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