code: func (r SourceRange) StartString() string {
  	filename := r.Filename
  
  	// We'll try to relative-ize our filename here so it's less verbose
  	// in the common case of being in the current working directory. If not,
  	// we'll just show the full path.
  	wd, err := os.Getwd()
  	if err == nil {
  		relFn, err := filepath.Rel(wd, filename)
  		if err == nil {
  			filename = relFn
  		}
  	}
  
  	return fmt.Sprintf("%s:%d,%d", filename, r.Start.Line, r.Start.Column)
  }
docs: // StartString returns a string representation of the start of the range,
  // including the filename and the line and column numbers.