interactive co-recursion

I've no idea if the following is supposed to work, but the message
tells me to report it, so here it is.  Happens for all attempts to
define co-recursive functions, this is just the simplest example.

  Prelude> let { f = g ; g = f}
  ghc-6.0: panic! (the `impossible' happened, GHC version 6.0):
        getLinkDeps No iface for [<pkg>]DataziTuple
 
  Please report it as a compiler bug to glasgow-haskell-bugs@xxxxxxxxxxx,
  or http://sourceforge.net/projects/ghc/.

-kzm
-- 
If I haven't seen further, it is by standing in the footprints of giants