GHC HEAD panic (dischargeFmv)
The following program panics on GHC HEAD:
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilyDependencies #-}
{-# LANGUAGE TypeInType #-}
{-# LANGUAGE TypeOperators #-}
module Bug where
import Data.Kind
import Data.Proxy
data family Sing (a :: k)
data SomeSing :: Type -> Type where
SomeSing :: Sing (a :: k) -> SomeSing k
class SingKind k where
type Demote k = (r :: Type) | r -> k
fromSing :: Sing (a :: k) -> Demote k
toSing :: Demote k -> SomeSing k
withSomeSing :: forall k r
. SingKind k
=> Demote k
-> (forall (a :: k). Sing a -> r)
-> r
withSomeSing x f =
case toSing x of
SomeSing x' -> f x'
newtype instance Sing (f :: k1 ~> k2) =
SLambda { applySing :: forall t. Sing t -> Sing (f @@ t) }
instance (SingKind k1, SingKind k2) => SingKind (k1 ~> k2) where
type Demote (k1 ~> k2) = Demote k1 -> Demote k2
fromSing sFun x = withSomeSing x (fromSing . applySing sFun)
toSing = undefined
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 = Apply f x
infixl 9 @@
dcomp :: forall (a :: Type)
(b :: a ~> Type)
(c :: forall (x :: a). Proxy x ~> b @@ x ~> Type)
(f :: forall (x :: a) (y :: b @@ x). Proxy x ~> Proxy y ~> c @@ ('Proxy :: Proxy x) @@ y)
(g :: forall (x :: a). Proxy x ~> b @@ x)
(x :: a).
SingKind (c @@ ('Proxy :: Proxy x) @@ (g @@ ('Proxy :: Proxy x)))
=> (forall (xx :: a) (yy :: b @@ xx). Sing (f @@ ('Proxy :: Proxy xx) @@ ('Proxy :: Proxy yy)))
-> Sing g
-> Sing a
-> Demote (c @@ ('Proxy :: Proxy x) @@ (g @@ ('Proxy :: Proxy x)))
dcomp _sf _ _ = undefined$ /opt/ghc/head/bin/ghc Bug2.hs
[1 of 1] Compiling Bug ( Bug2.hs, Bug2.o )
ghc: panic! (the 'impossible' happened)
(GHC version 8.5.20180501 for x86_64-unknown-linux):
dischargeFmv
[D] _ {0}:: (Apply
(f_a1ih[sk:2] xx_a1iA[tau:3] yy_a1iB[tau:3] |> Sym ((TyFun
<Proxy xx_a1iA[tau:3]>_N
((TyFun
(Proxy
(Sym {co_a1jm})
(Coh <yy_a1iB[tau:3]>_N
{co_a1jm}))_N
(Sym {co_a1jB} ; (Apply
(Sym {co_a1jm})
<*>_N
(Coh ((Coh <s_a1jn[fmv:0]>_N
((TyFun
(Sym {co_a1jm})
<*>_N)_N
->_N <*>_N) ; Sym {co_a1jA}) ; (Apply
<Proxy
xx_a1iA[tau:3]>_N
((TyFun
(Sym {co_a1jm})
<*>_N)_N
->_N <*>_N)
(Coh <c_a1ig[sk:2] xx_a1iA[tau:3]>_N
(Sym ((TyFun
<Proxy
xx_a1iA[tau:3]>_N
((TyFun
(Sym {co_a1jm})
<*>_N)_N
->_N <*>_N))_N
->_N <*>_N)))
<'Proxy>_N)_N)
(Sym ((TyFun
(Sym {co_a1jm})
<*>_N)_N
->_N <*>_N)))
(Coh <yy_a1iB[tau:3]>_N
{co_a1jm}))_N))_N
->_N <*>_N))_N
->_N <*>_N))
'Proxy :: (Proxy (yy_a1iB[tau:3] |> {co_a1jm}) ~> s_a1jp[fmv:0]))
~# (s_a1jQ[fmv:0] :: (Proxy (yy_a1iB[tau:3] |> {co_a1jm})
~> s_a1jp[fmv:0]))
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/utils/Outputable.hs:1162:37 in ghc:Outputable
pprPanic, called at compiler/typecheck/TcSMonad.hs:3047:25 in ghc:TcSMonadOn GHC 8.4.2, it simply throws an error:
$ /opt/ghc/8.4.2/bin/ghci Bug2.hs
GHCi, version 8.4.2: http://www.haskell.org/ghc/ :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug ( Bug2.hs, interpreted )
Bug2.hs:53:71: error:
• Expected kind ‘Apply b xx’, but ‘y’ has kind ‘b @@ x’
• In the first argument of ‘Proxy’, namely ‘y’
In the first argument of ‘(~>)’, namely ‘Proxy y’
In the second argument of ‘(~>)’, namely
‘Proxy y ~> c @@ ( 'Proxy :: Proxy x) @@ y’
|
53 | (f :: forall (x :: a) (y :: b @@ x). Proxy x ~> Proxy y ~> c @@ ('Proxy :: Proxy x) @@ y)
| ^Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.5 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler (Type checker) |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |