Thanks for the very quick fix - it's a great feeling to report a problem
and get it fixed this quickly.

I can confirm that the fix solves not only the small reproducer but also
the original problems I got when trying to install our (large) system
on PostgreSQL 19 devel for testing.

We actually ran into the same problem in two ways:
* the reordered FK with datatype mismatch (my reproducer)
* other reordered FKs with the same datatypes, where we instead got
  regular FK violations

In case you want a reproducer for the second case as well, I've included it below,
but perhaps it's not relevant since the patch already fixed it.

----
drop table if exists parent, child;

create table parent (
     c1 integer,
     c2 integer,
     primary key (c1, c2)
);

create table child (
     c1 integer,
     c2 integer,
     constraint child_fk foreign key (c2, c1) references parent (c2, c1)
);

insert into parent (c1, c2) values (1, 2);
insert into child (c1, c2) values (1, 2);

/Fredrik Widlert