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

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