buggy class causes unifyTauTyLists mismatch

[nobody]

Obtained error in GHC:

Compiling Main             ( test.hs, interpreted )
ghc.exe: panic! (the `impossible' happened, GHC version
6.4):
        Unify.unifyTauTyLists: mismatched type lists!

Please report it as a compiler bug to
glasgow-haskell-bugs@haskell.org,
or http://sourceforge.net/projects/ghc/.

when :load called on buggy code:

class Foo f where
	baa :: f a -> f
instance Foo Maybe where
	baa z = z

On the other hand, Hugs identifies an error with an
"Illegal type in constructor application".

[simonpj]

Logged In: YES 
user_id=50165

Already fixed in the STABLE branch (and HEAD).  Thanks for 
the report though.