anchor.diff:        ..sourceFactory = sourceFactory;
   
       if (packageMeta.isSdk) {
  -      libraries.addAll(getSdkLibrariesToDocument(sdk, context));
  +      libraries
  +          .addAll(new Set()..addAll(getSdkLibrariesToDocument(sdk, context)));
       }
   
       List<Source> sources = [];
  
positive.code: 
  final String defaultOutDir = p.join('doc', 'api');
  
  /// Configure the dartdoc generation process
  void initializeConfig(
      {Directory inputDir,
      String sdkVersion,
      bool addCrossdart: false,
      bool includeSource: true}) {
    setConfig(
        inputDir: inputDir,
        sdkVersion: sdkVersion,
        addCrossdart: addCrossdart,
        includeSource: includeSource);
  }
  
  /// Initialize and setup the generators.
  Future<List<Generator>> initGenerators(String url, List<String> headerFilePaths,
      List<String> footerFilePaths, String relCanonicalPrefix,
  
negative.code:   ];
  }
  
  /// Configure the dartdoc generation process
  void initializeConfig(
      {Directory inputDir,
      String sdkVersion,
      bool addCrossdart: false,
      bool includeSource: true}) {
    setConfig(
        inputDir: inputDir,
        sdkVersion: sdkVersion,
        addCrossdart: addCrossdart,
        includeSource: includeSource);
  }
  
  /// Generates Dart documentation for all public Dart libraries in the given
  /// directory.
  class DartDoc {
  