anchor.diff:  
       List<Source> sources = [];
   
  -    files.forEach((String filePath) {
  +    void processLibrary(String filePath) {
         String name = filePath;
         if (name.startsWith(Directory.current.path)) {
           name = name.substring(Directory.current.path.length);
  
positive.code:         LibraryElement library = context.computeLibraryElement(source);
          libraries.add(library);
        }
      });
  
      // Ensure that the analysis engine performs all remaining work.
      AnalysisResult result = context.performAnalysisTask();
  
negative.code:     PackageMapInfo packageMapInfo =
          pubPackageMapProvider.computePackageMap(cwd);
      Map<String, List<fileSystem.Folder>> packageMap = packageMapInfo.packageMap;
      EmbedderUriResolver embedderUriResolver;
      if (packageMap != null) {
        resolvers.add(new SdkExtUriResolver(packageMap));
        resolvers.add(new PackageMapUriResolver(
            PhysicalResourceProvider.INSTANCE, packageMap));
  
        embedderUriResolver = new EmbedderUriResolver(
            new EmbedderYamlLocator(packageMap).embedderYamls);
        if (embedderUriResolver.length == 0) {
          // The embedder uri resolver has no mappings. Use the default Dart SDK
  