[libcxx-commits] [libcxx] [libc++] Implement `std::function_ref` (PR #186692)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

LGTM with FileCheck removed.

Also, as discussed, I'd like to avoid introducing this type as non-experimental right before the LLVM 23 release, to give us at least a bit of baking time in the tree. Therefore, we'll wait until LLVM 23 is branched before we merge this PR.

https://github.com/llvm/llvm-project/pull/186692