anchor.diff:      library.setExports(library.localScope.values.toList());
       registerSource(uri, source);
       libraries.putIfAbsent(uri.toString(), () => library);
  -    return new Future.value(library);
  +    return library;
     }
   
     void reportWarning(Node node, var message) {
  
positive.code:    * Used internally to create a library from a source text. The created library
     * is fixed to export its top-level declarations.
     */
    Future<LibraryElement> createLibrary(String name, String source) {
      Uri uri = new Uri(scheme: "dart", path: name);
      var script = new Script(uri, new MockFile(source));
      var library = new LibraryElementX(script);
  
negative.code:               analyzeOnly: analyzeOnly,
                emitJavaScript: emitJavaScript,
                preserveComments: preserveComments) {
      coreLibrary = createLibrary("core", coreSource);
  
      // We need to set the assert method to avoid calls with a 'null'
      // target being interpreted as a call to assert.
      jsHelperLibrary = createLibrary("helper", helperSource);
      foreignLibrary = createLibrary("foreign", FOREIGN_LIBRARY);
      interceptorsLibrary = createLibrary("interceptors", interceptorsSource);
      isolateHelperLibrary = createLibrary("isolate_helper", isolateHelperSource);
  
      // Set up the library imports.
      importHelperLibrary(coreLibrary);
  