GADT + Newtype deriving = Erroneous errors

[Tomasz Zielonka]

On Mon, Mar 26, 2007 at 09:18:34PM -0700, Stefan O'Rear wrote:
> stefan at stefans:/tmp$ cat A.lhs
> > {-# OPTIONS_GHC -fglasgow-exts #-}
> >
> > data IsIntT x where IsIntT :: IsIntT Int
> >
> > class IsIntC a where isInt :: IsIntT a
> > instance IsIntC Int where isInt = IsIntT
> >
> > newtype Foo = Foo Int deriving(IsIntC)

I think newtype deriving should be rejected in this case. Maybe this is
the real problem here?

Best regards
Tomek