#11334: GHC panic when calling typeOf on a promoted data constructor -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.1 (Type checker) | 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: -------------------------------------+------------------------------------- Here's what I did in GHCi to trigger the panic: {{{ $ inplace/bin/ghc-stage2 --interactive GHCi, version 8.1.20160101: http://www.haskell.org/ghc/ :? for help λ> :set -XDataKinds λ> :m Data.Typeable Data.Functor.Compose λ> typeOf (Proxy :: Proxy 'Compose) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.1.20160101 for x86_64-unknown-linux): piResultTy * TYPE 'Lifted * Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Enabling `-XPolyKinds` doesn't trigger the error, though; #10343 will be triggered instead: {{{ λ> :set -XPolyKinds λ> typeOf (Proxy :: Proxy 'Compose) <interactive>:5:1: error: • No instance for (Typeable a0) arising from a use of ‘typeOf’ • In the expression: typeOf (Proxy :: Proxy Compose) In an equation for ‘it’: it = typeOf (Proxy :: Proxy Compose) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11334 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler