Hi all, The Applicative Monad changes will be landing in HEAD soon, hopefully within a few hours once ./validate finishes and I triple-check everything. Why am I sending this? To warn you that you need to update Happy to *at least* version 1.19.4 before you can build GHC again. This is because Happy emitted parsers that had instances of Monad, and thus Happy needed to be fixed to also emit Applicative instances. Please be sure to upgrade your workstations, buildbots, toasters, etc so you don't get caught by surprise. ./configure will fail you if your Happy is invalid. This message is brought to you by sleep deprivation and almost two days of hunting an infinite loop in my changeset, which was quite annoying to track down. I'm sure something will still go wrong during ./validate... -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/