anchor.diff:    /**
      * If result not found, always chose the smaler element
      */
  -  static const LESS_THAN = const TreeSearch(1);
  +  static const LESS_THAN = const TreeSearch._(1);
   
     /**
      * If result not found, chose the nearest based on comparison
      */
  -  static const NEAREST = const TreeSearch(2);
  +  static const NEAREST = const TreeSearch._(2);
   
     /**
      * If result not found, always chose the greater element
      */
  -  static const GREATER_THAN = const TreeSearch(3);
  +  static const GREATER_THAN = const TreeSearch._(3);
   
     final int _val;
  -  const TreeSearch(this._val);
  +  const TreeSearch._(this._val);
   }
   
   
  
positive.code:   TreeSet._(this.comparator);
  
    /**
     * Returns an Iterator that iterates over this tree, in reverse.
     */
    Iterator<V> get reversed;
  
  
    /**
     * Search the tree for the matching [object] or the [nearestOption]
  
negative.code:  */
  class AvlNode<V> extends TreeNode<V> {
  
    AvlNode<V> left;
    AvlNode<V> right;
  
    //TODO(codefu): Remove need for [parent]; this is just an implementation note
    AvlNode<V> parent;
  
    AvlNode({AvlNode left: null, AvlNode right: null,
        AvlNode parent: null, V object, this.balanceFactor: 0}) :
        super(left: left, right: right, parent: parent, object: object);
  