Compiler warning when using "std::optional" as field

[omarmed]

Using "std::optional" within an aggregate causes a warning.

Example: [(https://godbolt.org/z/5W19cYG6d)]

#include <iostream>
#include <optional>
#include <https://raw.githubusercontent.com/boost-ext/reflect/main/reflect>

struct Prueba {
    std::optional<int> v;
};

int main() {
    auto p = Prueba{};
    reflect::for_each([&](auto I) {
        std::cout << reflect::member_name<I>(p) << " = " << typeid(reflect::get<I>(p)).name() << std::endl;
    }, p);

    return 0;
}

Compiler output:

/app/raw.githubusercontent.com/boost-ext/reflect/main/reflect:88:42: warning: inline function 'reflect::detail::any::operator int<int>' is not defined [-Wundefined-inline]
   88 | struct any { template<class T> constexpr operator T() const noexcept; };
      |                                          ^
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/14.0.1/../../../../include/c++/14.0.1/optional:210:17: note: used here
  210 |             : _M_value(std::forward<_Args>(__args)...)
      |                        ^
1 warning generated.

It's just a warning, and the program works correctly, but it gives problems when using "-Werror"