Unexpected behaviour of lib_machine::Machine::run_query

[zshehov]

There seems to be a bug in lib_machine::Machine::run_query that results in wrong resolutions. To reproduce:

      let mut machine = Machine::new_lib();

      machine.load_module_string(
          "facts",
          String::from(
              r#"
          male(stephen).
          parent(albert,edward).
          father(F,C):-parent(F,C),male(F).
      "#,
          ),
      );

      let query = String::from(r#"father(F,C)."#);
      let output = machine.run_query(query);

Expected output: QueryResolution::False
Actual output: Matches([QueryMatch { bindings: {"C": String("edward"), "F": String("albert")} }])

Note: running the same program in scryer-prolog:

$ scryer-prolog
?- [user].
male(stephen).
parent(albert,edward).
father(F,C):-parent(F,C),male(F).

?- father(F,C).
   false.

[triska]

@lucksus, could you please help with this issue? Is this maybe even addressed with the recently merged #2309?

[mthom]

This appears already to be solved! I added a test case for it to lib_machine.rs in f2d3779.

[zshehov]

Confirming this is working as expected in v0.9.4 and closing the issue. Thanks!