Skip to content

ScopedTypeVariables and PolyKinds

The following code panics:

{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE PolyKinds                  #-}

module Bug2 where


data TypeRep = TypeRep

data Proxy t = Proxy

typeRep :: Proxy a -> TypeRep
typeRep Proxy = TypeRep

-- This one works fine:
typeOf :: forall a. a -> TypeRep
typeOf _ = typeRep (Proxy :: Proxy a)

-- But this one panics!
typeOf1 :: forall t a. t a -> TypeRep
typeOf1 _ = typeRep (Proxy :: Proxy t)

{-
panic! (the 'impossible' happened)
  (GHC version 7.5.20111216 for x86_64-unknown-linux):
        tyConKind ghc-prim:GHC.Prim.BOX{(w) tc 347}
-}

I believe the problem is an interaction between !ScopedTypeVariables and !PolyKinds.

Trac metadata
Trac field Value
Version 7.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC jpm@cs.uu.nl
Operating system
Architecture
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information