anchor.diff:    }
   
     void visitString(SassString string) {
  -    _buffer.write(string.hasQuotes
  -        ? _visitString(string.text)
  -        : string.text.replaceAll("\n", " "));
  -  }
  -
  -  String _visitString(String string, {bool forceDoubleQuote: false}) {
  +    if (string.hasQuotes) {
  +      _visitString(string.text);
  +    } else {
  +      _buffer.write(string.text.replaceAll("\n", " "));
  +    }
  +  }
  +
  +  void _visitString(String string, {bool forceDoubleQuote: false}) {
       var includesSingleQuote = false;
       var includesDoubleQuote = false;
  -    var buffer = new StringBuffer();
  +
  +    var buffer = forceDoubleQuote ? _buffer : new StringBuffer();
  +    if (forceDoubleQuote) buffer.writeCharCode($double_quote);
       for (var i = 0; i < string.length; i++) {
         var char = string.codeUnitAt(i);
         switch (char) {
  
positive.code:             buffer.writeCharCode($backslash);
              buffer.writeCharCode($double_quote);
            } else if (includesSingleQuote) {
              return _visitString(string, forceDoubleQuote: true);
            } else {
              includesDoubleQuote = true;
              buffer.writeCharCode($double_quote);
  
negative.code:       }
      }
  
      if (forceDoubleQuote) {
        buffer.writeCharCode($double_quote);
      } else {
        var quote = includesDoubleQuote ? $single_quote : $double_quote;
        _buffer.writeCharCode(quote);
        _buffer.write(buffer);
        _buffer.writeCharCode(quote);
      }
    }
  
    // ## Selectors
  