anchor.diff:      return new _Leaf.abc(owner, kv);
     }
   
  -  /// creates either _Leaf with given _kv, or (if _kv.length is big enough) it
  -  /// splits the _kv to multiple _Nodes
  +  /// see technical.md for explanation of what this does
   
     _Node<K, V> _polish(_Owner owner, int depth, List _kv) {
       assert(_kv.length % recsize == 0);
  
positive.code:   }
  
    TMap<K, V> doDelete(K key, {bool missingOk: false}) {
      return _adjustRootAndReturn(_root._delete(owner, key, _reverseHash(key.hashCode), maxDepth, missingOk));
    }
  
    TMap<K, V> doUpdate(K key, dynamic updateF) {
  
negative.code: class _TMapImpl<K, V>
          extends IterableBase<Pair<K, V>>
          implements TMap<K, V> {
    // Although PMap can be represented a simple _Node, Transient map needs
    // separate structure with a mutable reference to _Node.
    _Node _root;
  
    _Owner _owner;
  