cebb2dd068
We have weaned ourselves off of qExchange(), which, however, has C++23 semantics (is constexpr and noexcept), while we only require C++17 atm. At the same time, we have more and more uses of a constexpr exchange(), iow: the C++20 extension. We have the qNN namespaces for this, so let's use it: Add q20::exchange(), with C++20 semantics (constexpr, not noexcept), and use it to port the only remaining qExchange() user (since ported to 2×std::move() to make the header compatible with QT_NO_QEXCHANGE), QScopedValueRollback. No user requires the C++23 noexcept on the function (compilers will figure it out, because the std::exchange is fully inline), and we can't provide a q23::exchange() even if we needed to, because the author of P2401 forgot to ask to update the value of __cpp_lib_exchange_function... Fixes: QTBUG-133038 Pick-to: 6.8 Change-Id: I003df445001d1c5ab02402119c5e5106aa156263 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> (cherry picked from commit b5ed7fb203335cef7b7b4f70f4130b07166cecf2) Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>