anchor.diff:    factory PersistentVectorImpl.empty() => new PersistentVectorImpl._prototype();
     PersistentVectorImpl._prototype() : super._prototype();
   
  -  factory PersistentVectorImpl._make(int origin, int size, int level, _VNode root, _VNode tail) {
  +  factory PersistentVectorImpl._make(int size, int level, _VNode root, _VNode tail) {
       var x = new PersistentVectorImpl._prototype();
  -    x._origin = origin;
       x._size = size;
       x._level = level;
       x._root = root;
  
positive.code:   }
  
    TransientVectorImpl _clear() {
      this._size = 0;
      this._origin = 0;
      this._level = _SHIFT;
      this._root = this._tail = null;
      this._hashCode = null;
  
negative.code: class TransientVectorImpl<E> extends BaseVectorImpl<E> implements TransientVector<E> {
    TransientVectorImpl._prototype() : super._prototype();
  
    factory TransientVectorImpl._make(int size, int level, _VNode root, _VNode tail, Owner ownerID) {
      var x = new TransientVectorImpl._prototype();
      x._size = size;
      x._level = level;
      x._root = root;
  