anchor.diff:      }
   
       if (newSize < oldSize) {
  -      newTail = newTail._removeAfter(owner, 0, newSize);
  +      newTail = newTail._removeAfter(owner, newSize);
       }
   
       if (_owner != null) {
  
positive.code:   _VNode _root;
    _VNode _tail;
    int _level;
    // cached hashCode.
    int _hashCode = null;
    bool __altered = false;
  
    BaseVectorImpl._prototype() {
  
negative.code: }
  
  class PersistentVectorImpl<E> extends BaseVectorImpl<E> implements PersistentVector<E> {
    // cached hashCode.
    int _hashCode = null;
  
  
    factory PersistentVectorImpl.from(Iterable<E> values) {
      if (values.length == 0) {
        return new PersistentVectorImpl.empty();
  