[libcxx-commits] [libcxx] [libc++] Implement P3379R0 Constrain `std::expected` equality operators (PR #135759)

[A. Jiang via libcxx-commits]

================
@@ -1139,8 +1140,12 @@ class expected : private __expected_base<_Tp, _Err> {
 
   // [expected.object.eq], equality operators
   template <class _T2, class _E2>
-    requires(!is_void_v<_T2>)
-  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const expected& __x, const expected<_T2, _E2>& __y) {
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const expected& __x, const expected<_T2, _E2>& __y)
+    requires(!is_void_v<_T2>) && requires {
+      { *__x == *__y } -> __boolean_testable;
----------------
frederick-vs-ja wrote:

Yeah. Let's do this for C++26 first. FWIW I encountered inconsistent responses from MSVC STL team (microsoft/STL#4847, microsoft/STL#5272).

https://github.com/llvm/llvm-project/pull/135759