[Bug libstdc++/100384] Compiling in c++17 mode breaks compilation of functions named visit()

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100384

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<r...@gcc.gnu.org>:

https://gcc.gnu.org/g:8ad4d9b46944db1be6f1b216b5b8e74bd9f66937

commit r10-9937-g8ad4d9b46944db1be6f1b216b5b8e74bd9f66937
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Tue May 4 12:16:46 2021 +0100

    libstdc++: Do not use deduced return type for std::visit [PR 100384]

    This avoids errors outside the immediate context when std::visit is an
    overload candidate because of ADL, but not actually viable.

    The solution is to give std::visit a non-deduced return type. New
    helpers are introduced for that, and existing ones refactored slightly.

    libstdc++-v3/ChangeLog:

            PR libstdc++/100384
            * include/std/variant (__get_t): New alias template yielding the
            return type of std::get<N> on a variant.
            (__visit_result_t): New alias template yielding the result of
            std::visit.
            (__same_types): Move into namespace __detail::__variant.
            (__check_visitor_results): Likewise. Use __invoke_result_t and
            __get_t.
            (__check_visitor_result): Remove.
            (visit): Use __visit_result_t for return type.
            * testsuite/20_util/variant/100384.cc: New test.

    (cherry picked from commit af5b2b911dd80ae9cc87404b7e7ab807cf6655d4)