code: func (f *file) firstLineOf(node, match ast.Node) string {
  	line := f.render(node)
  	if i := strings.Index(line, "\n"); i >= 0 {
  		line = line[:i]
  	}
  	return f.indentOf(match) + line
  }
docs: // firstLineOf renders the given node and returns its first line.
  // It will also match the indentation of another node.