On Tue, Nov 28, 2023 at 12:34 PM Jonathan Wakely wrote:
>
> You can just move the contained value to another object which you don't destroy. This doesn't need to be added to std::optional.
Your edict is discriminatory against enthusiasts of unmovable
user-defined classes:
#include <mutex>
#include <optional>
std::mutex dummy1;
alignas(std::mutex) char unsigned dummy2[sizeof(std::mutex)];
int main(void)
{
std::optional< std::mutex > var;
var.emplace();
dummy1 = std::move( var.value() ); // doesn't work
::new(dummy2) std::mutex( std::move(var.value()) ); // doesn't work
}
So just construct a new object over the old one, e.g.
std::construct_at(&var);
This abandons the old one and creates a new empty optional over it.
There's no need to add a new member function for this niche use case.