Better handle parameter names.

src/Features/Core/Portable/InitializeParameter/AbstractInitializeParameterCodeRefactoringProvider.cs

@@ -59,7 +59,7 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
             if (!context.Span.IsEmpty)
             {
                 var parameterName = syntaxFacts.GetNameOfParameter(parameterNode);
-                if (parameterName.Span != context.Span)
+                if (parameterName == null || parameterName.Value.Span != context.Span)
                 {
                     return;
                 }

src/Workspaces/CSharp/Portable/LanguageServices/CSharpSyntaxFactsService.cs

@@ -204,8 +204,8 @@ public bool IsGenericName(SyntaxNode node)
         public bool IsNamedParameter(SyntaxNode node)
             => node.CheckParent<NameColonSyntax>(p => p.Name == node);
 
-        public SyntaxToken GetNameOfParameter(SyntaxNode node)
-            => (node as ParameterSyntax)?.Identifier ?? default;
+        public SyntaxToken? GetNameOfParameter(SyntaxNode node)
+            => (node as ParameterSyntax)?.Identifier;
 
         public SyntaxNode GetDefaultOfParameter(SyntaxNode node)
             => (node as ParameterSyntax)?.Default;

src/Workspaces/Core/Portable/LanguageServices/SyntaxFactsService/ISyntaxFactsService.cs

@@ -154,7 +154,7 @@ internal interface ISyntaxFactsService : ILanguageService
         bool IsPointerMemberAccessExpression(SyntaxNode node);
 
         bool IsNamedParameter(SyntaxNode node);
-        SyntaxToken GetNameOfParameter(SyntaxNode node);
+        SyntaxToken? GetNameOfParameter(SyntaxNode node);
         SyntaxNode GetDefaultOfParameter(SyntaxNode node);
         SyntaxNode GetParameterList(SyntaxNode node);
 

src/Workspaces/VisualBasic/Portable/LanguageServices/VisualBasicSyntaxFactsService.vb

@@ -206,8 +206,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             Return node.CheckParent(Of SimpleArgumentSyntax)(Function(p) p.IsNamed AndAlso p.NameColonEquals.Name Is node)
         End Function
 
-        Public Function GetNameOfParameter(node As SyntaxNode) As SyntaxToken Implements ISyntaxFactsService.GetNameOfParameter
-            Return If(TryCast(node, ParameterSyntax)?.Identifier?.Identifier, New SyntaxToken())
+        Public Function GetNameOfParameter(node As SyntaxNode) As SyntaxToken? Implements ISyntaxFactsService.GetNameOfParameter
+            Return TryCast(node, ParameterSyntax)?.Identifier?.Identifier
         End Function
 
         Public Function GetDefaultOfParameter(node As SyntaxNode) As SyntaxNode Implements ISyntaxFactsService.GetDefaultOfParameter