anchor.diff:  
   final _multilineRx = new RegExp(r'^.*?$', multiLine: true);
   
  -SourceLocation computeSourceSpan(String content, String sourceUrl, int line, int column) {
  +SourceLocation _computeSourceSpan(String content, String sourceUrl, int line, int column) {
     int nextLine = 1;
     for (var match in _multilineRx.allMatches(content)) {
       if (line == nextLine) {
  
positive.code:      String sasscPath: 'sassc',
       List<String> sasscArgs: const<String>[]}) async {
  
    var sassId = sassAsset.id;
    var sassContent = sassAsset.readAsString();
    var dir = await Directory.systemTemp.createTemp();
  
negative.code:       relative(cssFile.path, from: dir.path)
      ]..addAll(sasscArgs);
      cmd = [sasscPath]..addAll(args);
      var result = await Process.run(sasscPath, args, workingDirectory: dir.path);
  
      var messages = <SassMessage>[];
  