#14175: Panic repSplitTyConApp_maybe -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.2 Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This definition panics! {{{#!hs {-# LANGUAGE TypeFamilies, TypeInType #-} module Whoops where import Data.Kind type family PComp (k :: j -> Type) (x :: k) :: () }}} {{{ ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.3.20170828 for x86_64-unknown-linux): repSplitTyConApp_maybe j_aon[sk:1] * * Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1138:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:1123:5 in ghc:Type }}} If I make it a type synonym instead, I get a proper error as expected. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14175 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler