GHC Panic on over-saturated associated type family
If we over-saturate a type family
{-# Language TypeFamilies, ScopedTypeVariables, PolyKinds, DataKinds #-}
import Data.Kind
class R (c :: k -> Constraint) where
type R_ (c :: k -> Constraint) :: k -> Type
instance R Eq where
type R_ Eq a = a -> a -> Bool
we get
$ ghci -ignore-dot-ghci test.hs
GHCi, version 8.3.20170605: http://www.haskell.org/ghc/ :? for help
[1 of 1] Compiling Main ( test.hs, interpreted )
ghc: panic! (the 'impossible' happened)
(GHC version 8.3.20170605 for x86_64-unknown-linux):
repSplitAppTys
a_a2qu[sk:1]
a_a2qu[sk:1] -> Bool
[]
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/types/Type.hs:809:9 in ghc:Type
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
>
Trac metadata
Trac field | Value |
---|---|
Version | 8.2.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |