I have just tried the upgrade of an application to 2.6 and followed the upgrade document.

I noticed that there were major changes in the OptionResolver component with the depreciation
of the OptionResolverInterface. This was well documented in the OptionResolver documentation.

However it looks like there is no upgrade path for form classes extending the AbstractType since
the interface requires the OptionResolverInterface. I think we should offer an upgrade path to get
rid of the depreciation warnings. Will the AbstractType setDefaultOptions be changed in 3.0 or will
there be a new method?

@webmozart Or am I missing something?

Related symfony/symfony-docs#4159 #12156