[m-dev.] for review: fix existential types bug

[Simon Taylor]

> 
> On 25-Oct-1999, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> > 
> > compiler/polymorphism.m:
> > 	Add the type-info variables added for the existential
> > 	type variables of a constructor to the non-locals of
> > 	the construction.
> 
> Hmm... why doesn't the call to implicitly_quantify_goal
> in polymorphism__fixup_quantification fix that?
> (polymorphism__fixup_quantification is called from
> polymorphism__process_clause.)

implicitly_quantify_goal is only called from
polymorphism__fixup_quantification if the predicate being
processed has type variables in the argument types.
This does not check whether called predicates, functions
or constructors have type variables in their argument types.

> > +		goal_info_get_nonlocals(GoalInfo0, NonLocals0),
> > +		set__insert_list(NonLocals0, ExtraVars, NonLocals),
> > +		goal_info_set_nonlocals(GoalInfo0, NonLocals, GoalInfo),
> >  		Unify = unify(X0, functor(ConsId, ArgVars), Mode0,
> > -				Unification0, UnifyContext) - GoalInfo0,
> > +				Unification0, UnifyContext) - GoalInfo,
> >  		list__append(ExtraGoals, [Unify], GoalList),
> >  		conj_list_to_goal(GoalList, GoalInfo0, Goal)
> 
> Shouldn't that last occurrence of `GoalInfo0' be `GoalInfo'?

No, because the extra type-infos are local to that conjunction.

Simon.
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