Find a Rector rule

 use Symfony\Component\Validator\Constraints as Assert;
 use Symfony\Component\Validator\Mapping\ClassMetadata;

 final class SomeClass
 {
+    #[Assert\NotBlank(message: 'City can\'t be blank.')]
     private $city;
-
-    public static function loadValidatorMetadata(ClassMetadata $metadata): void
-    {
-        $metadata->addPropertyConstraint('city', new Assert\NotBlank([
-            'message' => 'City can\'t be blank.',
-        ]));
-    }
 }

 use PHPUnit\Framework\TestCase;

 class SomeClass extends TestCase
 {
     public function run()
     {
         /** @var \Symfony\Component\HttpFoundation\Response $response */
         $response = $this->processResult();

-        $this->assertSame(200, $response->getStatusCode(), $response->getContent());
+        $this->assertSame(200, $response->getStatusCode(), (string) $response->getContent());
     }
 }

 use PHPUnit\Framework\TestCase;

 class SomeClass extends TestCase
 {
     public function run()
     {
         /** @var \Symfony\Component\HttpFoundation\Response $response */
         $response = $this->processResult();

-        $this->assertSame(200, $response->getStatusCode());
+        $this->assertSame(200, $response->getStatusCode(), $response->getContent());
     }
 }

 use Symfony\Component\HttpFoundation\Response;

 class SomeController
 {
     public function index()
     {
         $response = new Response();
-        $response->setStatusCode(200);
+        $response->setStatusCode(Response::HTTP_OK);

-        if ($response->getStatusCode() === 200) {
+        if ($response->getStatusCode() === Response::HTTP_OK) {
         }
     }
 }

-class SomeListener
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+class SomeEventSubscriber implements EventSubscriberInterface
 {
-     public function methodToBeCalled()
+     /**
+      * @return string[]
+      */
+     public static function getSubscribedEvents(): array
      {
+         return ['some_event' => 'methodToBeCalled'];
      }
-}

-// in config.yaml
-services:
-    SomeListener:
-        tags:
-            - { name: kernel.event_listener, event: 'some_event', method: 'methodToBeCalled' }
+     public function methodToBeCalled()
+     {
+     }
+}

 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Contracts\EventDispatcher\Event;

 final class SomeEventSubscriber implements EventSubscriberInterface
 {
     public static function getSubscribedEvents(): array
     {
         return ['some_event' => 'onEvent'];
     }

-    public function onEvent(Event $event): Event
+    public function onEvent(Event $event): void
     {
-        return $event->setSomething('value');
+        $event->setSomething('value');
     }
 }

 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Bundle\FrameworkBundle\Controller\Controller;

 final class SomeController extends Controller
 {
-    public function run(Request $request, int $id)
+    public function run(int $id)
     {
         echo $id;
     }
 }

 use Symfony\Bundle\FrameworkBundle\Controller\Controller;
 use Symfony\Component\Routing\Annotation\Route;

 final class SomeController extends Controller
 {
     /**
      * @Route(
      *     requirements={"number"="\d+"},
      * )
      */
-    public function detailAction($number)
+    public function detailAction(int $number)
     {
     }
 }

 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Routing\Annotation\Route;

 final class SomeController extends AbstractController
 {
     #[Route]
-    public function detail()
+    public function detail(): Response
     {
         return $this->render('some_template');
     }
 }