Add tests

src/EditorFeatures/CSharpTest/MakeLocalFunctionStatic/MakeLocalFunctionStaticTests.cs

@@ -4,11 +4,9 @@
 using Microsoft.CodeAnalysis.CodeFixes;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.MakeLocalFunctionStatic;
-using Microsoft.CodeAnalysis.CSharp.UseLocalFunction;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.Diagnostics;
 using Microsoft.CodeAnalysis.Test.Utilities;
-using Roslyn.Test.Utilities;
 using Xunit;
 
 namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.MakeLocalFunctionStatic
@@ -124,5 +122,38 @@ void M()
     }
 }", parameters: new TestParameters(parseOptions: CSharp8ParseOptions));
         }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsMakeLocalFunctionStatic)]
+        public async Task TestAsyncFunction()
+        {
+            await TestInRegularAndScriptAsync(
+@"using System;
+using System.Threading.Tasks;
+
+class C
+{
+    void M()
+    {
+        async Task<int> [||]fibonacci(int n)
+        {
+            return n <= 1 ? n : await fibonacci(n - 1) + await fibonacci(n - 2);
+        }
+    }
+}",
+@"using System;
+using System.Threading.Tasks;
+
+class C
+{
+    void M()
+    {
+        static async Task<int> fibonacci(int n)
+        {
+            return n <= 1 ? n : await fibonacci(n - 1) + await fibonacci(n - 2);
+        }
+    }
+}",
+parseOptions: CSharp8ParseOptions);
+        }
     }
 }

src/Workspaces/CSharp/Portable/CodeGeneration/CSharpSyntaxGenerator.cs

@@ -1534,7 +1534,7 @@ public override SyntaxNode WithAccessibility(SyntaxNode declaration, Accessibili
         private static readonly DeclarationModifiers s_structModifiers = DeclarationModifiers.New | DeclarationModifiers.Partial | DeclarationModifiers.ReadOnly | DeclarationModifiers.Ref;
         private static readonly DeclarationModifiers s_interfaceModifiers = DeclarationModifiers.New | DeclarationModifiers.Partial;
         private static readonly DeclarationModifiers s_accessorModifiers = DeclarationModifiers.Abstract | DeclarationModifiers.New | DeclarationModifiers.Override | DeclarationModifiers.Virtual;
-        private static readonly DeclarationModifiers s_localFunctionModifiers = DeclarationModifiers.Static;
+        private static readonly DeclarationModifiers s_localFunctionModifiers = DeclarationModifiers.Async | DeclarationModifiers.Static;
 
         private static DeclarationModifiers GetAllowedModifiers(SyntaxKind kind)
         {