I can't reproduce the original problem with -rc2 either This is very bizarre: I just updated to the latest build in fedora (which still identifies itself with the same version) and couldn't reproduce the crash either. But the example by aavogt above also crashes for me. And
#11681: ghc panic with TypeError -------------------------------------+------------------------------------- Reporter: inaki | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler (Type | Version: 8.0.1-rc2 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by inaki): Replying to [comment:5 aavogt]: playing around with my original example, the following **does** crash: {{{#!hs {-# LANGUAGE DataKinds, FlexibleContexts, TypeOperators, FlexibleInstances #-} import GHC.TypeLits class C t where instance (TypeError (Text "A" :<>: {- Text -} "B")) => C t where main :: IO () main = return () }}} Notice the absence of the `UndecidableInstances` extension, the content is otherwise identical. It is not impossible I made a mistake when copying the original example for the crash, apologies if this was the case. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11681#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler