Fix InvalidCastException thrown from VSTHRD102

src/Microsoft.VisualStudio.Threading.Analyzers.CSharp/CSharpCommonInterest.cs

@@ -176,9 +176,8 @@ private static bool IsTaskCompletedWithWhenAll(SyntaxNodeAnalysisContext context
             MemberAccessExpressionSyntax? memberAccess = memberAccessList.First();
 
             // Does the invocation have the expected `Task.WhenAll` syntax? This is cheaper to verify before looking up its semantic type.
-            var correctSyntax =
-                ((IdentifierNameSyntax)memberAccess.Expression).Identifier.ValueText == Types.Task.TypeName &&
-                ((IdentifierNameSyntax)memberAccess.Name).Identifier.ValueText == Types.Task.WhenAll;
+            bool correctSyntax = memberAccess.Expression is IdentifierNameSyntax { Identifier.ValueText: Types.Task.TypeName }
+                && memberAccess.Name is IdentifierNameSyntax { Identifier.ValueText: Types.Task.WhenAll };
 
             if (!correctSyntax)
             {

test/Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD102AvoidJtfRunInNonPublicMembersAnalyzerTests.cs

@@ -353,6 +353,36 @@ public class Test {
 
     public void Advise(Action<int> foo) { }
 }
+";
+            await Verify.VerifyAnalyzerAsync(test);
+        }
+
+        [Fact]
+        public async Task JtfRunInPrivateMethod__WithMultiMemberAccessExpression_ProducesDiagnostic()
+        {
+            var test = @"
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.Threading;
+
+class Other {
+    internal static JoinableTaskFactory factory;
+}
+
+class Test {
+    Foo foo;
+    JoinableTaskFactory jtf;
+
+    void F() {
+        object v = Other.factory.[|Run|](async () => { return await this.foo.DoSomethingAsync(); });
+        jtf.[|Run|](async delegate {
+            await jtf.SwitchToMainThreadAsync();
+        });
+    }
+
+    class Foo {
+        internal Task<object> DoSomethingAsync() => new TaskCompletionSource<object>().Task;
+    }
+}
 ";
             await Verify.VerifyAnalyzerAsync(test);
         }