anchor.diff:          }
           LibraryElement library = await compiler.analyzeUri(file);
           if (library != null) {
  +          if (library.libraryName == 'dart2js.helpers') {
  +            helperLibrary = library;
  +          }
             library.forEachLocalMember((Element element) {
               if (element is ClassElement) {
                 element.forEachLocalMember((AstElement member) {
  
positive.code: 
    bool isHelper(Element element) {
      Uri uri = element.library.canonicalUri;
      return '$uri'.startsWith('package:compiler/src/helpers/');
    }
  
    void checkAccess(Node node, MemberElement element) {
  
negative.code: 
    AnalyzableElement get analyzedElement => resolvedAst.element;
  
    HelperAnalyzer(this.diagnostics, this.helpersUriPrefix) : super(null);
  
    @override
    void apply(Node node, [_]) {
  