[libcxx-commits] [libcxx] [libc++] Implement the `<type_traits>` parts of P1317R2 (PR #151480)

[Louis Dionne via libcxx-commits]

ldionne wrote:

>From #110501 

> Second, we create a top-level std_core module that contains several dependency-free utilities used (directly or indirectly) from the `__math` subdirectory. This is needed because `__math` pulls in a bunch of stuff, and `__math` is used from the C compatibility header `<math.h>`.

So as long as we don't move something that's used by `__math` back into `std` (which would create a cycle), we should be OK.

https://github.com/llvm/llvm-project/pull/151480