[GHC] #9106: GHC Panic related to functional dependencies - kindFunResult
GHC
ghc-devs at haskell.org
Tue May 13 21:44:00 UTC 2014
#9106: GHC Panic related to functional dependencies - kindFunResult
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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:
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Comment (by yuriy):
The same code without {{{GHC.TypeLits}}} works:
{{{
{-# LANGUAGE
MultiParamTypeClasses, DataKinds, FunctionalDependencies, TypeOperators,
KindSignatures, PolyKinds, FlexibleInstances, FlexibleContexts,
UndecidableInstances,
ScopedTypeVariables #-}
data Proxy (a :: k) = Proxy
data Nat = Z | P Nat
class FunctorN n f a fa | n f a -> fa where
fmapn :: Proxy n -> Proxy f -> (a -> a) -> fa -> fa
instance FunctorN Z f a a where
fmapn _ _ a = a
instance (Functor f, FunctorN n f a fa) => FunctorN (P n) f a (f fa) where
fmapn _ pf f = fmap (fmapn (Proxy :: Proxy n) pf f)
}}}
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9106#comment:1>
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