anchor.diff:      _length++;
     }
   
  -  void _unlink(E entry) {
  +  void _unlink(LinkedListEntry<E> entry) {
       _modificationCount++;
       entry._next._previous = entry._previous;
       entry._previous._next = entry._next;
  
positive.code:     _modificationCount++;
      _LinkedListLink next = _next;
      while (!identical(next, this)) {
        _LinkedListLink entry = next;
        next = entry._next;
        entry._next = entry._previous = entry._list = null;
      }
  
negative.code:    */
    void forEach(void action(E entry)) {
      int modificationCount = _modificationCount;
      E current = _next;
      while (!identical(current, this)) {
        action(current);
        if (modificationCount != _modificationCount) {
  