Add a warning when ApplicativeDo changes to monadic do
Could we please get a warning when a module that has ApplicativeDo enabled is using monadic do instead? I understand this would be an annoying warning for -Wall, but it could be useful to enable per-module so that you know when a do block is using a Monad instance instead of an Applicative instance. Currently, there doesn't seem to be any sort of user feedback to indicate this change and there are many subtle things that can trigger this behavior.