Don't wait unnecessarily.

corelib/src/promise.dart

 // Copyright (c) 2011, 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.
 
 // Dart core library.
 
 /** A promise to value of type [T] that may be computed asynchronously. */
 interface Promise<T> factory PromiseImpl<T> {
 
   Promise();
@@ skipping 62 matching lines @@
    * flatten returns a Promise<T>.
    */
   Promise flatten();
 
   /**
    * Mark this promise as complete when some or all values in [arr] are
    * computed. Every time one of the promises is computed, it is passed to
    * [joinDone]. When [joinDone] returns true, this instance is marked as
    * complete with the last value that was computed.
    */
-  void join(Collection<Promise<T>> arr, bool joinDone(Promise<T> completed));
+  void join(Collection<Promise> arr, bool joinDone(Promise completed));
 
   /**
    * Mark this promise as complete when [n] promises in [arr] complete, then
    * cancel the rest of the promises in [arr] that didn't complete.
    */
   void waitFor(Collection<Promise> arr, int n);
 }
 
 
-interface Proxy factory ProxyImpl {
+interface Proxy extends Promise<bool> factory ProxyImpl {
 
   Proxy.forPort(SendPort port);
   Proxy.forIsolate(Isolate isolate);
   Proxy._forIsolateWithPromise(Isolate isolate, Promise<SendPort> promise);
   /*
    * The [Proxy.forReply] constructor is used to create a proxy for
    * the object that will be the reply to a message send.
    */
   Proxy.forReply(Promise<SendPort> port);
 
   void send(List message);
+  Promise call(List message);
 
 }
 
 
 class ProxyImpl extends ProxyBase implements Proxy {
 
   ProxyImpl.forPort(SendPort port)
       : super.forPort(port) { }
 
   ProxyImpl.forIsolate(Isolate isolate)
@@ skipping 54 matching lines @@
   PromiseProxy(Promise<SendPort> sendCompleter) {
     ReceivePort completer = new ReceivePort.singleShot();
     completer.receive((var msg, SendPort _) {
       complete(msg[0]);
     });
     sendCompleter.addCompleteHandler((SendPort port) {
       port.send([completer.toSendPort()], null);
     });
   }
 }