[libcxx-commits] [libcxx] [libc++] Implement LWG4072: std::optional comparisons: constrain harder (PR #209968)

[A. Jiang via libcxx-commits]

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frederick-vs-ja wrote:

Mostly LGTM now. I think we should use the trait declared above. Same for other files.

IMO, in a follow-up PR, we should make these tested in C++17 mode.
```suggestion
  if constexpr (has_cmp_lteq<const T&, const U&>) {
```

https://github.com/llvm/llvm-project/pull/209968