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

[A. Jiang via libcxx-commits]

frederick-vs-ja wrote:

In pre-C++23 modes, our `<cmath>` includes the whole `<cstddef>` and `<type_traits>` by default. I roughly remember that such inclusion was an obstacle. I guess it should be better to still keep the module for the whole `<type_traits>` in `std_core`.

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