Abort earlier on compilation errors

dart/lib/compiler/implementation/resolver.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.
 
 interface TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   Type getType(TypeAnnotation annotation);
 }
 
@@ skipping 219 matching lines @@
     compiler.withCurrentElement(cls, () => measure(() {
       if (cls.supertypeLoadState == ClassElement.STATE_DONE) return;
       if (cls.supertypeLoadState == ClassElement.STATE_STARTED) {
         compiler.reportMessage(
           compiler.spanFromNode(from),
           MessageKind.CYCLIC_CLASS_HIERARCHY.error([cls.name]),
           api.Diagnostic.ERROR);
         cls.supertypeLoadState = ClassElement.STATE_DONE;
         cls.allSupertypes = const EmptyLink<Type>().prepend(
             compiler.objectClass.computeType(compiler));
+        // TODO(ahe): We should also set cls.supertype here to avoid
+        // creating a malformed class hierarchy.
         return;
       }
       cls.supertypeLoadState = ClassElement.STATE_STARTED;
       compiler.withCurrentElement(cls, () {
         // TODO(ahe): Cache the node in cls.
         cls.parseNode(compiler).accept(new ClassSupertypeResolver(compiler,
                                                                   cls));
         if (cls.supertypeLoadState != ClassElement.STATE_DONE) {
           cls.supertypeLoadState = ClassElement.STATE_DONE;
         }
@@ skipping 2147 matching lines @@
   TopScope(LibraryElement library) : super(null, library);
   Element lookup(SourceString name) {
     return library.find(name);
   }
 
   Element add(Element newElement) {
     throw "Cannot add an element in the top scope";
   }
   String toString() => '$element';
 }