[libcxx-commits] [libcxx] [libc++] Disable mistakenly enabled `optional<T&>` constructors for `optional<T>` (PR #194446)

[A. Jiang via libcxx-commits]

================
@@ -893,6 +893,10 @@ private:
   template <class _Up>
   constexpr static bool __libcpp_opt_ref_ctor_deleted =
       is_lvalue_reference_v<_Tp> && reference_constructs_from_temporary_v<_Tp, _Up>;
+
+  template <class _Up>
+  constexpr static bool __libcpp_enable_opt_ref_ctor =
----------------
frederick-vs-ja wrote:

I don't think we need the `__libcpp` prefix. IIUC, the `__libcpp` prefix is used for avoid conflict with built-ins, standard (including POSIX) names, and some common extensions. In `optional`, perhaps we can just use `__ref_ctor_enabled`.

(Same for `__libcpp_opt_ref_ctor_deleted`, but that's pre-existing and possibly should be changed in another PR.)

https://github.com/llvm/llvm-project/pull/194446