
#9305: GHC panic when deriving Functor on a Fixed type -----------------------------------+--------------------------------------- Reporter: andreyLevushkin | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: Compile-time crash Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | -----------------------------------+--------------------------------------- Building the following {{{ #!haskell {-# LANGUAGE DeriveFunctor#-} module Main where data Event a b = Event a deriving (Functor) newtype F f = F (f (F f)) data EventF a = EventF (F (Event a)) deriving (Functor) }}} results in {{{ Main.hs:7:48:ghc: panic! (the 'impossible' happened) (GHC version 7.8.2 for x86_64-unknown-linux): Prelude.(!!): index too large }}} I am not sure if the above code should actually compile but it probably shouldn't panic. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9305 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler