#9106: GHC Panic related to functional dependencies - kindFunResult ---------------------------------------+--------------------------- Reporter: yuriy | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Windows | Architecture: x86 Type of failure: Compile-time crash | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: ---------------------------------------+--------------------------- Comment (by darchon): Also annotating the `Z` instance with an explicit kind, `(f :: *)`, makes the `GHC.TypeLits` version work: {{{ {-# LANGUAGE MultiParamTypeClasses, DataKinds, FunctionalDependencies, TypeOperators, KindSignatures, PolyKinds, FlexibleInstances, FlexibleContexts, UndecidableInstances, ScopedTypeVariables #-} module FunctorN where import GHC.TypeLits data Proxy (a :: k) = Proxy class FunctorN n f a fa | n f a -> fa where fmapn :: Proxy n -> Proxy f -> (a -> a) -> fa -> fa instance FunctorN 0 (f :: *) a a where fmapn _ _ a = a instance (Functor f, FunctorN (n - 1) f a fa) => FunctorN n f a (f fa) where fmapn _ pf f = fmap (fmapn (Proxy :: Proxy (n-1)) pf f) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9106#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler