anchor.diff:  /** Pads [source] to [length] by adding spaces at the end. */
   String padRight(String source, int length) {
     final result = new StringBuffer();
  -  result.add(source);
  +  result.write(source);
   
     while (result.length < length) {
  -    result.add(' ');
  +    result.write(' ');
     }
   
     return result.toString();
  -}+}
  
positive.code: 
    buildAllowedList(Option option) {
      var allowedBuffer = new StringBuffer();
      allowedBuffer.add('[');
      bool first = true;
      for (var allowed in option.allowed) {
        if (!first) allowedBuffer.add(', ');
        allowedBuffer.add(allowed);
        if (allowed == option.defaultValue) {
          allowedBuffer.add(' (default)');
        }
        first = false;
      }
      allowedBuffer.add(']');
      return allowedBuffer.toString();
    }
  }
  
negative.code:   writeLine(int column, String text) {
      // Write any pending newlines.
      while (newlinesNeeded > 0) {
        buffer.write('\n');
        newlinesNeeded--;
      }
  
  