Colorize async as keyword in some cases

src/EditorFeatures/CSharpTest/Classification/TotalClassifierTests.cs

@@ -2290,6 +2290,96 @@ static void Main(string[] args)
 Parameter("args"),
 Punctuation.CloseParen,
 Punctuation.OpenCurly,
+Punctuation.CloseCurly);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        [WorkItem(60399, "https://github.com/dotnet/roslyn/issues/60339")]
+        public async Task TestAsyncInIncompleteMember(TestHost testHost)
+        {
+            await TestAsync(
+@"class Test
+{
+    public async
+}",
+                testHost,
+                parseOptions: null,
+Keyword("class"),
+Class("Test"),
+Punctuation.OpenCurly,
+Keyword("public"),
+Keyword("async"),
+Punctuation.CloseCurly);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        [WorkItem(60399, "https://github.com/dotnet/roslyn/issues/60339")]
+        public async Task TestAsyncInIncompleteMemberWhenAsyncTypeIsDefined(TestHost testHost)
+        {
+            await TestAsync(
+@"[|class Test
+{
+    public async
+}|]
+
+class async
+{
+}",
+                testHost,
+                parseOptions: null,
+Keyword("class"),
+Class("Test"),
+Punctuation.OpenCurly,
+Keyword("public"),
+Class("async"),
+Punctuation.CloseCurly);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        [WorkItem(60399, "https://github.com/dotnet/roslyn/issues/60339")]
+        public async Task TestAsyncInPotentialLocalFunctionDeclaration(TestHost testHost)
+        {
+            await TestAsync(
+@"void M()
+{
+    async
+}",
+                testHost,
+                parseOptions: null,
+Keyword("void"),
+Method("M"),
+Punctuation.OpenParen,
+Punctuation.CloseParen,
+Punctuation.OpenCurly,
+Keyword("async"),
+Punctuation.CloseCurly);
+        }
+
+        [Theory]
+        [CombinatorialData]
+        [WorkItem(60399, "https://github.com/dotnet/roslyn/issues/60339")]
+        public async Task TestAsyncInPotentialLocalFunctionDeclarationWhenAsyncTypeIsDefined(TestHost testHost)
+        {
+            await TestAsync(
+@"[|void M()
+{
+    async
+}|]
+
+class async
+{
+}",
+                testHost,
+                parseOptions: null,
+Keyword("void"),
+Method("M"),
+Punctuation.OpenParen,
+Punctuation.CloseParen,
+Punctuation.OpenCurly,
+Class("async"),
 Punctuation.CloseCurly);
         }
     }

src/Workspaces/CSharp/Portable/Classification/SyntaxClassification/NameSyntaxClassifier.cs

@@ -182,6 +182,31 @@ private static bool TryClassifySymbol(
                 return true;
             }
 
+            if (name is IdentifierNameSyntax { Identifier.Text: "async" } && symbol is null)
+            {
+                // MemberDeclarationSyntax examle:
+                //
+                // class Test
+                // {
+                //   public async
+                // }
+                //
+                // ExpressionStatementSyntax example:
+                //
+                // void M()
+                // {
+                //   async
+                // }
+                //
+                // User is probably defining an async local function here
+                if ((name.Parent is MemberDeclarationSyntax memberDeclaration && !memberDeclaration.Modifiers.Any(SyntaxKind.AsyncKeyword)) ||
+                    name.Parent is ExpressionStatementSyntax)
+                {
+                    classifiedSpan = new ClassifiedSpan(name.Span, ClassificationTypeNames.Keyword);
+                    return true;
+                }
+            }
+
             if (name.IsNint || name.IsNuint)
             {
                 if (symbol is ITypeSymbol type && type.IsNativeIntegerType)