Abort earlier on compilation errors

dart/lib/compiler/implementation/resolver.dart

Index: dart/lib/compiler/implementation/resolver.dart
diff --git a/dart/lib/compiler/implementation/resolver.dart b/dart/lib/compiler/implementation/resolver.dart
index 9bb919a1b08c3c29135899fcbc628f782278bd42..405de6872c4655b58f2f636d4173cf4956a6da9c 100644
--- a/dart/lib/compiler/implementation/resolver.dart
+++ b/dart/lib/compiler/implementation/resolver.dart
@@ -237,6 +237,8 @@ class ResolverTask extends CompilerTask {
         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;