oldPath example

    $query = [
      'destination' => 'admin/structure/block',
      'plugin_id' => 'some_block_config',
    ];
    $helper = new PathChangedHelper(
      new RouteMatch('path.changed.bc', $route, [], $raw_parameters),
      new Request($query)
    );

    // Assert that oldPath() returns the internal path for path.changed.bc.     $this->assertEquals('old/path/test_block_type', $helper->oldPath());
    // Assert that newPath() returns the internal path for path.changed.     $this->assertEquals('new/path/test_block_type', $helper->newPath());
    // Assert that redirect() returns a RedirectResponse for the absolute URL of     // path.changed, and the query string comes from the Request object with the     // destination parameter removed.     $redirect = $helper->redirect();
    $this->assertInstanceOf(RedirectResponse::class, $redirect);
    $this->assertEquals(301, $redirect->getStatusCode());
    $base_path = Url::fromRoute('<front>', [], ['absolute' => TRUE])->toString();
    $this->assertEquals($base_path . 'new/path/test_block_type?plugin_id=some_block_config', $redirect->getTargetUrl());
  }

}

  public function blockContentTypeRedirect(RouteMatchInterface $route_match, Request $request): RedirectResponse {
    @trigger_error('The path /admin/structure/block/block-content/types is deprecated in drupal:10.1.0 and is removed from drupal:11.0.0. Use /admin/structure/block-content. See https://www.drupal.org/node/3320855.', E_USER_DEPRECATED);
    $helper = new PathChangedHelper($route_match, $request);
    $params = [
      '%old_path' => $helper->oldPath(),
      '%new_path' => $helper->newPath(),
      '%change_record' => 'https://www.drupal.org/node/3320855',
    ];
    $warning_message = $this->t('You have been redirected from %old_path. Update links, shortcuts, and bookmarks to use %new_path.', $params);
    $this->messenger()->addWarning($warning_message);
    $this->getLogger('block_content')->warning('A user was redirected from %old_path. This redirect will be removed in a future version of Drupal. Update links, shortcuts, and bookmarks to use %new_path. See %change_record for more information.', $params);

    return $helper->redirect();
  }

  /** * Provides a redirect to the content block library. * * @param \Drupal\Core\Routing\RouteMatchInterface $route_match * A route match object, used for the route name and the parameters. * @param \Symfony\Component\HttpFoundation\Request $request * The current request object. * * @return \Symfony\Component\HttpFoundation\RedirectResponse * * @deprecated in drupal:10.1.0 and is removed from drupal:11.0.0. Use * /admin/content/block directly instead of * /admin/structure/block/block-content. * * @see https://www.drupal.org/node/3320855 */