Report ERR_MethodArgCantBeRefAny for “out var” declarations without...

Report ERR_MethodArgCantBeRefAny for “out var” declarations without initializers. This is a port of https://roslyn.codeplex.com/SourceControl/changeset/4b562c0061233f3e3a76de510ecd68b2d37fa1b1. (changeset 1250556)

Src/Compilers/CSharp/Source/Binder/Binder_Expressions.cs

@@ -2946,10 +2946,26 @@ private void BindArgumentsAndNames(BracketedArgumentListSyntax argumentListOpt,
                 }
                 else if (argument.Kind == BoundKind.UninitializedVarDeclarationExpression)
                 {
-                    arguments[arg] = ((UninitializedVarDeclarationExpression)argument).SetInferredType(GetCorrespondingParameterType(ref result, parameters, arg), success: true);
+                    TypeSymbol parameterType = GetCorrespondingParameterType(ref result, parameters, arg);
+                    bool hasErrors = false;
+
+                    if (this.ContainingMemberOrLambda.Kind == SymbolKind.Method
+                        && ((MethodSymbol)this.ContainingMemberOrLambda).IsAsync
+                        && parameterType.IsRestrictedType())
+                    {
+                        Error(diagnostics, ErrorCode.ERR_BadSpecialByRefLocal,
+                              argument.Syntax.CSharpKind() == SyntaxKind.DeclarationExpression ?
+                                    ((DeclarationExpressionSyntax)argument.Syntax).Type :
+                                    argument.Syntax,
+                              parameterType);
+
+                        hasErrors = true;
+                    }
+
+                    arguments[arg] = ((UninitializedVarDeclarationExpression)argument).SetInferredType(parameterType, success: !hasErrors);
                 }
             }
-            }
+        }
 
         private static TypeSymbol GetCorrespondingParameterType(ref MemberAnalysisResult result, ImmutableArray<ParameterSymbol> parameters, int arg)
         {

Src/Compilers/CSharp/Test/Semantic/Semantics/DeclarationExpressionsTests.cs

@@ -3994,5 +3994,48 @@ public static void Main()
                 );
         }
 
+        [Fact]
+        public void RestrictedType()
+        {
+            var source = @"
+using System.Threading.Tasks;
+using System;
+
+class Test
+{
+    static void Main() {}
+
+    async Task M1()
+    {
+        M1(out TypedReference x);
+        M1(out var y);
+        await Task.Factory.StartNew(() => { });
+    }
+
+    void M1(out TypedReference tr)
+    {
+        tr = default(TypedReference);
+    }
+
+    Task M2()
+    {
+        M1(out TypedReference x);
+        M1(out var y);
+        return null;
+    }
+}";
+            CreateCompilationWithMscorlib45(source, parseOptions: TestOptions.Regular.WithLanguageVersion(LanguageVersion.Experimental)).VerifyDiagnostics(
+    // (16,13): error CS1601: Cannot make reference to variable of type 'System.TypedReference'
+    //     void M1(out TypedReference tr)
+    Diagnostic(ErrorCode.ERR_MethodArgCantBeRefAny, "out TypedReference tr").WithArguments("System.TypedReference").WithLocation(16, 13),
+    // (11,16): error CS4012: Parameters or locals of type 'System.TypedReference' cannot be declared in async methods or lambda expressions.
+    //         M1(out TypedReference x);
+    Diagnostic(ErrorCode.ERR_BadSpecialByRefLocal, "TypedReference").WithArguments("System.TypedReference").WithLocation(11, 16),
+    // (12,16): error CS4012: Parameters or locals of type 'System.TypedReference' cannot be declared in async methods or lambda expressions.
+    //         M1(out var y);
+    Diagnostic(ErrorCode.ERR_BadSpecialByRefLocal, "var").WithArguments("System.TypedReference").WithLocation(12, 16)
+                );
+        }
+
     }
 }
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