Isolate.spawn{Uri} only reports errors asynchronously.

runtime/lib/schedule_microtask_patch.dart

 // Copyright (c) 2013, 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.
 
-patch class _AsyncRun {
-  /* patch */ static void _scheduleImmediate(void callback()) {
-    if (_ScheduleImmediate._closure == null) {
-      // TODO(9001): don't default to using the Timer to enqueue the immediate
-      //             callback.
-      _createTimer(Duration.ZERO, callback);
-      return;
-    }
-    _ScheduleImmediate._closure(callback);
+@deprecated

[Lasse Reichstein Nielsen, 2013/11/27 11:41:28]

Why deprecate this and add another?
Can we just keep this one?

[floitsch, 2013/11/27 13:57:06]

No.
This one is not in _collection-dev.
The only reason it is still here is, to have a smooth transition for the Dartium
bindings that set this closure instead of setting the one in _collection-dev.
I have already a patch for it, and we can then remove this one.
https://chromiumcodereview.appspot.com/85333004/

+class _ScheduleImmediate {
+  static set _closure(closure) {
+    scheduleImmediateClosure = closure;
   }
 }
-
-typedef void _ScheduleImmediateClosure(void callback());
-
-class _ScheduleImmediate {
-  static _ScheduleImmediateClosure _closure;
-}
-
-void _setScheduleImmediateClosure(_ScheduleImmediateClosure closure) {
-  _ScheduleImmediate._closure = closure;
-}