#13202: Levity polymorphism panic in GHCi -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- With current `master`, {{{ $ ghci GHCi, version 8.1.20170126: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/ben/.ghci λ> import GHC.Exts λ> :set -XTypeApplications -XMagicHash -XTypeInType λ> data TypeRep (a :: k) = TypeRep λ> let typeRepKind = undefined :: TypeRep (a :: k) -> TypeRep k λ> let typeRep = undefined :: TypeRep (a :: k) λ> let x = typeRepKind (typeRep @(Maybe Int#)) ghc: panic! (the 'impossible' happened) (GHC version 8.1.20170126 for x86_64-unknown-linux): isUnliftedType forall (a :: TYPE q). a :: TYPE q Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1166:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1170:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:1869:10 in ghc:Type Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13202 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler