[Haskell] Should the following program be accepted by ghc?

[Don Stewart]

stefanor:
> On Wed, Jan 16, 2008 at 01:02:43PM +0800, Martin Sulzmann wrote:
> > Bruno Oliveira writes:
> >  > I have been playing with ghc6.8.1 and type families and the following 
> >  > program is accepted without any type-checking error:
> >  > 
> >  > > data a :=: b where
> >  > >    Eq :: a :=: a
> ...
> >  > Ofcourse, that before ghc6.8, we add no type-level functions so maybe it 
> >  > was ok to consider the program above. 
> ...
> >  > > type family K a
> 
> Type families are unsupported, and their intersection with GADTs are
> unimplemented.  Don't expect any program which uses both to do anything
> sane until 6.10.

That being said, bug reports against the head version of GHC *are*
welcome. But they're not an official feature of ghc 6.8, as Stefan
hinted.

-- Don