anchor.diff:  
       cursor.skip = skip;
       cursor.limit = limit;
  -        
  +    
  +    var sc = new StreamController();
  +    
       return cursor.stream.asyncMap((m) {
         if(!_known.containsKey(m["_id"])) {
           var obj = _dty.mirror.newInstance(#revive, [m]).reflectee;
  
positive.code:   
    @override
    Future close() {
      return _conn.close().then((_) {
        _conn = null;
      });
    }
  }
  
  
negative.code:       } else {
          // Explicitly *DONT* override members here to avoid clobbering unsaved
          // changes
          return _known[m["_id"]];
        }
      });
  