Issue #3295625 by longwave, catch: Remove deprecated code from FormattableMarkup

          break;

        default:

          // Deprecate support for random variables that won't be replaced.

          if (ctype_alpha($key[0]) && strpos($string, $key) === FALSE) {

            @trigger_error(sprintf('Support for keys without a placeholder prefix is deprecated in Drupal 9.1.0 and will be removed in Drupal 10.0.0. Invalid placeholder (%s) with string: "%s"', $key, $string), E_USER_DEPRECATED);

          }

          else {

          // Warn for random variables that won't be replaced.

          trigger_error(sprintf('Invalid placeholder (%s) with string: "%s"', $key, $string), E_USER_WARNING);

          }

          // No replacement possible therefore we can discard the argument.

          unset($args[$key]);

          break;

      // Ensure that where the placeholder is located in the string is

      // irrelevant.

      ['placeholder', ['placeholder' => 'replaced'], E_USER_WARNING, 'Invalid placeholder (placeholder) with string: "placeholder"'],

      ['No replacements', ['foo' => 'bar'], E_USER_WARNING, 'Invalid placeholder (foo) with string: "No replacements"'],

    ];

  }

  /**

   * @group legacy

   */

  public function testNoReplacementUnsupportedVariable() {

    $this->expectDeprecation('Support for keys without a placeholder prefix is deprecated in Drupal 9.1.0 and will be removed in Drupal 10.0.0. Invalid placeholder (foo) with string: "No replacements"');

    $markup = new FormattableMarkup('No replacements', ['foo' => 'bar']);

    // Cast it to a string which will generate the deprecation notice.

    $output = (string) $markup;

  }

}