anchor.diff:      ..isAbstract = true;
     builder.superTypes.add(classifier);
     builder.properties
  -    ..add((new PropertyBuilder()
  -          ..name = 'genericTypes'
  -          ..type = _createBuiltSet(typeParameter))
  -        .build());
  +    ..add(new Property((b) => b
  +      ..name = 'genericTypes'
  +      ..type = _createBuiltSet(typeParameter)));
   
     return builder.build();
   }
  
positive.code:     ..isAbstract = true;
    builder.superTypes.add(modelElement);
    builder.properties
      ..add((new PropertyBuilder()
            ..name = 'name'
            ..type = dartString)
          .build());
  
    return builder.build();
  }
  
negative.code: exist yet''';
    builder.superTypes.add(genericClassifier);
    builder.properties
      ..add(new Property((b) => b
        ..name = 'properties'
        ..type = _createBuiltSet(property)))
      ..add(new Property((b) => b
        ..name = 'allProperties'
        ..type = _createBuiltSet(property)
        ..derivedExpression = '''new BuiltSet<Property>(
      concat([superTypes.expand((vc) => vc.allProperties), properties]))'''))
      ..add(new Property((b) => b
        ..name = 'isAbstract'
        ..type = dartBool
        ..defaultValue = false));
    return builder.build();
  }
  
  