Non fatal errors on duplicated accessors

dart/pkg/compiler/lib/src/resolution/members.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.
 
 part of resolution;
 
 abstract class TreeElements {
   AnalyzableElement get analyzedElement;
   Iterable<Node> get superUses;
 
@@ skipping 1101 matching lines @@
     // field once, so we just ignore setters.
     if (!member.isGetter) return;
 
     // Find the associated abstract field.
     ClassElement classElement = member.enclosingClass;
     Element lookupElement = classElement.lookupLocalMember(member.name);
     if (lookupElement == null) {
       compiler.internalError(member,
           "No abstract field for accessor");
     } else if (!identical(lookupElement.kind, ElementKind.ABSTRACT_FIELD)) {
+      if (lookupElement.isErroneous || lookupElement.isAmbiguous) return;
       compiler.internalError(member,
           "Inaccessible abstract field for accessor");
     }
     AbstractFieldElement field = lookupElement;
 
     FunctionElementX getter = field.getter;
     if (getter == null) return;
     FunctionElementX setter = field.setter;
     if (setter == null) return;
     int getterFlags = getter.modifiers.flags | Modifiers.FLAG_ABSTRACT;
@@ skipping 3882 matching lines @@
 }
 
 /// The result for the resolution of the `assert` method.
 class AssertResult implements ResolutionResult {
   const AssertResult();
 
   Element get element => null;
 
   String toString() => 'AssertResult()';
 }