anchor.diff:  }
   
   /**
  - * Used to mark scope exit with a value
  + * Used to mark scope exit with a value. [scope] is the return value of a call
  + * to [enter]. Return values only work if WTF has been enabled.
    */
  -dynamic leaveVal(scope, returnValue) {
  +void leaveVal(scope, returnValue) {
     if (wtfEnabled) {
       _arg2[0] = scope;
       _arg2[1] = returnValue;
  
positive.code:   return null;
  }
  
  dynamic endAsync(dynamic range) {
    if (wtfEnabled) {
      _arg1[0] = range;
      return _endTimeRange.apply(_arg1, thisArg: _trace);
    }
    return null;
  }
  
negative.code: }
  
  /**
   * Used to mark scope entry. The return value is used to leave the scope.
   *
   *     final myScope = createScope('myMethod');
   *
  