Compiler panics on "phantom family"

Feeding the following innocent looking (well...) program into GHC causes the compiler to panic:

{-# OPTIONS_GHC -fglasgow-exts #-}

type family   KUnit a   :: *
type instance KUnit Int =  ()

unit :: KUnit Int
unit =  ()

The cry for help reads:

ghc-6.8.20071007: panic! (the 'impossible' happened)
  (GHC version 6.9.20070923 for powerpc-apple-darwin):
        check_tau_type main:Main.KUnit{tc rnu} base:GHC.Base.Int{(w) tc 3J}

Unsurprisingly, I've experienced the same behaviour with 6.9.20070923.

HTH,

Stefan Holdermans

Trac metadata

Trac field	Value
Version	6.8
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	abaars@iti.upv.es, stefan@cs.uu.nl
Operating system	Multiple
Architecture	Unknown