Enforce new grammar rules that scoped keyword must be immediately followed by a type possibly “prefixed” by ref/ref readonly/in/out.

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -2500,9 +2500,6 @@ A catch() block after a catch (System.Exception e) block can catch non-CLS excep
   <data name="ERR_BadParameterModifiers" xml:space="preserve">
     <value> The parameter modifier '{0}' cannot be used with '{1}'</value>
   </data>
-  <data name="ERR_BadParameterModifiersOrder" xml:space="preserve">
-    <value> The parameter modifier '{0}' cannot follow '{1}'</value>
-  </data>
   <data name="ERR_BadTypeforThis" xml:space="preserve">
     <value>The first parameter of an extension method cannot be of type '{0}'</value>
   </data>
@@ -7235,7 +7232,4 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_ReadOnlyNotSuppAsParamModDidYouMeanIn" xml:space="preserve">
     <value>'readonly' is not supported as a parameter modifier. Did you mean 'in'?</value>
   </data>
-  <data name="ERR_ScopedNotBeforeType" xml:space="preserve">
-    <value>Invalid use of contextual keyword 'scoped'. The keyword should immediately precede the type or 'ref' keyword.</value>
-  </data>
 </root>

src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

@@ -1523,7 +1523,7 @@ internal enum ErrorCode
         ERR_TypeReserved = 8336,
         ERR_RefExtensionMustBeValueTypeOrConstrainedToOne = 8337,
         ERR_InExtensionMustBeValueType = 8338,
-        ERR_BadParameterModifiersOrder = 8339,
+        // ERR_BadParameterModifiersOrder = 8339,
 
         ERR_FieldsInRoStruct = 8340,
         ERR_AutoPropsInRoStruct = 8341,
@@ -2120,7 +2120,7 @@ internal enum ErrorCode
         ERR_FilePathCannotBeConvertedToUtf8 = 9069,
         ERR_ReadOnlyNotSuppAsParamModDidYouMeanIn = 9070,
         ERR_FileLocalDuplicateNameInNS = 9071,
-        ERR_ScopedNotBeforeType = 9072,
+        // Available 9072,
         WRN_ScopedMismatchInParameterOfTarget = 9073,
         WRN_ScopedMismatchInParameterOfOverrideOrImplementation = 9074,
 

src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs

@@ -2211,7 +2211,6 @@ internal static bool IsBuildOnlyDiagnostic(ErrorCode code)
                 case ErrorCode.ERR_FileTypeNameDisallowed:
                 case ErrorCode.ERR_FeatureNotAvailableInVersion11:
                 case ErrorCode.ERR_RefFieldInNonRefStruct:
-                case ErrorCode.ERR_BadParameterModifiersOrder:
                 case ErrorCode.WRN_AnalyzerReferencesNewerCompiler:
                 case ErrorCode.ERR_CannotMatchOnINumberBase:
                 case ErrorCode.ERR_ScopedTypeNameDisallowed:
@@ -2223,7 +2222,6 @@ internal static bool IsBuildOnlyDiagnostic(ErrorCode code)
                 case ErrorCode.ERR_FilePathCannotBeConvertedToUtf8:
                 case ErrorCode.ERR_ReadOnlyNotSuppAsParamModDidYouMeanIn:
                 case ErrorCode.ERR_FileLocalDuplicateNameInNS:
-                case ErrorCode.ERR_ScopedNotBeforeType:
                 case ErrorCode.WRN_ScopedMismatchInParameterOfTarget:
                 case ErrorCode.WRN_ScopedMismatchInParameterOfOverrideOrImplementation:
                     return false;

src/Compilers/CSharp/Portable/Symbols/Source/ParameterHelpers.cs

@@ -428,7 +428,7 @@ internal static void CheckParameterModifiers(
             var seenOut = false;
             var seenParams = false;
             var seenIn = false;
-            bool scopedBeforeRef = false;
+            bool seenScoped = false;
 
             foreach (var modifier in parameter.Modifiers)
             {
@@ -582,29 +582,12 @@ internal static void CheckParameterModifiers(
 
                     case SyntaxKind.ScopedKeyword when !parsingFunctionPointerParams:
                         ModifierUtils.CheckScopedModifierAvailability(parameter, modifier, diagnostics);
-                        if (seenIn)
-                        {
-                            addERR_BadParameterModifiersOrder(diagnostics, modifier, SyntaxKind.InKeyword);
-                        }
-                        else if (seenOut)
-                        {
-                            addERR_BadParameterModifiersOrder(diagnostics, modifier, SyntaxKind.OutKeyword);
-                        }
-                        else if (seenRef)
-                        {
-                            addERR_BadParameterModifiersOrder(diagnostics, modifier, SyntaxKind.RefKeyword);
-                        }
-                        else
-                        {
-                            if (scopedBeforeRef)
-                            {
-                                addERR_DupParamMod(diagnostics, modifier);
-                            }
-                            else
-                            {
-                                scopedBeforeRef = true;
-                            }
-                        }
+                        Debug.Assert(!seenIn);
+                        Debug.Assert(!seenOut);
+                        Debug.Assert(!seenRef);
+                        Debug.Assert(!seenScoped);
+
+                        seenScoped = true;
                         break;
 
                     case SyntaxKind.ReadOnlyKeyword:
@@ -626,11 +609,6 @@ static void addERR_DupParamMod(BindingDiagnosticBag diagnostics, SyntaxToken mod
                 diagnostics.Add(ErrorCode.ERR_DupParamMod, modifier.GetLocation(), SyntaxFacts.GetText(modifier.Kind()));
             }
 
-            static void addERR_BadParameterModifiersOrder(BindingDiagnosticBag diagnostics, SyntaxToken modifier, SyntaxKind otherModifierKind)
-            {
-                diagnostics.Add(ErrorCode.ERR_BadParameterModifiersOrder, modifier.GetLocation(), SyntaxFacts.GetText(modifier.Kind()), SyntaxFacts.GetText(otherModifierKind));
-            }
-
             static void addERR_BadParameterModifiers(BindingDiagnosticBag diagnostics, SyntaxToken modifier, SyntaxKind otherModifierKind)
             {
                 diagnostics.Add(ErrorCode.ERR_BadParameterModifiers, modifier.GetLocation(), SyntaxFacts.GetText(modifier.Kind()), SyntaxFacts.GetText(otherModifierKind));
@@ -917,7 +895,7 @@ internal static MethodSymbol FindContainingGenericMethod(Symbol symbol)
         internal static RefKind GetModifiers(SyntaxTokenList modifiers, out SyntaxToken refnessKeyword, out SyntaxToken paramsKeyword, out SyntaxToken thisKeyword, out DeclarationScope scope)
         {
             var refKind = RefKind.None;
-            bool scopedBeforeRef = false;
+            bool isScoped = false;
 
             refnessKeyword = default(SyntaxToken);
             paramsKeyword = default(SyntaxToken);
@@ -955,15 +933,13 @@ internal static RefKind GetModifiers(SyntaxTokenList modifiers, out SyntaxToken
                         thisKeyword = modifier;
                         break;
                     case SyntaxKind.ScopedKeyword:
-                        if (refKind == RefKind.None)
-                        {
-                            scopedBeforeRef = true;
-                        }
+                        Debug.Assert(refKind == RefKind.None);
+                        isScoped = true;
                         break;
                 }
             }
 
-            if (scopedBeforeRef)
+            if (isScoped)
             {
                 scope = (refKind == RefKind.None) ? DeclarationScope.ValueScoped : DeclarationScope.RefScoped;
             }