anchor.diff:  
     @override
     void set identifier(SimpleIdentifier identifier) {
  -    _identifier = _becomeParentOf(identifier as AstNodeImpl);
  +    _identifier = _becomeParentOf(identifier as SimpleIdentifierImpl);
     }
   
     @deprecated
  
positive.code:    * [metadata] can be `null` if the directive does not have the corresponding
     * attribute.
     */
    DirectiveImpl(Comment comment, List<Annotation> metadata)
        : super(comment, metadata);
  
    @override
  
negative.code:   /**
     * The name of the parameter being declared.
     */
    SimpleIdentifierImpl _identifier;
  
    /**
     * Initialize a newly created formal parameter. Either or both of the
  