[m-rev.] for review: improve check for invalid invalid declarations

[Peter Ross]

On 9/28/07, Mark Brown <mark at csse.unimelb.edu.au> wrote:
> On 28-Sep-2007, Peter Ross <pro at missioncriticalit.com> wrote:
> >
> > For juliensf or pwa to review.
> >
> > ===================================================================
> >
> >
> > Estimated hours taken: 4
> > Branches: main
> >
> > Improve check for invalid instance declarations.
> >
> > compiler/check_typeclass.m:
> >       Check that each type in the instance declaration is a type with
> >       no arguments of a polymorphic type whose arguments are all distinct
> >       type variables.
>
> Hmm, there is already code to check this in parse_underived_instance_2
> in prog_io_typeclass.m.  I'm a bit puzzled why it apparently isn't working.
> Any clue?
>
because at that point it doesn't know anything about equivalence types.

> In any case, putting the check in the front end pass is a good idea, and
> is better than checking during parsing, IMHO.
>
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