Issue 42093. Add async test.

[email protected]

Bug: #42093
Change-Id: I96b5c1597d7d16b269b6f6c7d3fd67bd960ff589
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/149604
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/test/src/diagnostics/return_of_invalid_type_test.dart

@@ -361,13 +361,17 @@ Future<void> f() async {
     ]);
   }
 
-  test_function_async_expression_dynamic__to_Future_int() async {
-    await assertNoErrorsInCode(r'''
-Future<int> f(dynamic a) async => a; 
-''');
+  test_function_async_block_void__to_Future_Null() async {
+    await assertErrorsInCode(r'''
+Future<Null> f(void a) async {
+  return a;
+}
+''', [
+      error(StaticTypeWarningCode.RETURN_OF_INVALID_TYPE_FROM_FUNCTION, 40, 1),
+    ]);
   }
 
-  test_function_async_void__to_FutureOr_ObjectQ() async {
+  test_function_async_block_void__to_FutureOr_ObjectQ() async {
     await assertErrorsInCode(r'''
 import 'dart:async';
 
@@ -379,6 +383,12 @@ FutureOr<Object?> f(void a) async {
     ]);
   }
 
+  test_function_async_expression_dynamic__to_Future_int() async {
+    await assertNoErrorsInCode(r'''
+Future<int> f(dynamic a) async => a; 
+''');
+  }
+
   test_functionExpression_async_futureOr_void__to_Object() async {
     await assertNoErrorsInCode(r'''
 void a = null;