Symfony version(s) affected:
4.3 (Beta2 & RC1)

Description
Handling a request with a form that has an assigned Entity seems to wrongly trigger a ValidatorException.

How to reproduce
My apologies for the missing reproducer - I'm having issues creating it. since 4.3.0-RC1 is affected I thought sharing even without one could help.

        $entityManager = $this->getDoctrine()->getManager();
        $person = $entityManager->getRepository(Person::class)->findOneBy(['id' => $id]);

        $form = $this->createForm(PersonType::class, $person);
        $form->handleRequest($request);

triggers

ValidatorException: Property "xyz" does not exist in class "Proxies\__CG__\App\Entity\Person"

in PropertyMetadata.php#L39-L41

The stacktrace is here: https://gist.github.com/fabstei/ee254c7945ebc79fd3fed75cf4de82db

Possible Solution
None so far. After uncommenting PropertyMetadata.php#L39-L41 everything works as expected, but it's obviously not a solution.

Additional context

• Mac OS Mojave 10.14.5
• PHP 7.3.5