fix: multiple generations for same class

examples/envied_example/.gitignore

@@ -1,6 +1,7 @@
 # Files and directories created by pub.
 .dart_tool/
 .packages
+.pubspec.lock
 
 # Conventional directory for build output.
 build/

examples/envied_example/lib/envs.env.dart

@@ -0,0 +1,66 @@
+// lib/env.dart
+import 'package:envied/envied.dart';
+import 'package:example/example_enum.dart';
+
+import 'app_env_fields.dart';
+
+part 'envs.env.g.dart';
+
+@Envied(
+    path: '.env_debug',
+    name: 'Dev',
+    allowOptionalFields: true,
+    interpolate: false,
+    obfuscate: false,
+    requireEnvFile: true,
+    rawStrings: true,
+    useConstantCase: false,
+    randomSeed: 1)
+@Envied(path: '.env', name: 'Prod')
+final class Envs implements AppEnvFields {
+  /// NOTE: This is here just as an example!
+  ///
+  /// In a Flutter app you would normally import this like so
+  /// import 'package:flutter/foundation.dart';
+  static const kDebugMode = true;
+
+  factory Envs() => _instance;
+
+  static dynamic _instance = kDebugMode ? _Dev() : _Prod();
+
+  @override
+  @EnviedField(varName: 'KEY1')
+  final String key1 = _instance.key1;
+
+  @override
+  @EnviedField(varName: 'KEY2')
+  final String key2 = _instance.key2;
+
+  @override
+  @EnviedField()
+  final String key3 = _instance.key3;
+
+  @override
+  @EnviedField()
+  final int key4 = _instance.key4;
+
+  @override
+  @EnviedField()
+  final bool key5 = _instance.key5;
+
+  @override
+  @EnviedField()
+  final Uri key6 = _instance.key6;
+
+  @override
+  @EnviedField()
+  final DateTime key7 = _instance.key7;
+
+  @override
+  @EnviedField()
+  final ExampleEnum key8 = _instance.key8;
+
+  @override
+  @EnviedField(rawString: true)
+  final String key9 = _instance.key9;
+}