trait ToStringTrait in Drupal 8

trait ToStringTrait {

  /**
   * Implements the magic __toString() method.
   */
  public function __toString() {
    try {
      return (string) $this
        ->render();
    } catch (\Exception $e) {

      // User errors in __toString() methods are considered fatal in the Drupal
      // error handler.
      trigger_error(get_class($e) . ' thrown while calling __toString on a ' . get_class($this) . ' object in ' . $e
        ->getFile() . ' on line ' . $e
        ->getLine() . ': ' . $e
        ->getMessage(), E_USER_ERROR);

      // In case we are using another error handler that did not fatal on the
      // E_USER_ERROR, we terminate execution. However, for test purposes allow
      // a return value.
      return $this
        ->_die();
    }
  }

  /**
   * For test purposes, wrap die() in an overridable method.
   */
  protected function _die() {
    die;
  }

  /**
   * Renders the object as a string.
   *
   * @return string|object
   *   The rendered string or an object implementing __toString().
   */
  public abstract function render();

}