Fix async_test problems.

pkg/compiler/lib/src/resolution/members.dart

 // Copyright (c) 2012, 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.
 
 part of resolution;
 
 abstract class TreeElements {
   AnalyzableElement get analyzedElement;
   Iterable<Node> get superUses;
 
@@ skipping 498 matching lines @@
         element.asyncMarker = AsyncMarker.SYNC_STAR;
       }
       if (element.isAbstract) {
         compiler.reportError(asyncModifier,
             MessageKind.ASYNC_MODIFIER_ON_ABSTRACT_METHOD,
             {'modifier': element.asyncMarker});
       } else if (element.isConstructor) {
         compiler.reportError(asyncModifier,
             MessageKind.ASYNC_MODIFIER_ON_CONSTRUCTOR,
             {'modifier': element.asyncMarker});
-      } else if (functionExpression.body.asReturn() != null &&
+      } else {
+        if (element.isSetter) {
+          compiler.reportError(asyncModifier,
+              MessageKind.ASYNC_MODIFIER_ON_SETTER,
+              {'modifier': element.asyncMarker});
+
+        }
+        if (functionExpression.body.asReturn() != null &&
                  element.asyncMarker.isYielding) {
-        compiler.reportError(asyncModifier,
-            MessageKind.YIELDING_MODIFIER_ON_ARROW_BODY,
-            {'modifier': element.asyncMarker});
+          compiler.reportError(asyncModifier,
+              MessageKind.YIELDING_MODIFIER_ON_ARROW_BODY,
+              {'modifier': element.asyncMarker});
+        }
       }
     }
   }
 
   TreeElements resolveMethodElementImplementation(
       FunctionElement element, FunctionExpression tree) {
     return compiler.withCurrentElement(element, () {
       if (element.isExternal && tree.hasBody()) {
         compiler.reportError(element,
             MessageKind.EXTERNAL_WITH_BODY,
@@ skipping 4492 matching lines @@
 }
 
 /// The result for the resolution of the `assert` method.
 class AssertResult implements ResolutionResult {
   const AssertResult();
 
   Element get element => null;
 
   String toString() => 'AssertResult()';
 }