anchor.diff:    }
   
     BaseVectorImpl _ensureOwner(Owner ownerID) {
  -    if (ownerID == this.__ownerID) {
  +    if (ownerID == this._owner) {
         return this;
       }
       if (ownerID == null) {
  -      this.__ownerID = ownerID;
  +      this._owner = ownerID;
         return new PersistentVectorImpl._make(this._origin, this._size, this._level, this._root, this._tail);
       }
       return new TransientVectorImpl._make(this._origin, this._size, this._level, this._root, this._tail, ownerID);
     }
   
     TransientVectorImpl _asMutable() {
  -    return this.__ownerID != null ? this : this._ensureOwner(new Owner());
  +    return this._owner != null ? this : this._ensureOwner(new Owner());
     }
   
     PersistentVectorImpl _asImmutable() {
  
positive.code:       throw new RangeError.value(end);
      }
      var owner;
      if (__ownerID == null) {
        owner = __ownerID;
      } else {
        owner = new Owner();
      }
      //var owner = __ownerID || new Owner();
      var oldSize = _size;
      var newSize = end;
  
  
negative.code:       newTail = newTail._removeAfter(owner, 0, newSize);
      }
  
      if (_owner != null) {
        _size = newSize;
        _origin = 0;
        _level = newLevel;
  