#14880: GHC panic: updateRole -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.2.2 checker) | Resolution: | Keywords: Roles 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: | -------------------------------------+------------------------------------- Description changed by RyanGlScott: Old description:
The following program panics on GHC 8.0.2, 8.2.2, 8.4.1, and HEAD:
{{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} module Bug where
import Data.Kind import Data.Type.Equality ((:~:)(..))
type SameKind (a :: k) (b :: k) = (() :: Constraint)
data TyFun :: Type -> Type -> Type type a ~> b = TyFun a b -> Type infixr 0 ~>
type family Apply (f :: k1 ~> k2) (x :: k1) :: k2 type f @@ x = f `Apply` x infixl 9 @@
type family WhyCong (x :: Type) (y :: Type) (f :: x ~> y) (a :: x) (z :: x) (e :: a :~: z) :: Type where WhyCong _ _ f a z _ = f @@ a :~: f @@ z
data WhyCongSym1 (x :: Type) :: forall (a :: x) (y :: Type) (z :: x). Type ~> (x ~> y) ~> x ~> x ~> a :~: z ~> Type
data WhyCongSym0 :: forall (x :: Type) (a :: x) (y :: Type) (z :: x). Type ~> Type ~> (x ~> y) ~> x ~> x ~> a :~: z ~> Type where WhyCongSym0KindInference :: forall x arg. SameKind (Apply WhyCongSym0 arg) (WhyCongSym1 arg) => WhyCongSym0 x }}}
{{{ $ /opt/ghc/8.2.2/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-unknown-linux): updateRole WhyCongSym0 arg_aYV[sk:1] [aYU :-> 4, a22o :-> 0, a22p :-> 1, a22q :-> 2, a22r :-> 3] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/typecheck/TcTyDecls.hs:656:23 in ghc:TcTyDecls }}}
New description: The following program panics on GHC 8.0.2, 8.2.2, 8.4.1, and HEAD: {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} module Bug where import Data.Kind import Data.Type.Equality ((:~:)) type SameKind (a :: k) (b :: k) = (() :: Constraint) data TyFun :: Type -> Type -> Type type a ~> b = TyFun a b -> Type infixr 0 ~> type family Apply (f :: k1 ~> k2) (x :: k1) :: k2 data WhyCongSym1 (x :: Type) :: forall (a :: x) (y :: Type) (z :: x). Type ~> (x ~> y) ~> x ~> x ~> (a :~: z) ~> Type data WhyCongSym0 :: forall (x :: Type) (a :: x) (y :: Type) (z :: x). Type ~> Type ~> (x ~> y) ~> x ~> x ~> (a :~: z) ~> Type where WhyCongSym0KindInference :: forall x arg. SameKind (Apply WhyCongSym0 arg) (WhyCongSym1 arg) => WhyCongSym0 x }}} {{{ $ /opt/ghc/8.2.2/bin/ghci Bug.hs GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-unknown-linux): updateRole WhyCongSym0 arg_a1A6[sk:1] [a1A5 :-> 4, a2Cy :-> 0, a2Cz :-> 1, a2CA :-> 2, a2CB :-> 3] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/typecheck/TcTyDecls.hs:656:23 in ghc:TcTyDecls }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14880#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler