**Symfony version(s) affected**: master branch **Description** When trying to create *any* form type, a strange container require failure occurs: <img width="1056" alt="screen shot 2018-08-09 at 12 16 13 pm" src="https://user-images.githubusercontent.com/121003/43911749-39ea63ce-9bce-11e8-916e-5f77366834e3.png"> **How to reproduce** I have a small app that reproduces it here: https://github.com/weaverryan/bug-symfony-container-reproducer Just start the built-in web server and go to `/` to see the error. To create the reproducer app, I: 1) Created a symfony/skeleton project from dev-master 2) Installed symfony/form (dev-master) 3) Try to create a form in a controller: https://github.com/weaverryan/bug-symfony-container-reproducer/blob/master/src/Controller/ContainerTestController.php#L12 If you have any questions, please let me know! I don't think I'm doing anything funny to cause it, but you never can be sure ;). Cheers!