Remove AsyncError with Expando.

pkg/unittest/lib/src/core_matchers.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 matcher;
 
 /**
  * Returns a matcher that matches empty strings, maps or iterables
  * (including collections).
  */
@@ skipping 308 matching lines @@
 
   bool matches(item, MatchState matchState) {
     if (item is! Function && item is! Future) return false;
     if (item is Future) {
       var done = wrapAsync((fn) => fn());
 
       // Queue up an asynchronous expectation that validates when the future
       // completes.
       item.then((value) {
         done(() => fail("Expected future to fail, but succeeded with '$value'."));
-      }, onError: (e) {
+      }, onError: (error) {
         done(() {
           if (_matcher == null) return;
           var reason;
-          if (e.stackTrace != null) {
-            var stackTrace = e.stackTrace.toString();
+          var trace = getAttachedStackTrace(error);
+          if (trace != null) {
+            var stackTrace = trace.toString();
             stackTrace = "  ${stackTrace.replaceAll("\n", "\n  ")}";
             reason = "Actual exception trace:\n$stackTrace";
           }
-          expect(e.error, _matcher, reason: reason);
+          expect(error, _matcher, reason: reason);
         });
       });
       // It hasn't failed yet.
       return true;
     }
 
     try {
       item();
       return false;
     } catch (e, s) {
@@ skipping 373 matching lines @@
       description.add(_featureDescription).add(' ').addDescriptionOf(_matcher);
 
   Description describeMismatch(item, Description mismatchDescription,
                                MatchState matchState, bool verbose) {
     mismatchDescription.add(_featureName).add(' ');
     _matcher.describeMismatch(matchState.state['feature'], mismatchDescription,
         matchState.state['innerState'], verbose);
     return mismatchDescription;
   }
 }