#16347: GHC HEAD regression: piResultTys1 -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: Component: Compiler | Version: 8.7 (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: -------------------------------------+------------------------------------- The following program typechecks on GHC 8.0.2 through 8.6.3, but panics on HEAD: {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeInType #-} module Bug where import Data.Kind import Data.Proxy data T f :: f Type -> Type where MkT :: T f a }}} {{{ $ ~/Software/ghc4/inplace/bin/ghc-stage2 Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.7.20190219 for x86_64-unknown-linux): piResultTys1 k_a10k[tau:1] [*] Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1159:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:1063:5 in ghc:Type }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16347 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler