#15079: GHC HEAD regression: cannot instantiate higher-rank kind -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.6.1 Component: Compiler (Type | Version: 8.5 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I too find it rather bizarre that the visibilities of each type variable binder have to line up when instantiating a higher-rank kind, since that isn't a requirement for higher-rank types: {{{#!hs {-# LANGUAGE RankNTypes #-} module Bug where id' x = x f :: (forall a. a -> a) -> b -> c -> (b, c) f g b c = (g b, g c) h :: b -> c -> (b, c) h = f id' }}} `h` typechecks, despite the fact that the type of `id'` is `forall {p}. p -> p` (i.e., with an inferred variable), and `f` is supposed to take an argument of type `forall a. a -> a` (i.e., with a specified variable). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15079#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler