#11275: :kind! doesn't reduce type families with poly-kinded return kinds -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Originally discovered [https://mail.haskell.org/pipermail/ghc- devs/2015-December/010831.html here], here is a simplified example: {{{ $ ghci GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help λ> :set -XPolyKinds -XTypeFamilies λ> type family Hm :: k where Hm = Int λ> :kind! Hm Hm :: k = Hm }}} Giving `Hm` a monomorphic return kind of `*` makes it work with `:kind!`: {{{ $ ghci GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help λ> :set -XTypeFamilies λ> type family Hm :: * where Hm = Int λ> :kind! Hm Hm :: * = Int }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11275 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler