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src/Compilers/CSharp/Portable/CSharpExtensions.cs

@@ -1214,6 +1214,15 @@ public static INamedTypeSymbol GetDeclaredSymbol(this SemanticModel semanticMode
             return csmodel?.GetDeclaredSymbol(declaratorSyntax, cancellationToken);
         }
 
+        /// <summary>
+        /// Given a syntax node of a tuple argument, get the tuple element symbol.
+        /// </summary>
+        public static ISymbol GetDeclaredSymbol(this SemanticModel semanticModel, ArgumentSyntax declaratorSyntax, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            var csmodel = semanticModel as CSharpSemanticModel;
+            return csmodel?.GetDeclaredSymbol(declaratorSyntax, cancellationToken);
+        }
+
         /// <summary>
         /// Given a syntax node that declares a property or member accessor, get the corresponding symbol.
         /// </summary>

src/Compilers/CSharp/Portable/Compilation/CSharpSemanticModel.cs

@@ -2694,7 +2694,7 @@ internal Conversion ClassifyConversionForCast(int position, ExpressionSyntax exp
         // 
         // This way IDEs can unambiguously implement such services as "Go to definition"
         //
-        // I.E. GetSymbolInfo for "tuple.Alice" should point to the same field as returned by GetDeclaredSymbol when applied to 
+        // I.E. GetSymbolInfo for "Bob" in "tuple.Bob" should point to the same field as returned by GetDeclaredSymbol when applied to 
         // the ArgumentSyntax "Bob: 2", since that is where the field was declared, where renames should be applied and so on.
         //                 
         //
@@ -2753,6 +2753,11 @@ internal Conversion ClassifyConversionForCast(int position, ExpressionSyntax exp
         /// <param name="declaratorSyntax">The argument syntax node.</param>
         /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>The symbol that was declared.</returns>
+        /// <remarks>
+        /// Generally ArgumentSyntax nodes do not declare symbols, except when used as aarguments of a tuple literal.
+        /// Example:  var x = (Alice: 1, Bob: 2);
+        ///           ArgumentSyntax "Alice: 1" declares a tuple element field "(int Alice, int Bob).Alice"
+        /// </remarks>
         public abstract ISymbol GetDeclaredSymbol(ArgumentSyntax declaratorSyntax, CancellationToken cancellationToken = default(CancellationToken));
 
         /// <summary>

src/Compilers/CSharp/Portable/GlobalSuppressions.cs

@@ -23,4 +23,5 @@
 [assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0027:Public API with optional parameter(s) should have the most parameters amongst its public overloads.", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.SyntaxFactory.ParenthesizedVariableComponent(Microsoft.CodeAnalysis.SeparatedSyntaxList{Microsoft.CodeAnalysis.CSharp.Syntax.VariableComponentSyntax})~Microsoft.CodeAnalysis.CSharp.Syntax.ParenthesizedVariableComponentSyntax")]
 [assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0027:Public API with optional parameter(s) should have the most parameters amongst its public overloads.", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.SyntaxFactory.ParenthesizedVariableDesignation(Microsoft.CodeAnalysis.SeparatedSyntaxList{Microsoft.CodeAnalysis.CSharp.Syntax.VariableDesignationSyntax})~Microsoft.CodeAnalysis.CSharp.Syntax.ParenthesizedVariableDesignationSyntax")]
 [assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetDeclaredSymbol(Microsoft.CodeAnalysis.SemanticModel,Microsoft.CodeAnalysis.CSharp.Syntax.TupleExpressionSyntax,System.Threading.CancellationToken)~Microsoft.CodeAnalysis.INamedTypeSymbol")]
+[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "<Pending>", Scope = "member", Target = "~M:Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetDeclaredSymbol(Microsoft.CodeAnalysis.SemanticModel,Microsoft.CodeAnalysis.CSharp.Syntax.ArgumentSyntax,System.Threading.CancellationToken)~Microsoft.CodeAnalysis.ISymbol")]
 

src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt

@@ -254,6 +254,7 @@ override Microsoft.CodeAnalysis.CSharp.Syntax.TupleTypeSyntax.Accept(Microsoft.C
 override Microsoft.CodeAnalysis.CSharp.Syntax.TupleTypeSyntax.Accept<TResult>(Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor<TResult> visitor) -> TResult
 override Microsoft.CodeAnalysis.CSharp.Syntax.WhenClauseSyntax.Accept(Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor visitor) -> void
 override Microsoft.CodeAnalysis.CSharp.Syntax.WhenClauseSyntax.Accept<TResult>(Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor<TResult> visitor) -> TResult
+static Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetDeclaredSymbol(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.CSharp.Syntax.ArgumentSyntax declaratorSyntax, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.ISymbol
 static Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetDeclaredSymbol(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.CSharp.Syntax.SingleVariableDesignationSyntax designationSyntax, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.ISymbol
 static Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetDeclaredSymbol(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.CSharp.Syntax.TupleElementSyntax declarationSyntax, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.ISymbol
 static Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetDeclaredSymbol(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.CSharp.Syntax.TupleExpressionSyntax declaratorSyntax, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.INamedTypeSymbol

src/Compilers/CSharp/Portable/Syntax/SyntaxFacts.cs

@@ -248,29 +248,43 @@ public static bool IsNamedArgumentName(SyntaxNode node)
             // Invocation, ObjectCreation, ObjectInitializer, or ElementAccess.
 
             if (!node.IsKind(IdentifierName))
+            { 
                 return false;
+            }
 
             var parent1 = node.Parent;
             if (parent1 == null || !parent1.IsKind(NameColon))
+            {
                 return false;
+            }
 
             var parent2 = parent1.Parent;
             if (parent2 == null || !(parent2.IsKind(Argument) || parent2.IsKind(AttributeArgument)))
+            {
                 return false;
+            }
 
             var parent3 = parent2.Parent;
-            if (parent3 == null) 
+            if (parent3 == null)
+            {
                 return false;
+            }
 
             if (parent3.IsKind(SyntaxKind.TupleExpression))
+            {
                 return true;
+            }
 
             if (!(parent3 is BaseArgumentListSyntax || parent3.IsKind(AttributeArgumentList)))
+            {
                 return false;
+            }
 
             var parent4 = parent3.Parent;
             if (parent4 == null)
+            {
                 return false;
+            }
 
             switch (parent4.Kind())
             {