Remove DCGs that have thrown an exception during term expansion #2681
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Some DCG constructs aren't supported and can't be expanded, here we remove offending DCG rule and don't compile it at all – in a similar fashion to what we do when incorrect goal was found – whole predicate isn't getting compiled. Fixes mthom#2675
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Thank you a lot for taking a look at this issue! Regarding the approach: In which module is |
src/lib/dcgs.pl
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| @@ -216,7 +219,7 @@ | |||
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| user:term_expansion(Term0, Term) :- | |||
| nonvar(Term0), | |||
| dcg_rule(Term0, Term). | |||
| catch(dcg_rule(Term0, Term), E, (Term = null, format(" ~q~n", [E]))). | |||
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A blind catchall just leads to further problems. So restrict it to those terms that make sense here. Further, note that many implementations permit lists of clauses including [].
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Yes, I would also like to use an empty list, but currently Scryer just compiles a clause []/0, which isn't what I want to achieve here. Maybe that is a more deep problem to be solved instead.
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One can always define the fact [] with the rule [] :- true.
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Oh... I forgot to push a commit
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Additionally I do think that this has to be fixed in Prolog, because Rust code that generates this warning is applied universally to every compiled clause, so I will need to add an ugly special treatment for |
Some DCG constructs aren't supported and can't be expanded, here we remove offending DCG rule and don't compile it at all – in a similar fashion to what we do when incorrect goal was found – whole predicate isn't getting compiled.
Fixes #2675
I know that request has low priority, but it is so much simpler than loder.pl refactoring, so I just couldn't help myself and fixed it right away.