Crash with bogus FFI declaration

Ben Franksen finds this:

{-# LANGUAGE ForeignFunctionInterface, RankNTypes #-}
import Foreign
type X u = Ptr ()
foreign import ccall bla :: (forall u. X u) -> IO ()

I know of course that I must not use fancy types in foreign imports. I forgot for a moment and instead of an error message got:

ben@sarun> ghci Bug3
GHCi, version 6.10.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( Bug3.hs, interpreted )
ghc: panic! (the 'impossible' happened)
  (GHC version 6.10.1 for i386-unknown-linux):
        unboxArg:
    Bug3.hs:4:0-51 forall u{tv aht} [tv].
                   main:Main.X{tc rhp} u{tv aht} [tv]

Trac metadata

Trac field	Value
Version	6.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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