anchor.diff:      int previousIndex = 0;
       while (true) {
         if (startIndex == length || !iterator.hasNext) {
  -        result.add(this.substring(previousIndex, length));
  +        result.add(this._substringUnchecked(previousIndex, length));
           break;
         }
         Match match = iterator.next();
         if (match.start == length) {
  -        result.add(this.substring(previousIndex, length));
  +        result.add(this._substringUnchecked(previousIndex, length));
           break;
         }
         int endIndex = match.end;
  
positive.code:       ((9 <= codePoint) && (codePoint <= 13)); // CR, LF, TAB, etc.
    }
  
    String _substringUnchecked(int startIndex, int endIndex)
        native "OneByteString_substringUnchecked";
  }
  
  
negative.code:   }
  
    bool operator ==(Object other) {
      if (identical(this, other)) {
        return true;
      }
      if ((other is !String) ||
  