[Bug libstdc++/120384] [13/14/15 Regression] _BinaryPredicateConcept checks in std::unique_copy are wrong

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120384

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-15 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:af7c492712edab3bb46d3ad48bdd9ad719b000d7

commit r15-11249-gaf7c492712edab3bb46d3ad48bdd9ad719b000d7
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed May 21 16:57:59 2025 +0100

    libstdc++: Fix concept checks for std::unique_copy [PR120384]

    This looks to have been wrong since r0-125454-gea89b2482f97aa which
    introduced the predefined_ops.h. Since that change, the binary predicate
    passed to std::__unique_copy is _Iter_comp_iter, which takes arguments
    of the iterator type, not the iterator's value type.

    This removes the checks from the __unique_copy overloads and moves them
    into the second overload of std::unique_copy, where we have the original
    binary predicate, not the adapted one from predefined_ops.h.

    The third __unique_copy overload currently checks that the predicate is
    callable with the input range value type and the output range value
    type. This change alters that, so that we only ever check that the
    predicate can be called with two arguments of the same type. That is
    intentional, because calling the predicate with different types is a bug
    that will be fixed in a later commit (see PR libstdc++/120386).

    libstdc++-v3/ChangeLog:

            PR libstdc++/120384
            * include/bits/stl_algo.h (__unique_copy): Remove all
            _BinaryPredicateConcept concept checks.
            (unique_copy): Check _BinaryPredicateConcept in overload that
            takes a predicate.
            * testsuite/25_algorithms/unique_copy/120384.cc: New test.

    Reviewed-by: Tomasz KamiÅski <tkaminsk@redhat.com>
    (cherry picked from commit 1bb7a195e7cf95537534a42e7aa8705cc78eba4e)