[PasswordHasher] Fix incompatibility with 6.0

Author: wouterj

Hasher/UserPasswordHasher.php

@@ -48,7 +48,7 @@ public function hashPassword($user, string $plainPassword): string
         if ($user instanceof LegacyPasswordAuthenticatedUserInterface) {
             $salt = $user->getSalt();
         } elseif ($user instanceof UserInterface) {
-            $salt = $user->getSalt();
+            $salt = method_exists($user, 'getSalt') ? $user->getSalt() : null;
 
             if ($salt) {
                 trigger_deprecation('symfony/password-hasher', '5.3', 'Returning a string from "getSalt()" without implementing the "%s" interface is deprecated, the "%s" class should implement it.', LegacyPasswordAuthenticatedUserInterface::class, get_debug_type($user));

Tests/Fixtures/TestLegacyPasswordAuthenticatedUser.php

@@ -30,23 +30,23 @@ public function getPassword(): ?string
         return $this->password;
     }
 
-    public function getRoles()
+    public function getRoles(): array
     {
         return $this->roles;
     }
 
-    public function eraseCredentials()
+    public function eraseCredentials(): void
     {
         // Do nothing
         return;
     }
 
-    public function getUsername()
+    public function getUsername(): string
     {
         return $this->username;
     }
 
-    public function getUserIdentifier()
+    public function getUserIdentifier(): string
     {
         return $this->username;
     }