code: func (t *tree) parseAutoescape(attrs map[string]string) ast.AutoescapeType {
  	switch val := attrs["autoescape"]; val {
  	case "":
  		return ast.AutoescapeUnspecified
  	case "contextual":
  		return ast.AutoescapeContextual
  	case "deprecated-contextual":
  		return ast.AutoescapeContextual
  	case "true":
  		return ast.AutoescapeOn
  	case "false":
  		return ast.AutoescapeOff
  	default:
  		t.errorf(`expected "true", "false", or "contextual" for autoescape, got %q`, val)
  	}
  	panic("unreachable")
  }
docs: // parseAutoescape returns the specified autoescape selection, or
  // AutoescapeContextual by default.