Merge pull request #16351 from CyrusNajmabadi/parserDiagnostics32

Move errors about params/__arglist being last out of the parser.

src/Compilers/CSharp/Portable/Parser/LanguageParser.cs

@@ -3816,11 +3816,6 @@ private static bool CanReuseBracketedParameterList(CSharp.Syntax.BracketedParame
                 if (this.CurrentToken.Kind != closeKind)
                 {
 tryAgain:
-                    int mustBeLastIndex = -1;
-                    bool mustBeLastHadParams = false;
-                    bool hasParams = false;
-                    bool hasArgList = false;
-
                     if (this.IsPossibleParameter() || this.CurrentToken.Kind == SyntaxKind.CommaToken)
                     {
                         // first parameter
@@ -3828,14 +3823,6 @@ private static bool CanReuseBracketedParameterList(CSharp.Syntax.BracketedParame
                         modifiers.Clear();
                         var parameter = this.ParseParameter(attributes, modifiers);
                         nodes.Add(parameter);
-                        hasParams = modifiers.Any((int)SyntaxKind.ParamsKeyword);
-                        hasArgList = parameter.Identifier.Kind == SyntaxKind.ArgListKeyword;
-                        bool mustBeLast = hasParams || hasArgList;
-                        if (mustBeLast && mustBeLastIndex == -1)
-                        {
-                            mustBeLastIndex = nodes.Count - 1;
-                            mustBeLastHadParams = hasParams;
-                        }
 
                         // additional parameters
                         while (true)
@@ -3857,15 +3844,6 @@ private static bool CanReuseBracketedParameterList(CSharp.Syntax.BracketedParame
                                 }
 
                                 nodes.Add(parameter);
-                                hasParams = modifiers.Any((int)SyntaxKind.ParamsKeyword);
-                                hasArgList = parameter.Identifier.Kind == SyntaxKind.ArgListKeyword;
-                                mustBeLast = hasParams || hasArgList;
-                                if (mustBeLast && mustBeLastIndex == -1)
-                                {
-                                    mustBeLastIndex = nodes.Count - 1;
-                                    mustBeLastHadParams = hasParams;
-                                }
-
                                 continue;
                             }
                             else if (this.SkipBadParameterListTokens(ref open, nodes, SyntaxKind.CommaToken, closeKind) == PostSkipAction.Abort)
@@ -3878,11 +3856,6 @@ private static bool CanReuseBracketedParameterList(CSharp.Syntax.BracketedParame
                     {
                         goto tryAgain;
                     }
-
-                    if (mustBeLastIndex >= 0 && mustBeLastIndex < nodes.Count - 1)
-                    {
-                        nodes[mustBeLastIndex] = this.AddError(nodes[mustBeLastIndex], mustBeLastHadParams ? ErrorCode.ERR_ParamsLast : ErrorCode.ERR_VarargsLast);
-                    }
                 }
 
                 _termState = saveTerm;

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

@@ -28,10 +28,19 @@ internal static class ParameterHelpers
             int firstDefault = -1;
 
             var builder = ArrayBuilder<ParameterSymbol>.GetInstance();
-            ImmutableArray<ParameterSymbol> parameters;
+            var mustBeLastParameter = (ParameterSyntax)null;
 
             foreach (var parameterSyntax in syntax.Parameters)
             {
+                if (mustBeLastParameter == null)
+                {
+                    if (parameterSyntax.Modifiers.Any(SyntaxKind.ParamsKeyword) ||
+                        parameterSyntax.Identifier.Kind() == SyntaxKind.ArgListKeyword)
+                    {
+                        mustBeLastParameter = parameterSyntax;
+                    }
+                }
+
                 CheckParameterModifiers(parameterSyntax, diagnostics);
 
                 var refKind = GetModifiers(parameterSyntax.Modifiers,
@@ -92,7 +101,16 @@ internal static class ParameterHelpers
                 ++parameterIndex;
             }
 
-            parameters = builder.ToImmutableAndFree();
+            if (mustBeLastParameter != null && mustBeLastParameter != syntax.Parameters.Last())
+            {
+                diagnostics.Add(
+                    mustBeLastParameter.Identifier.Kind() == SyntaxKind.ArgListKeyword
+                        ? ErrorCode.ERR_VarargsLast
+                        : ErrorCode.ERR_ParamsLast,
+                    mustBeLastParameter.GetLocation());
+            }
+
+            ImmutableArray<ParameterSymbol> parameters = builder.ToImmutableAndFree();
 
             var methodOwner = owner as MethodSymbol;
             var typeParameters = (object)methodOwner != null ?

src/Compilers/CSharp/Test/Syntax/Parsing/DeclarationParsingTests.cs

@@ -5397,8 +5397,14 @@ class C
    void M(__arglist, int j)  {}
 }";
 
-            TestError(text1, ErrorCode.ERR_ParamsLast);
-            TestError(text2, ErrorCode.ERR_VarargsLast);
+            CreateCompilationWithMscorlib(text1).VerifyDiagnostics(
+                // (4,11): error CS0231: A params parameter must be the last parameter in a formal parameter list
+                //    void M(params int[] i, int j)  {}
+                Diagnostic(ErrorCode.ERR_ParamsLast, "params int[] i").WithLocation(4, 11));
+            CreateCompilationWithMscorlib(text2).VerifyDiagnostics(
+                // (4,11): error CS0257: An __arglist parameter must be the last parameter in a formal parameter list
+                //    void M(__arglist, int j)  {}
+                Diagnostic(ErrorCode.ERR_VarargsLast, "__arglist").WithLocation(4, 11));
         }
 
         [Fact]

src/Compilers/CSharp/Test/Syntax/Parsing/ParserErrorMessageTests.cs

@@ -317,7 +317,6 @@ public struct st { }
         public void CS0231ERR_ParamsLast()
         {
             var test = @"
-using System;
 public class MyClass {
     public void MyMeth(params int[] values, int i) {}
     public static int Main() {
@@ -326,7 +325,10 @@ public class MyClass {
 }
 ";
 
-            ParseAndValidate(test, Diagnostic(ErrorCode.ERR_ParamsLast, "params int[] values"));
+            CreateCompilationWithMscorlib45(test).VerifyDiagnostics(
+                // (3,24): error CS0231: A params parameter must be the last parameter in a formal parameter list
+                //     public void MyMeth(params int[] values, int i) {}
+                Diagnostic(ErrorCode.ERR_ParamsLast, "params int[] values").WithLocation(3, 24));
         }
 
         [Fact]
@@ -341,10 +343,10 @@ public void Bar(__arglist,  int b)
 }
 ";
 
-            ParseAndValidate(test,
-    // (4,19): error CS0257: An __arglist parameter must be the last parameter in a formal parameter list
-    //   public void Bar(__arglist,  int b)
-    Diagnostic(ErrorCode.ERR_VarargsLast, "__arglist"));
+            CreateCompilationWithMscorlib(test).VerifyDiagnostics(
+                // (4,19): error CS0257: An __arglist parameter must be the last parameter in a formal parameter list
+                //   public void Bar(__arglist,  int b)
+                Diagnostic(ErrorCode.ERR_VarargsLast, "__arglist"));
         }
 
         [WorkItem(536668, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/536668")]