Merge branch '6.4' into 7.3

* 6.4:
  [VarExporter] Fix serializing classes with __serialize() returning unprefixed private properties
  Remove direct access to internal properties cross-components

Author: nicolas-grekas

Tests/Validator/Constraints/UserPasswordTest.php

@@ -42,20 +42,20 @@ public static function provideServiceValidatedConstraints(): iterable
         $metadata = new ClassMetadata(UserPasswordDummy::class);
         self::assertTrue((new AttributeLoader())->loadClassMetadata($metadata));
 
-        yield 'attribute' => [$metadata->properties['b']->constraints[0]];
+        yield 'attribute' => [$metadata->getPropertyMetadata('b')[0]->getConstraints()[0]];
     }
 
     public function testAttributes()
     {
         $metadata = new ClassMetadata(UserPasswordDummy::class);
         self::assertTrue((new AttributeLoader())->loadClassMetadata($metadata));
 
-        [$bConstraint] = $metadata->properties['b']->getConstraints();
+        [$bConstraint] = $metadata->getPropertyMetadata('b')[0]->getConstraints();
         self::assertSame('myMessage', $bConstraint->message);
         self::assertSame(['Default', 'UserPasswordDummy'], $bConstraint->groups);
         self::assertNull($bConstraint->payload);
 
-        [$cConstraint] = $metadata->properties['c']->getConstraints();
+        [$cConstraint] = $metadata->getPropertyMetadata('c')[0]->getConstraints();
         self::assertSame(['my_group'], $cConstraint->groups);
         self::assertSame('some attached data', $cConstraint->payload);
     }