GHC Panic compiling type family with -XPolyKinds
I received the following error message:
ghc: panic! (the 'impossible' happened)
(GHC version 7.4.0.20111219 for x86_64-unknown-linux):
tyConKind ghc-prim:GHC.Prim.BOX{(w) tc 347}
I was compiling the following code:
{-# LANGUAGE TypeFamilies,
PolyKinds,
ScopedTypeVariables
#-}
convert :: a -> b
convert = undefined
type family Foo a
bar :: forall a b. b -> (Foo a)
bar f = (convert f :: (Foo a))
Interestingly, the output is different when changing the order in the forall (forall b a produces a different error). The same result happened on Linux/x86_64 and MacOS 10.7.2/x86_64-apple-darwin,
Trac metadata
Trac field | Value |
---|---|
Version | 7.4.1-rc1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |