#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 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: Compile-time crash | Difficulty: Unknown Test Case: T9305 | Blocked By: Blocking: | Related Tickets: ---------------------------------------+---------------------------------- Changes (by nomeata): * testcase: => T9305 Comment: I get {{{ T9305.hs:8:48: No instance for (Functor Event) arising from the first field of ‘EventF’ (type ‘F (Event a)’) Possible fix: use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (Functor EventF) }}} when trying with GHC head. I’m not quite sure if its the best error message, but it looks better than what you report, hence adding it as a (non-broken) test case. If convenient, can you check if it still happens with 7.8.3? Might be an already fixed and merged bug. Otherwise we should identify the fix and merge it for 7.8.4. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9305#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler