anchor.diff:    bool containsKey(String name) {
       return classes.containsKey(name) || errors.containsKey(name);
     }
  -
  -  /**
  -   * Creates a [Map] with [Class] names and a preview comment.
  -   */
  -  Map classMap(Class clazz) {
  -    var finalMap = { 'name' : clazz.qualifiedName };
  -    if (clazz.comment != '') {
  -      var index = clazz.comment.indexOf('</p>');
  -      finalMap['preview'] = '${clazz.comment.substring(0, index)}</p>';
  -    }
  -    return finalMap;
  -  }
     
     Map toMap() => {
       'class': classes.values.where(_isVisible)
  -      .map((e) => classMap(e)).toList(),
  +      .map((e) => e.previewMap).toList(),
       'typedef': recurseMap(typedefs),
       'error': errors.values.where(_isVisible)
  -      .map((e) => classMap(e)).toList()
  +      .map((e) => e.previewMap).toList()
     };
   }
   
  
positive.code:   filteredEntities.where((e) => e is Class || e is Library).forEach((output) {
      _writeIndexableToFile(output, outputToYaml);
    });
    // Outputs a text file with a list of libraries available after creating all
    // the libraries. This will help the viewer know what libraries are available
    // to read in.
    _writeToFile(filteredEntities.where((e) => e is Library)
        .map((e) => e.qualifiedName).join('\n'), 'library_list.txt',
        append: append);
    // Outputs all the qualified names documented with their type.
    // This will help generate search results.
    _writeToFile(filteredEntities.map((e) => 
  
negative.code:   
    /// The type of this member to be used in index.txt.
    String get typeName => '';
    
    /**
     * Creates a [Map] with this [Indexable]'s name and a preview comment.
     */
    Map get previewMap {
      var finalMap = { 'name' : qualifiedName };
      if (comment != '') {
        var index = comment.indexOf('</p>');
        finalMap['preview'] = '${comment.substring(0, index)}</p>';
      }
      return finalMap;
    }
  }
  
  /**
  