Remove AsyncError with Expando.

sdk/lib/async/stream_controller.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 dart.async;
 
 // -------------------------------------------------------------------
 // Controller for creating and adding events to a stream.
 // -------------------------------------------------------------------
 
@@ skipping 93 matching lines @@
   bool get hasListener => stream._hasListener;
 
   /**
    * Send or queue a data event.
    */
   void add(T value) => stream._add(value);
 
   /**
    * Send or enqueue an error event.
    *
-   * If [error] is not an [AsyncError], [error] and an optional [stackTrace]
-   * is combined into an [AsyncError] and sent this stream's listeners.
-   *
-   * Otherwise, if [error] is an [AsyncError], it is used directly as the
-   * error object reported to listeners, and the [stackTrace] is ignored.
-   *
    * If a subscription has requested to be unsubscribed on errors,
    * it will be unsubscribed after receiving this event.
    */
   void addError(Object error, [Object stackTrace]) {
-    AsyncError asyncError;
-    if (error is AsyncError) {
-      asyncError = error;
-    } else {
-      asyncError = new AsyncError(error, stackTrace);
+    if (stackTrace != null) {
+      // Force stack trace overwrite. Even if the error already contained
+      // a stack trace.
+      _attachStackTrace(error, stackTrace);
     }
-    stream._addError(asyncError);
+    stream._addError(error);
   }
 
   /**
    * Send or enqueue a "done" message.
    *
    * The "done" message should be sent at most once by a stream, and it
    * should be the last message sent.
    */
   void close() { stream._close(); }
 }
 
 typedef void _NotificationHandler();
 
 class _MultiControllerStream<T> extends _MultiStreamImpl<T> {
   _NotificationHandler _subscriptionHandler;
   _NotificationHandler _pauseHandler;
 
   _MultiControllerStream(this._subscriptionHandler, this._pauseHandler);
 
   void _onSubscriptionStateChange() {
     if (_subscriptionHandler != null) {
       try {
         _subscriptionHandler();
       } catch (e, s) {
-        new AsyncError(e, s).throwDelayed();
+        _throwDelayed(e, s);
       }
     }
   }
 
   void _onPauseStateChange() {
     if (_pauseHandler != null) {
       try {
         _pauseHandler();
       } catch (e, s) {
-        new AsyncError(e, s).throwDelayed();
+        _throwDelayed(e, s);
       }
     }
   }
 }
 
 class _SingleControllerStream<T> extends _SingleStreamImpl<T> {
   _NotificationHandler _subscriptionHandler;
   _NotificationHandler _pauseHandler;
 
   _SingleControllerStream(this._subscriptionHandler, this._pauseHandler);
 
   void _onSubscriptionStateChange() {
     if (_subscriptionHandler != null) {
       try {
         _subscriptionHandler();
       } catch (e, s) {
-        new AsyncError(e, s).throwDelayed();
+        _throwDelayed(e, s);
       }
     }
   }
 
   void _onPauseStateChange() {
     if (_pauseHandler != null) {
       try {
         _pauseHandler();
       } catch (e, s) {
-        new AsyncError(e, s).throwDelayed();
+        _throwDelayed(e, s);
       }
     }
   }
 }