#8135: Panic when printing out kind incompatibility error ------------------------------------+------------------------------------- Reporter: Saulzar | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- I wrote a little utility function against the new pipes 4.0 repository but neglected to put the brackets around lift (f x) like so: mapM :: (Monad m) => (a -> m b) -> Pipe a b m r mapM f = for cat $ \x -> do r <- lift f x yield r Which resulted in this error/panic. src/Utils/Pipes.hs:13:8: Couldn't match kind `* -> *' with `*' Expected type: a -> Proxy () a () b m b Actual type: a -> Proxy () a () b m b Kind incompatibility when matching types: a :: * -> * a :: * The function `lift'ghc: panic! (the 'impossible' happened) (GHC version 7.6.2 for x86_64-unknown-linux): kindFunResult ghc-prim:GHC.Prim.*{(w) tc 34d} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8135 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler