Band-aid fix for issue #24191.

pkg/analyzer/test/generated/non_error_resolver_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library engine.non_error_resolver_test;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
@@ skipping 2970 matching lines @@
 }
 main() {
   Functor f = new Functor();
   f();
 }''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
+  void test_issue_24191() {
+    Source source = addSource('''
+import 'dart:async';
+
+class S extends Stream {}
+f(S s) async {
+  await for (var v in s) {
+    print(v);
+  }
+}
+''');
+    computeLibrarySourceErrors(source);
+    assertNoErrors(source);
+    verify([source]);
+  }
+
   void test_listElementTypeNotAssignable() {
     Source source = addSource(r'''
 var v1 = <int> [42];
 var v2 = const <int> [42];''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
   void test_loadLibraryDefined() {
@@ skipping 2699 matching lines @@
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "a");
   }
 
   CompilationUnit _getResolvedLibraryUnit(Source source) =>
       analysisContext.getResolvedCompilationUnit2(source, source);
 }