anchor.diff:      'name': name,
       'qualifiedName': qualifiedName,
       'comment': comment,
  +    'isAbstract' : isAbstract,
       'superclass': validSuperclass(),
       'implements': interfaces.where(_isVisible)
           .map((e) => e.qualifiedName).toList(),
  
positive.code: 
      clazz.ensureComments();
  
      if (isError(mirror.qualifiedName)) {
        errors[mirror.simpleName] = clazz;
      } else if (mirror.isTypedef) {
        if (_includePrivate || !mirror.isPrivate) {
  
negative.code:  * classes, regular classes, typedefs, and errors.
   */
  class ClassGroup {
    Map<String, Class> classes = {};
    Map<String, Typedef> typedefs = {};
    Map<String, Class> errors = {};
  
  