anchor.diff:     * Initialize a newly created with clause.
      */
     WithClauseImpl(this.withKeyword, List<TypeName> mixinTypes) {
  -    _mixinTypes = new NodeList<TypeName>(this, mixinTypes);
  +    _mixinTypes = new NodeListImpl<TypeName>(this, mixinTypes);
     }
   
     @override
  
positive.code:     _variableList = _becomeParentOf(variableList);
      _initialization = _becomeParentOf(initialization);
      _condition = _becomeParentOf(condition);
      _updaters = new NodeList<Expression>(this, updaters);
      _body = _becomeParentOf(body);
    }
  
  
negative.code:    * Initialize a newly created implements clause.
     */
    ImplementsClauseImpl(this.implementsKeyword, List<TypeName> interfaces) {
      _interfaces = new NodeListImpl<TypeName>(this, interfaces);
    }
  
    @override
  