anchor.diff:  
   
   /**
  - * Entry element for a [LinkedList]. Any entry must extend this class.
  + * An object that can be an element in a [LinkedList].
  + *
  + * All elements of a `LinkedList` must extend this class.
  + * The class provides the internal links that link elements together
  + * in the `LinkedList`, and a reference to the linked list itself
  + * that an element is currently part of.
  + *
  + * An entry can be in at most one linked list at a time.
  + * While an entry is in a linked list, the [list] property points to that
  + * linked list, and otherwise the `list` property is `null`.
  + *
  + * When created, an entry is not in any linked list.
    */
   abstract class LinkedListEntry<E extends LinkedListEntry<E>>
       implements _LinkedListLink {
  
positive.code: 
    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;
  
    void clear() {
      _modificationCount++;
      _LinkedListLink next = _next;
  
negative.code:   }
  
    /**
     * Insert an element after this element in this element's linked list.
     *
     * This entry must be in a linked list when this method is called.
     * The [entry] must not be in a linked list.
     */
    void insertAfter(E entry) {
      _list._insertAfter(this, entry);
    }
  
    /**
     * Insert an element before this element in this element's linked list.
     *
     * This entry must be in a linked list when this method is called.
     * The [entry] must not be in a linked list.
     */
    void insertBefore(E entry) {
      _list._insertAfter(_previous, entry);
  