anchor.diff:          ClassElement enclosingClass = element.getEnclosingClass();
           assert(enclosingClass.isClass());
           assert(enclosingClass.isTopLevel());
  -        addMemberToClass(element, enclosingClass);
  +        resolvedClassMembers
  +            .putIfAbsent(enclosingClass, () => new Set<Element>())
  +            .add(element);
           return;
         }
         if (!element.isTopLevel()) {
  
positive.code: 
    void processNativeClasses(Enqueuer world,
                              Collection<LibraryElement> libraries) {
    }
  
    /**
     * Adds given class element with its member element to resolved classes
     * collections.
     */
    void addMemberToClass(Element element, ClassElement classElement) {
      // ${element} should have ${classElement} as enclosing.
      assert(element.isMember());
      Set<Element> resolvedElementsInClass = resolvedClassMembers.putIfAbsent(
          classElement, () => new Set<Element>());
      resolvedElementsInClass.add(element);
    }
  
    void assembleProgram() {
  
negative.code:     Set<TypedefElement> typedefs = new Set<TypedefElement>();
      Set<ClassElement> classes = new Set<ClassElement>();
      Set<Element> elements = new Set<Element>();
      Map<ClassElement, Set<Element>> resolvedClassMembers =
          new Map<ClassElement, Set<Element>>();
      PlaceholderCollector collector = new PlaceholderCollector(compiler);
      resolvedElements.forEach((element, treeElements) {
        if (!shouldOutput(element)) return;
  