`meta_predicate` doesn't accept predicate indicator sequence nor list

[hurufu]

In order to maintain compatibility with SICStus which was discovered while trying to run original reif.pl implementation, it looks like meta_predicate directive should be extended to accept predicate indicator sequence and list (similar to #1586).

I've tried to do it myself, but code for registering meta-predicate records differs from other directives quite significantly that I couldn't just copy/adapt code from others.

[hurufu]

Relevant task: #1302, and commit a4d15bf.

[Skgland]

op/3 are handled in the toplevel https://github.com/mthom/scryer-prolog/blob/master/src/toplevel.pl#L171-L179 turning the declaration using a list into individual declarations.
Wouldn't that work analog for meta_predicate ? I.e.

user:term_expansion((:- meta_predicate(Metas)), MetaResults) :- 
    ground(Metas), 
    Metas= [Meta| OtherMetas],
    expand_meta_list([Meta| OtherMetas], MetaResults).

expand_meta_list([], _, _, []).
expand_meta_list([Meta| OtherMetas], [(:- meta_predicate(Meta)) | OtherResults]) :-
    expand_meta_list(OtherMetas, OtherResults).

[hurufu]

Ineteresting idea, I initially thought to add two more instructions to dispatch.rs: CallAddMetaPredicateRecord, ExecuteAddMetaPredicateRecord and then handle it in loader.rs by calling loader.add_meta_predicate_record(...). But I never finished that code.

UPDT: Also I'm not sure, but it looks like meta_predicate handling is done during preprocessing stage, ie before goal expansion.