NamedType(
-                  type: const TypeDeclaration(
+            parameters: <Parameter>[
+              Parameter(
+                  type: TypeDeclaration(
                     baseName: 'Input',
+                    associatedClass: emptyClass,
                     isNullable: false,
                   ),
                   name: 'foo')
@@ -1505,7 +1600,7 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
+            parameters: <Parameter>[],
             returnType: const TypeDeclaration.voidDeclaration(),
             isAsynchronous: true)
       ])
@@ -1536,9 +1631,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
             name: 'doSomething',
-            arguments: <NamedType>[],
-            returnType:
-                const TypeDeclaration(baseName: 'Output', isNullable: false),
+            parameters: <Parameter>[],
+            returnType: TypeDeclaration(
+              baseName: 'Output',
+              associatedClass: emptyClass,
+              isNullable: false,
+            ),
             isAsynchronous: true)
       ])
     ], classes: <Class>[
@@ -1618,7 +1716,7 @@ void main() {
   });
 
   test('field generics', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -1633,7 +1731,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -1661,8 +1759,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -1724,8 +1822,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -1784,8 +1882,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -1837,7 +1935,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1894,7 +1992,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1945,12 +2043,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -2015,12 +2113,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -2085,12 +2183,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -2151,13 +2249,13 @@ void main() {
             Method(
                 name: 'divide',
                 objcSelector: 'divideValue:by:',
-                arguments: <NamedType>[
-                  NamedType(
+                parameters: <Parameter>[
+                  Parameter(
                     type: const TypeDeclaration(
                         baseName: 'int', isNullable: false),
                     name: 'x',
                   ),
-                  NamedType(
+                  Parameter(
                     type: const TypeDeclaration(
                         baseName: 'int', isNullable: false),
                     name: 'y',
@@ -2287,7 +2385,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -2323,7 +2421,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -2356,7 +2454,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -2386,8 +2484,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -2443,8 +2541,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -2502,7 +2600,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[],
+              parameters: <Parameter>[],
               taskQueueType: TaskQueueType.serialBackgroundThread)
         ])
       ],
@@ -2555,8 +2653,8 @@ void main() {
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -2634,8 +2732,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -2672,16 +2770,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -2730,8 +2832,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
diff --git a/packages/pigeon/test/pigeon_lib_test.dart b/packages/pigeon/test/pigeon_lib_test.dart
index bf6e0ba33f5..dc0f6061e37 100644
--- a/packages/pigeon/test/pigeon_lib_test.dart
+++ b/packages/pigeon/test/pigeon_lib_test.dart
@@ -174,18 +174,18 @@ abstract class Api1 {
     expect(root.apis[0].name, equals('Api1'));
     expect(root.apis[0].methods.length, equals(1));
     expect(root.apis[0].methods[0].name, equals('doit'));
-    expect(root.apis[0].methods[0].arguments[0].name, equals('input'));
+    expect(root.apis[0].methods[0].parameters[0].name, equals('input'));
     expect(
-        root.apis[0].methods[0].arguments[0].type.baseName, equals('Input1'));
+        root.apis[0].methods[0].parameters[0].type.baseName, equals('Input1'));
     expect(root.apis[0].methods[0].returnType.baseName, equals('Output1'));
 
     Class? input;
     Class? output;
-    for (final Class klass in root.classes) {
-      if (klass.name == 'Input1') {
-        input = klass;
-      } else if (klass.name == 'Output1') {
-        output = klass;
+    for (final Class classDefinition in root.classes) {
+      if (classDefinition.name == 'Input1') {
+        input = classDefinition;
+      } else if (classDefinition.name == 'Output1') {
+        output = classDefinition;
       }
     }
     expect(input, isNotNull);
@@ -353,7 +353,7 @@ abstract class VoidArgApi {
     expect(results.root.apis[0].name, equals('VoidArgApi'));
     expect(
         results.root.apis[0].methods[0].returnType.baseName, equals('Output1'));
-    expect(results.root.apis[0].methods[0].arguments.isEmpty, isTrue);
+    expect(results.root.apis[0].methods[0].parameters.isEmpty, isTrue);
   });
 
   test('mockDartClass', () {
@@ -743,7 +743,7 @@ abstract class Api {
     final ParseResults parseResult = parseSource(code);
     expect(parseResult.errors.length, equals(1));
     expect(parseResult.errors[0].message,
-        contains('Generic type arguments must be nullable'));
+        contains('Generic type parameters must be nullable'));
     expect(parseResult.errors[0].message, contains('"list"'));
     expect(parseResult.errors[0].lineNumber, 2);
   });
@@ -864,14 +864,14 @@ abstract class Api {
 }
 ''';
     final ParseResults parseResult = parseSource(code);
+    expect(parseResult.root.apis[0].methods[0].parameters[1].type.baseName,
+        'List');
     expect(
-        parseResult.root.apis[0].methods[0].arguments[1].type.baseName, 'List');
-    expect(
-        parseResult.root.apis[0].methods[0].arguments[1].type.typeArguments[0]
+        parseResult.root.apis[0].methods[0].parameters[1].type.typeArguments[0]
             .baseName,
         'double');
     expect(
-        parseResult.root.apis[0].methods[0].arguments[1].type.typeArguments[0]
+        parseResult.root.apis[0].methods[0].parameters[1].type.typeArguments[0]
             .isNullable,
         isTrue);
   });
@@ -894,7 +894,7 @@ abstract class Api {
     expect(field.type.typeArguments[1].baseName, 'int');
   });
 
-  test('two arguments', () {
+  test('two parameters', () {
     const String code = '''
 class Input {
   String? input;
@@ -909,7 +909,7 @@ abstract class Api {
     expect(results.root.apis.length, 1);
     expect(results.root.apis[0].methods.length, equals(1));
     expect(results.root.apis[0].methods[0].name, equals('method'));
-    expect(results.root.apis[0].methods[0].arguments.length, 2);
+    expect(results.root.apis[0].methods[0].parameters.length, 2);
   });
 
   test('no type name argument', () {
@@ -923,7 +923,7 @@ abstract class Api {
     expect(results.errors.length, 1);
     expect(results.errors[0].lineNumber, 3);
     expect(results.errors[0].message,
-        contains('Arguments must specify their type'));
+        contains('Parameters must specify their type'));
   });
 
   test('custom objc selector', () {
@@ -954,10 +954,10 @@ abstract class Api {
     expect(results.errors.length, 1);
     expect(results.errors[0].lineNumber, 3);
     expect(results.errors[0].message,
-        contains('Invalid selector, expected 2 arguments'));
+        contains('Invalid selector, expected 2 parameters'));
   });
 
-  test('custom objc no arguments', () {
+  test('custom objc no parameters', () {
     const String code = '''
 @HostApi()
 abstract class Api {
@@ -1000,10 +1000,10 @@ abstract class Api {
     expect(results.errors.length, 1);
     expect(results.errors[0].lineNumber, 3);
     expect(results.errors[0].message,
-        contains('Invalid function signature, expected 2 arguments'));
+        contains('Invalid function signature, expected 2 parameters'));
   });
 
-  test('custom swift function signature no arguments', () {
+  test('custom swift function signature no parameters', () {
     const String code = '''
 @HostApi()
 abstract class Api {
@@ -1066,7 +1066,7 @@ abstract class Api {
     expect(results.root.classes[0].name, 'Foo');
   });
 
-  test('recurse into type arguments', () {
+  test('recurse into type parameters', () {
     const String code = '''
 class Foo {
   int? foo;
@@ -1234,7 +1234,7 @@ abstract class Api {
     final ParseResults results = parseSource(code);
     expect(results.errors.length, 0);
     expect(
-        results.root.apis[0].methods[0].arguments[0].type.isNullable, isTrue);
+        results.root.apis[0].methods[0].parameters[0].type.isNullable, isTrue);
   });
 
   test('task queue specified', () {
diff --git a/packages/pigeon/test/swift_generator_test.dart b/packages/pigeon/test/swift_generator_test.dart
index 622b51b6ec3..4c07b784eb7 100644
--- a/packages/pigeon/test/swift_generator_test.dart
+++ b/packages/pigeon/test/swift_generator_test.dart
@@ -8,9 +8,21 @@ import 'package:test/test.dart';
 
 import 'dart_generator_test.dart';
 
+final Class emptyClass = Class(name: 'className', fields: <NamedType>[
+  NamedType(
+    name: 'namedTypeName',
+    type: const TypeDeclaration(baseName: 'baseName', isNullable: false),
+  )
+]);
+
+final Enum emptyEnum = Enum(
+  name: 'enumName',
+  members: <EnumMember>[EnumMember(name: 'enumMemberName')],
+);
+
 void main() {
   test('gen one class', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -23,7 +35,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -76,11 +88,14 @@ void main() {
         Method(
             name: 'bar',
             returnType: const TypeDeclaration.voidDeclaration(),
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                   name: 'foo',
-                  type:
-                      const TypeDeclaration(baseName: 'Foo', isNullable: false))
+                  type: TypeDeclaration(
+                    baseName: 'Foo',
+                    associatedEnum: emptyEnum,
+                    isNullable: false,
+                  ))
             ])
       ])
     ], classes: <Class>[], enums: <Enum>[
@@ -108,16 +123,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -232,16 +251,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -282,10 +305,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
@@ -322,10 +346,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
@@ -363,9 +388,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -398,9 +426,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          parameters: <Parameter>[],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
         )
       ])
     ], classes: <Class>[
@@ -481,12 +512,13 @@ void main() {
   });
 
   test('gen nested', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Outer',
       fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Nested',
+              associatedClass: emptyClass,
               isNullable: true,
             ),
             name: 'nested')
@@ -505,7 +537,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass, nestedClass],
+      classes: <Class>[classDefinition, nestedClass],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -531,16 +563,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: 'arg')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -582,16 +618,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -635,12 +675,13 @@ void main() {
         EnumMember(name: 'two'),
       ],
     );
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'EnumClass',
       fields: <NamedType>[
         NamedType(
-            type: const TypeDeclaration(
+            type: TypeDeclaration(
               baseName: 'Enum1',
+              associatedEnum: emptyEnum,
               isNullable: true,
             ),
             name: 'enum1'),
@@ -648,7 +689,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[anEnum],
     );
     final StringBuffer sink = StringBuffer();
@@ -688,7 +729,7 @@ void main() {
   });
 
   test('generics - list', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -703,7 +744,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -721,7 +762,7 @@ void main() {
   });
 
   test('generics - maps', () {
-    final Class klass = Class(
+    final Class classDefinition = Class(
       name: 'Foobar',
       fields: <NamedType>[
         NamedType(
@@ -737,7 +778,7 @@ void main() {
     );
     final Root root = Root(
       apis: <Api>[],
-      classes: <Class>[klass],
+      classes: <Class>[classDefinition],
       enums: <Enum>[],
     );
     final StringBuffer sink = StringBuffer();
@@ -761,8 +802,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -796,8 +837,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     type: const TypeDeclaration(
                         baseName: 'List',
                         isNullable: false,
@@ -836,7 +877,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -869,7 +910,7 @@ void main() {
                   typeArguments: <TypeDeclaration>[
                     TypeDeclaration(baseName: 'int', isNullable: true)
                   ]),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -898,12 +939,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(isNullable: false, baseName: 'int')),
@@ -941,12 +982,12 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'add',
-          arguments: <NamedType>[
-            NamedType(
+          parameters: <Parameter>[
+            Parameter(
                 name: 'x',
                 type:
                     const TypeDeclaration(baseName: 'int', isNullable: false)),
-            NamedType(
+            Parameter(
                 name: 'y',
                 type:
                     const TypeDeclaration(baseName: 'int', isNullable: false)),
@@ -989,7 +1030,7 @@ void main() {
                 baseName: 'int',
                 isNullable: true,
               ),
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1019,7 +1060,7 @@ void main() {
                 isNullable: true,
               ),
               isAsynchronous: true,
-              arguments: <NamedType>[])
+              parameters: <Parameter>[])
         ])
       ],
       classes: <Class>[],
@@ -1048,8 +1089,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1084,8 +1125,8 @@ void main() {
           Method(
               name: 'doit',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                     name: 'foo',
                     type: const TypeDeclaration(
                       baseName: 'int',
@@ -1118,10 +1159,11 @@ void main() {
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
@@ -1177,8 +1219,8 @@ void main() {
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1252,8 +1294,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',
@@ -1286,16 +1328,20 @@ void main() {
       Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
         Method(
           name: 'doSomething',
-          arguments: <NamedType>[
-            NamedType(
-                type: const TypeDeclaration(
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
                   baseName: 'Input',
+                  associatedClass: emptyClass,
                   isNullable: false,
                 ),
                 name: '')
           ],
-          returnType:
-              const TypeDeclaration(baseName: 'Output', isNullable: false),
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            associatedClass: emptyClass,
+            isNullable: false,
+          ),
           isAsynchronous: true,
         )
       ])
@@ -1336,15 +1382,15 @@ void main() {
         Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
           Method(
             name: 'set',
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                 type: const TypeDeclaration(
                   baseName: 'int',
                   isNullable: false,
                 ),
                 name: 'value',
               ),
-              NamedType(
+              Parameter(
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: false,
@@ -1379,8 +1425,8 @@ void main() {
         Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
           Method(
             name: 'set',
-            arguments: <NamedType>[
-              NamedType(
+            parameters: <Parameter>[
+              Parameter(
                 type: const TypeDeclaration(
                   baseName: 'String',
                   isNullable: false,
@@ -1415,7 +1461,7 @@ void main() {
         Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
           Method(
             name: 'clear',
-            arguments: <NamedType>[],
+            parameters: <Parameter>[],
             swiftFunction: 'removeAll()',
             returnType: const TypeDeclaration.voidDeclaration(),
           )
@@ -1447,8 +1493,8 @@ void main() {
             Method(
               name: 'method',
               returnType: const TypeDeclaration.voidDeclaration(),
-              arguments: <NamedType>[
-                NamedType(
+              parameters: <Parameter>[
+                Parameter(
                   name: 'field',
                   type: const TypeDeclaration(
                     baseName: 'int',