I'm pretty sure raiseIO#, catch#, maskAsyncExceptions#, and so on can have open-kinded results. For example, we currently have catch# :: (State# RealWorld -> (# State# RealWorld, a #) ) -> (b -> State# RealWorld -> (# State# RealWorld, a #) ) -> State# RealWorld -> (# State# RealWorld, a #) but I think we *should* be able to have catch# :: (State# RealWorld -> (# State# RealWorld, o #) ) -> (b -> State# RealWorld -> (# State# RealWorld, o #) ) -> State# RealWorld -> (# State# RealWorld, o #) This should allow us to avoid boxing things just to be able to get them out of a `catch#` or `maskAsyncExceptions#` block. But when I tried just changing the types in primops.txt.pp, I got a type mismatch error that seems to suggest some sort of GHC build staging issue. How can I work around this? See https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4192/diffs for my attempt.