Hello, I there is a problem with form.type_extension because the attribute "alias" is ignored
https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/FrameworkBundle/Resources/config/form.xml#L187

The error dumped is:

[InvalidArgumentException]
Tagged form type extension must have the extended type configured using the extended_type/extended-type attribute, none was configured for the "form.type_extension.upload.validator" service. 

Since I could not find any related issue I dont really know if this is a known problem. Maybe I did some bad but. To replicate this problem:

symfony new my_project
Change minimun stability to dev in composer.json
composer update

Maybe I'm doing it wrong for getting de development version.

Thank you