Wrong priority reported for the ('|')/2 operator

[pmoura]

In the rebis-dev branch (df779bb):

?- current_op(P, T, '|').
   P = 0, T = xfy
;  false.

Same issue in the master branch.

After some more digging, I believe this bug is responsible for #1569. The FCube port only defines this operator if the backend Prolog system doesn't define it itself. But a compliant definition is assumed (actual code simplified here):

:- if(\+ current_op(_, _, '|')).
	:- public(op(1100, xfy, '|')).
:- endif.

[pmoura]

Pushed a Logtalk test that exposes this bug:

$ logtalk_tester -p scryer -s ~/Documents/Logtalk/
% Batch testing started @ 2022-08-15 18:44:28
%         Logtalk version: 3.58.0-b01
%         Scryer Prolog version: 0.9.0
%
% logtalk3/tests/prolog/syntax/operators
%         57 tests: 0 skipped, 56 passed, 1 failed (0 flaky)
%         completed tests from object tests in 9 seconds
%         clause coverage n/a
%
% Compilation errors/warnings and failed unit tests
% (compilation errors/warnings might be expected depending on the test)
!     lgt_operators_57: failure (in 0.0 seconds)
!       test assertion failed: 0>=1001
!       in file logtalk3/tests/prolog/syntax/operators/tests.lgt between lines 238-243
%
% Failed tests
logtalk3/tests/prolog/syntax/operators/tests.lgt - lgt_operators_57 @ tests
%
% 1 test sets: 1 completed, 0 skipped, 0 broken, 0 timedout, 0 crashed
% 57 tests: 0 skipped, 56 passed, 1 failed (0 flaky)
%
% Batch testing ended @ 2022-08-15 18:44:40

[triska]

The same problem is present in master, where we get:

?- current_op(Pre, Fix, '|').
   Pre = 0, Fix = xfy, unexpected
;  false.
?- X = (a|b).
   error(syntax_error(incomplete_reduction),read_term/3:1). % expected
?- use_module(library(dcgs)).
   true.
?- current_op(Pre, Fix, '|').
   Pre = 1105, Fix = xfy % expected
;  false.
?- X = (a|b).
   X = (a | b). % expected

[pmoura]

Thanks for the fix. All tests pass now:

$ logtalk_tester -p scryer -s ~/Documents/Logtalk/
% Batch testing started @ 2022-08-20 15:53:18
%         Logtalk version: 3.58.0-b01
%         Scryer Prolog version: 0.9.0
%
% logtalk3/tests/prolog/syntax/operators
%         57 tests: 1 skipped, 56 passed, 0 failed (0 flaky)
%         completed tests from object tests in 10 seconds
%         clause coverage n/a
%
% Skipped tests
logtalk3/tests/prolog/syntax/operators/tests.lgt - lgt_operators_57 @ tests
%
% 1 test sets: 1 completed, 0 skipped, 0 broken, 0 timedout, 0 crashed
% 57 tests: 1 skipped, 56 passed, 0 failed (0 flaky)
%
% Batch testing ended @ 2022-08-20 15:53:29