What's wrong with symfony?

Question

symfony

Started throwing this error (even if it's a newly created project):
An exception has been thrown during the rendering of a template ("[Semantical Error] The annotation "@Route" in method AppBundle\Controller\DefaultController::indexAction() was never imported. Did you maybe forget to add a "use" statement for this annotation? site_symfony/my_project_name/app/config/routing.yml"). Make sure annotations are installed and enabled.").
 
This is also written, but it still gives an error
use Symfony\Component\Routing\Annotation\Route;

symfony version 3.4