swap overload for observer_ptr is not constexpr

[jwakely]

llvm-project/libcxx/test/std/experimental/memory/memory.observer.ptr/swap.pass.cpp

Line 54 in cac806b

std::experimental::swap(ptr1, ptr2);

This test checks that swap is constexpr, which is not the case in the TS:
https://cplusplus.github.io/fundamentals-ts/v3.html#memory.observer.ptr.special

Is this testing an extension?

[frederick-vs-ja]

Looks like that this part of LFTS v3 is not sufficiently rebased onto C++20. IMO the swap function and the comparison operators should be constexpr.

Would an LWG issue be accepted given no future version of LFTS is planned currently?

[jwakely]

I'll open an issue. Even if there's no v4 of LFTS it will be somewhere to make a record of the defect, and whether LWG agrees it should be constexpr (IMHO it should be).

Feel free to close this, I'll add the issue number here later.

[jwakely]

https://cplusplus.github.io/LWG/issue4295

[ldionne]

Closing since this'll come back to us as an LWG issue once it gets voted!