anchor.diff:    throw new StateError("No such position in file: line $line, column $column");
   }
   
  +String _resolveEnvVars(String s) =>
  +    s.replaceAllMapped(
  +        new RegExp(r'\$\{([^}]+)\}'),
  +        (Match m) => (Platform.environment[m.group(1)] ?? ''));
  +
   // _normalize(String path) {
   //   while (true) {
   //     var newPath = path.replaceAll(new RegExp(r'\.\./\.?[^./]+/|(^|/)\./'), '');
  
positive.code: 
  final _multilineRx = new RegExp(r'^.*?$', multiLine: true);
  
  SourceLocation computeSourceSpan(String content, String sourceUrl, int line, int column) {
    int nextLine = 1;
    for (var match in _multilineRx.allMatches(content)) {
      if (line == nextLine) {
  
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>[];
  