Simple example crashes GHC

This file:

class Collects ce where
  type Elem ce
  empty  :: ce
  insert :: Elem ce -> ce -> ce
  member :: Elem ce -> ce -> Bool
  toList :: ce -> [Elem ce]

and call GHC as: ghci -fglasgow-exts Abc gives:

GHCi, version 6.9.20070927: http://www.haskell.org/ghc/  :? for help
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( Abc.hs, interpreted )
ghc-6.9.20070927: panic! (the 'impossible' happened)
  (GHC version 6.9.20070927 for i386-unknown-linux):
        check_tau_type main:Main.Elem{tc rlp} ce{tv alz} [tv]

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Trac metadata

Trac field	Value
Version	6.9
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	iampure@gmail.com
Operating system	Unknown
Architecture	Unknown