Careful with op/3

General
2

Or maybe the check is more difficult to perform
in a module context? Similar problem like here:

Only with infix and postfix for operators, instead of
static and built_in for predicates.

On the other hand I remember SWI-Prolog being
quite strict about ambiguous import of predicates.

Edit 09.04.2022:
Now I found a test case where SWI-Prolog and
Scryer Prolog differ in parsing:

/* SWI-Prolog */
?- op(9,fy,fy), op(9,yfx,yfx).
true.

?- X = (fy 1 yfx 2), write_canonical(X), nl.
yfx(fy(1),2)

But then:

/* Scryer Prolog */
?- op(9,fy,fy), op(9,yfx,yfx).
   true.

?- X = (fy 1 yfx 2), write_canonical(X), nl.
fy(yfx(1,2))

Was worried what Dogelog Player does. But it seems Dogelog Player
sides with Scryer Prolog, also GNU Prolog, Tau Prolog and
formerly Jekejeke Prolog do.