[Bug libstdc++/108362] views::istream is SFINAE-unfriendly

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108362

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:7d0cddced0ff101f5f59ceb2a45e7f145ff973ac

commit r12-9496-g7d0cddced0ff101f5f59ceb2a45e7f145ff973ac
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Mar 9 13:35:04 2023 -0500

    libstdc++: Make views::single/iota/istream SFINAE-friendly [PR108362]

            PR libstdc++/108362

    libstdc++-v3/ChangeLog:

            * include/std/ranges (__detail::__can_single_view): New concept.
            (_Single::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            (__detail::__can_iota_view): New concept.
            (_Iota::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            (__detail::__can_istream_view): New concept.
            (_Istream::operator()): Constrain it.  Move [[nodiscard]] to the
            end of the function declarator.
            * testsuite/std/ranges/iota/lwg3292_neg.cc: Prune "in
            requirements" diagnostic.
            * testsuite/std/ranges/iota/iota_view.cc (test07): New test.
            * testsuite/std/ranges/istream_view.cc (test08): New test.
            * testsuite/std/ranges/single_view.cc (test07): New test.

    (cherry picked from commit 95827e1b9f7d5dd5a697bd60292e3876a7e8c15c)