As of Symfony 2.8, implementing thegetName() method of theFormTypeInterface() is deprecated. Instead, form types should be referenced by their FQCN (which is quite easy as PHP supports theclass constant since 5.5). Additionally, you should now also not use thealias attribute anymore when tagging your services as a form type using theform.type tag.

More detailed information and examples can be found in the code PR (seesymfony/symfony#15079) which has just been merged.