[m-rev.] for review: type_spec and typeclass constraints

[David Overton]

On Tue, Aug 20, 2002 at 05:42:24AM +1000, Fergus Henderson wrote:
> On 20-Aug-2002, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> > 
> > But I see that David Overton has recently committed the following change,
> > which disallows cases like this:
> 
> Ouch!
> I guess we should add an example like that to the test suite.
> 
> David, was the part of the change which disallowed examples
> like that intentional?  If so, what's the rationale?

The rationale was simply that I didn't consider that such cases would be
useful or even make sense.  

My change actually relaxed the restrictions on what could appear in
constraint arguments, but I chose to be conservative and only relax the
restrictions as far as I thought at the time would be useful.

I don't see any problem with simply removing the check in prog_io_typeclass.
IIRC, I don't think there was any other part of my change that relied on the
assumption that there is at least one type variable in each constraint.


David
-- 
David Overton                  Uni of Melbourne     +61 3 8344 9159
dmo at cs.mu.oz.au                Monash Uni (Clayton) +61 3 9905 5779
http://www.cs.mu.oz.au/~dmo    Mobile Phone         +61 4 0337 4393
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