In [Cache \(Symfony 3\.4 Docs\)](https://symfony.com/doc/3.4/cache.html#configuring-cache-with-frameworkbundle), `cache.adapter.array` is listed as a valid service, but it doesn't actually work, because it's not exposed as a service. https://github.com/symfony/framework-bundle/blob/v3.4.30/Resources/config/cache.xml https://github.com/symfony/framework-bundle/blob/v4.3.3/Resources/config/cache.xml#L136-L143 Isn't this service introduced from Symfony 4.1? I can't find service definition in Symfony 4.0 and 3.4.