[m-rev.] for post-commit review: fix Mantis bug 529

[Peter Wang]

On Thu, 25 Feb 2021 11:24:12 +1100 "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> 
> 2021-02-25 11:17 GMT+11:00 "Peter Wang" <novalazy at gmail.com>:
> > Are you planning to do more work on the mode checker?
> 
> Yes, I am trying to make getopt work by specifying the modes
> of the predicates stored in data structures in the types, not the
> modes. The bug529 fix is not enough to make that possible,
> since there are a bunch more places where the modechecker
> needs to get higher order inst info out of types.

That's a good idea.

> > I'm implementing
> > my subtypes proposal and will be touching the type checker and mode
> > checker this week and next week or so.
> 
> Just tell me when you are about to start work on the modechecker part.
> I will then commit whatever I have that is commit ready, and  give you
> free rein until you are done.

I have started on the mode checker. It's roughly working, with a lot of
details still to work through, but so far the change is isolated.
modecheck_goal_generic_call needs to handle a new type of "cast" (coerce)
by calling a new predicate. There shouldn't be any real conflicts unless
you plan on large refactorings. (But go ahead and commit your changes if
they are ready.)

Peter