anchor.diff:        }
         List <_Node<K, V>> array = [];
         int bitmap=0;
  -      for (int i=0; i<32; i++){
  +      for (int i=0; i<branching; i++){
             if (kvs[i] != null) {
             bitmap |= 1<<i;
             assert(kvs[i].length % recsize == 0);
  
positive.code:     if (_kv.length < recsize*leafSize) {
        return new _Leaf.abc(owner, _kv, _kv.length ~/ recsize);
      } else {
        List<List> kvs = new List.filled(32, null);
        for (int i=0; i<_kv.length; i+=recsize){
  //        var key = _kv[i];
  //        var val = _kv[i + 1];
  //        var hash = _kv[i + 2];
          int branch = (_kv[i+2] >> (depth * 5)) & 0x1f;
          if (kvs[branch] == null){
            kvs[branch] = [];
          }
  
negative.code: 
  
    _Node<K, V> _delete(owner, K key, int hash, int depth, bool missingOk) {
      int branch = (hash >> (depth * branchingBits)) & branchingMask;
      int mask = 1 << branch;
  
      if ((_bitmap & mask) != 0) {
  