Merge branch '6.3' into 6.4

* 6.3:
  [TwigBridge] Change return type of Symfony\Bridge\Twig\AppVariable::getSession()
  [mailer] reset $code variable each iteration for prevent wrong codes to be used
  bug [mailer] fix EsmtpTransport variable $code definition
  UrlHelper: minor code style fix
  [Serializer] Looking for DiscriminatorMap on interfaces when the current object also extends from a class
  [DoctrineBridge][Security] Rename loadUserByUsername tests to loadUserByIdentifier

Author: fabpot

AppVariable.php

@@ -13,7 +13,7 @@
 
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\RequestStack;
-use Symfony\Component\HttpFoundation\Session\Session;
+use Symfony\Component\HttpFoundation\Session\SessionInterface;
 use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
 use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
 use Symfony\Component\Security\Core\User\UserInterface;
@@ -112,7 +112,7 @@ public function getRequest(): ?Request
     /**
      * Returns the current session.
      */
-    public function getSession(): ?Session
+    public function getSession(): ?SessionInterface
     {
         if (!isset($this->requestStack)) {
             throw new \RuntimeException('The "app.session" variable is not available.');
@@ -171,6 +171,12 @@ public function getFlashes(string|array $types = null): array
             return [];
         }
 
+        // In 7.0 (when symfony/http-foundation: 6.4 is required) this can be updated to
+        // check if the session is an instance of FlashBagAwareSessionInterface
+        if (!method_exists($session, 'getFlashBag')) {
+            return [];
+        }
+
         if (null === $types || '' === $types || [] === $types) {
             return $session->getFlashBag()->all();
         }