[m-dev.] for review: change typecheck.m to handle type class inference

[David Glen JEFFERY]

On 30-Mar-1998, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> Hi,
> 
> DJ, can you please review this one?
> 
> Estimated hours taken: 2
> 
> compiler/typecheck.m:
> 	Get type inference working for type classes.
> 
> tests/hard_coded/typeclasses/Mmakefile:
> tests/hard_coded/typeclasses/inference_test.m:
> tests/hard_coded/typeclasses/inference_test.exp:
> 	Add a simple test case for type class inference.
> 
> Index: compiler/typecheck.m
> ===================================================================
> +				% if the argument types and the type
> +				% constraints are identical up to renaming,
> +				% then nothing has changed
> +				% (the call to same_length is just an
> +				% optimization -- catch the easy cases first)
> +				list__same_length(OldTypeConstraints,
> +					InferredTypeConstraints),
> +				same_structure(OldTypeConstraints,
> +					InferredTypeConstraints,
> +					ConstrainedTypes0, ConstrainedTypes),
> +				list__append(ConstrainedTypes0, ArgTypes0,
> +					TypesList0),
> +				list__append(ConstrainedTypes, ArgTypes,
> +					TypesList),
> +				identical_up_to_renaming(TypesList0, TypesList)

Could you avoid these two appends by just calling identical_up_to_renaming
twice?

> +:- pred rename_class_constraint(map(tvar, tvar), class_constraint,
> +				class_constraint).
> +:- mode rename_class_constraint(in, in, out) is det.
> +
> +% apply a type variable renaming to a class constraint
> +
> +rename_class_constraint(TSubst, constraint(ClassName, ArgTypes0),
> +			constraint(ClassName, ArgTypes)) :-
> +	term__apply_variable_renaming_to_list(ArgTypes0, TSubst, ArgTypes).
> +
> +:- pred rename_constraint_proof(map(tvar, tvar), constraint_proof,
> +				constraint_proof).
> +:- mode rename_constraint_proof(in, in, out) is det.
> +
> +% apply a type variable renaming to a class constraint proof
> +
> +rename_constraint_proof(_TSubst, apply_instance(Instance, Num),
> +				apply_instance(Instance, Num)).
> +rename_constraint_proof(TSubst, superclass(ClassConstraint0),
> +			superclass(ClassConstraint)) :-
> +	rename_class_constraint(TSubst, ClassConstraint0, ClassConstraint).
> +

These should go in type_util.m, next to apply_subst_to_constraint and its
cousins.

Apart from that, this diff looks fine. Thanks.


love and cuddles,
dgj
-- 
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