[Bug libstdc++/102270] std::tuple<>::swap missing constexpr specifier

[hewillk at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102270

--- Comment #2 from 康桓瑋 <hewillk at gmail dot com> ---
In addition, the uses-allocator construction version also missing constexpr
specifier, but I don't know if this is intentional.

#include <tuple>
#include <memory>

struct O {
  using allocator_type = std::allocator<int>;
  O() = default;
  constexpr O(const allocator_type&) {}
};

constexpr std::allocator<int> a;
constexpr std::tuple<O> t(std::allocator_arg, a);

https://godbolt.org/z/ba61nWhYx