In validator component, a metadata object can have a closure.

But when framework.validation.cache is used with validator.mapping.cache.doctrine.apc, the cache throws an exception because cache can't seraliaze a closure.

Uncaught PHP Exception Exception: "Serialization of 'Closure' is not allowed" at /path/vendor/doctrine/cache/lib/Doctrine/Common/Cache/ApcCache.php line 57 {"exception":"[object] (Exception(code: 0): Serialization of 'Closure' is not allowed