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

[David Glen JEFFERY]

On 15-Oct-1999, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> 
> Estimated hours taken: 12
> 
> Fix a bug with switches on existential types.  This bug meant that
> existential types with two or more functors did not work at all,
> due to internal compiler errors when compiling the unification and
> comparison predicates for those types.
> 
> compiler/type_util.m:
> 	Add new function cons_id_adjusted_arity, which computes the
> 	arity _including_ the extra typeinfo and typeclassinfo
> 	arguments inserted for existential data types.
> 
> compiler/type_util.m:
> compiler/polymorphism.m:
> 	Move the predicates constraint_list_get_tvars
> 	and constraint_get_tvars from polymorphism.m into
> 	type_util.m, for use in cons_id_adjusted_arity.
> 
> compiler/modes.m:
> compiler/unique_modes.m:
> 	When modechecking the functor test in switch statements,
> 	use cons_id_adjusted_arity to compute the arity of the inst.
> 
> compiler/instmap.m:
> 	In instmap__bind_var_to_functor (and the instmap_delta version),
> 	use cons_id_adjusted_arity to compute the arity of the inst.
> 
> compiler/goal_util.m:
> compiler/pd_info.m:
> compiler/pd_util.m:
> compiler/saved_vars.m:
> compiler/mode_util.m:
> compiler/deforest.m:
> compiler/follow_code.m:
> compiler/higher_order.m:
> compiler/simplify.m:
> 	Pass the type(s) down to recompute_instmap_delta and
> 	instmap__bind_var_to_functor, since cons_id_adjusted_arity
> 	needs to know the type.
> 
> compiler/hlds_pred.m:
> compiler/hlds_out.m:
> 	Add a `vartypes' typedef, defined by `:- type vartypes == map(prog_var, type)',
> 	and make use of it.  Rename the `vartypes' type in hlds_out as `maybe_vartypes'.
> 
> tests/hard_coded/Mmakefile:
> tests/hard_coded/existential_type_switch.m:
> tests/hard_coded/existential_type_switch.exp:
> 	Add a regression test.
> 
> tests/hard_coded/Mmakefile:
> 	Enable the existential_types_test.m test case,
> 	which should have been enabled previously.
> 	(The reason that it wasn't seems to be that I made
> 	a mistake when merging in the changes from the
> 	existential types branch.)



> +cons_id_adjusted_arity(ModuleInfo, Type, ConsId) = AdjustedArity :-
> +		% figure out the arity of this constructor,
> +		% _including_ any type-infos or typeclass-infos
> +		% inserted for existential data types.
> +	cons_id_arity(ConsId, ConsArity),
> +	(
> +		type_util__get_existq_cons_defn(ModuleInfo, Type, ConsId,
> +			ConsDefn)
> +	->
> +		ConsDefn = ctor_defn(_TVarSet, ExistQTVars, Constraints,
> +				_ArgTypes, _ResultType),
> +		list__length(Constraints, NumTypeClassInfos),
> +		constraint_list_get_tvars(Constraints, ConstrainedTVars),
> +		list__delete_elems(ExistQTVars, ConstrainedTVars,
> +				UnconstrainedExistQTVars),
> +		list__length(UnconstrainedExistQTVars, NumTypeInfos),
> +		AdjustedArity = ConsArity + NumTypeClassInfos + NumTypeInfos
> +	;
> +		AdjustedArity = ConsArity
> +	).

It is perhaps a little unfortunate that this code in typecheck.m has to know
how we add type infos and type class infos (ie. that we only add type infos
for unconstrained tvars), but I guess it is still the best place for this code.

Commit away (if you haven't already).


dgj
-- 
David Jeffery (dgj at cs.mu.oz.au) | If your thesis is utterly vacuous
PhD student,                    | Use first-order predicate calculus.
Dept. of Comp. Sci. & Soft. Eng.|     With sufficient formality
The University of Melbourne     |     The sheerist banality
Australia                       | Will be hailed by the critics: "Miraculous!"
                                |     -- Anon.
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