anchor.diff:     */
     bool get isNotEmpty => !isEmpty;
   
  -   /**
  +  /**
      * Returns a lazy iterable of the [count] first elements of this iterable.
      *
      * The returned `Iterable` may contain fewer than `count` elements, if `this`
  
positive.code:    * function is returned.
     * If [orElse] is omitted, it defaults to throwing a [StateError].
     */
    E firstWhere(bool test(E element), { E orElse() }) {
      for (E element in this) {
        if (test(element)) return element;
      }
  
negative.code:     E result;
      do {
        result = it.current;
      } while (it.moveNext());
      return result;
    }
  
  