anchor.diff:  
     Iterator<E> get iterator => new _LinkedListIterator<E>(this);
   
  -  // TODO(zarah) Remove this, and let it be inherited by IterableMixin
  -  String toString() => IterableMixinWorkaround.toStringIterable(this, '{', '}');
  -
     int get length => _length;
   
  +  /**
  +   * Remove all elements from this linked list.
  +   */
     void clear() {
       _modificationCount++;
       _LinkedListLink next = _next;
  
positive.code: 
  
  /**
   * Entry element for a [LinkedList]. Any entry must extend this class.
   */
  abstract class LinkedListEntry<E extends LinkedListEntry<E>>
      implements _LinkedListLink {
  
negative.code:   }
  
    /**
     * Call [action] with each entry in this linked list.
     *
     * It's an error if [action] modify the linked list.
     */
    void forEach(void action(E entry)) {
      int modificationCount = _modificationCount;
  