[libcxx-commits] [libcxx] [libc++] Reimplement `optional<T&>` as a partial specialization (PR #201983)

[A. Jiang via libcxx-commits]

frederick-vs-ja wrote:

> CC @frederick-vs-ja Thoughts on backporting this if it's good to merge?

@ldionne WDYT? There're currently some bugs in `optional<T&>` and it might be preferable to backport this PR for easing future fix backport.

https://github.com/llvm/llvm-project/pull/201983