[libcxx-commits] [libcxx] [libc++] Correct `optional<T&>` implementation (PR #174537)

[William Tran-Viet via libcxx-commits]

================
@@ -12,9 +12,10 @@
 #include "test_allocator.h"
 #include <type_traits>
 #include <tuple>
+#include "test_macros.h"
 
 // Types that can be used to test copy/move operations
-
+#if TEST_STD_VER >= 23
----------------
smallp-o-p wrote:

Sorry, I should've specified: I added this to the regular `optional` tests, which are ran in C++17, and the header uses concepts and I believe defaulted constexpr constructors which are not allowed before C++23. 

`error: defaulted definition of default constructor cannot be marked constexpr before C++23`

I suppose I could just move the includes where I use them into the `#if TEST_STD_VER >= 26` guard.

https://github.com/llvm/llvm-project/pull/174537