Fix deferred load errors / bug #26482

runtime/lib/lib_prefix.dart

 // Copyright (c) 2014, 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.
 
 import "dart:async";
 import "dart:isolate";
 
 // This type corresponds to the VM-internal class LibraryPrefix.
 class _LibraryPrefix {
   bool _load() native "LibraryPrefix_load";
   Error _loadError() native "LibraryPrefix_loadError";
   bool isLoaded() native "LibraryPrefix_isLoaded";
+  bool hasError() native "LibraryPrefix_hasError";
   bool _invalidateDependentCode()
       native "LibraryPrefix_invalidateDependentCode";
 
   loadLibrary() {
     for (int i = 0; i < _outstandingLoadRequests.length; i++) {
       if (_outstandingLoadRequests[i][0] == this) {
         return _outstandingLoadRequests[i][1].future;
       }
     }
 
@@ skipping 25 matching lines @@
 
 // Called from the VM when an outstanding load request has finished.
 _completeDeferredLoads() {
   // Determine which outstanding load requests have completed and complete
   // their completer (with an error or true). For outstanding load requests
   // which have not completed, remember them for next time in
   // stillOutstandingLoadRequests.
   var stillOutstandingLoadRequests = new List<List>();
   for (int i = 0; i < _outstandingLoadRequests.length; i++) {
     var prefix = _outstandingLoadRequests[i][0];
-    if (prefix._load()) {
-      var completer = _outstandingLoadRequests[i][1];
+    var completer = _outstandingLoadRequests[i][1];
+    if (prefix.hasError()) {

[hausner, 2016/06/07 21:47:05]

I think you should use prefix._loadError() to determine whether there was an
error while loading. That function checks the library import graph transitively
for errors. 

[Cutch, 2016/06/07 22:29:26]

Done.

       var error = prefix._loadError();
-      if (error != null) {
-        completer.completeError(error);
-      } else {
-        prefix._invalidateDependentCode();
-        completer.complete(true);
-      }
+      assert(error != null);
+      completer.completeError(error);
+    } else if (prefix._load()) {
+      prefix._invalidateDependentCode();
+      completer.complete(true);
     } else {
       stillOutstandingLoadRequests.add(_outstandingLoadRequests[i]);
     }
   }
   _outstandingLoadRequests = stillOutstandingLoadRequests;
 }