#13343: Levity polymorphism-related GHC panic: expectJust zonkTcTyVarToVar -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple LevityPolymorphism | Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Reproducible with GHC 8.0.2 and HEAD: {{{#!hs {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeInType #-} module Bug where import GHC.Exts type Bad = forall (v1 :: RuntimeRep) (a1 :: TYPE v). a1 }}} {{{ [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.1.20170223 for x86_64-unknown-linux): expectJust zonkTcTyVarToVar CallStack (from HasCallStack): error, called at compiler/utils/Maybes.hs:53:27 in ghc:Maybes expectJust, called at compiler/typecheck/TcType.hs:1576:21 in ghc:TcType }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13343 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler