#11681: ghc panic with TypeError -------------------------------------+------------------------------------- Reporter: inaki | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When playing around with `TypeError` I got a ghc panic with the following code: {{{#!hs {-# LANGUAGE DataKinds, FlexibleContexts, TypeOperators, FlexibleInstances, UndecidableInstances #-} import GHC.TypeLits class C t where instance (TypeError (Text "A" :<>: {- Text -} "B")) => C t where main :: IO () main = return () }}} Compiling this results in {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.0.0.20160204 for x86_64-unknown-linux): fvProv falls into a hole {a1bh} }}} Commenting "in" the second `Text` removes the panic. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11681 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler