[ ghc-Bugs-1175398 ] buggy class causes unifyTauTyLists mismatch

[SourceForge.net]

Bugs item #1175398, was opened at 2005-04-02 07:18
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=108032&aid=1175398&group_id=8032

Category: Compiler
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: buggy class causes unifyTauTyLists mismatch

Initial Comment:
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 at 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".

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=108032&aid=1175398&group_id=8032