anchor.diff:  // Copyright (c) 2012, Lukas Renggli <renggli@gmail.com>
  +
  +/** Function interface for parse actions. */
  +typedef Dynamic Action(Dynamic argument);
   
   /**
    * A parser that performs a transformation with a given function on the
  
positive.code:  */
  class ActionParser extends DelegateParser {
  
    final Function _function;
  
    ActionParser(parser, this._function) : super(parser);
  
  
negative.code:   final int _start;
    final int _stop;
  
    const Token(this._buffer, this._start, this._stop);
  
    bool operator == (Token other) => other is Token
        && _buffer === other._buffer
  