--- a/libcxx/include/__algorithm/ranges_mismatch.h	Wed Nov 09 17:47:54 2022 +0900
+++ b/libcxx/include/__algorithm/ranges_mismatch.h	Fri Aug 18 09:04:13 2023 +0900
@@ -27,7 +27,7 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if _LIBCPP_STD_VER > 17
+#if _LIBCPP_STD_VER >= 20
 
 namespace ranges {
 
@@ -36,12 +36,9 @@
 
 namespace __mismatch {
 struct __fn {
-  template <class _I1, class _S1, class _I2, class _S2,
-            class _Pred, class _Proj1, class _Proj2>
-  static _LIBCPP_HIDE_FROM_ABI constexpr
-  mismatch_result<_I1, _I2>
-  __go(_I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2,
-       _Pred& __pred, _Proj1& __proj1, _Proj2& __proj2) {
+  template <class _I1, class _S1, class _I2, class _S2, class _Pred, class _Proj1, class _Proj2>
+  static _LIBCPP_HIDE_FROM_ABI constexpr mismatch_result<_I1, _I2>
+  __go(_I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2, _Pred& __pred, _Proj1& __proj1, _Proj2& __proj2) {
     while (__first1 != __last1 && __first2 != __last2) {
       if (!std::invoke(__pred, std::invoke(__proj1, *__first1), std::invoke(__proj2, *__first2)))
         break;
@@ -51,34 +48,41 @@
     return {std::move(__first1), std::move(__first2)};
   }
 
-  template <input_iterator _I1, sentinel_for<_I1> _S1,
-            input_iterator _I2, sentinel_for<_I2> _S2,
-            class _Pred = ranges::equal_to, class _Proj1 = identity, class _Proj2 = identity>
+  template <input_iterator _I1,
+            sentinel_for<_I1> _S1,
+            input_iterator _I2,
+            sentinel_for<_I2> _S2,
+            class _Pred  = ranges::equal_to,
+            class _Proj1 = identity,
+            class _Proj2 = identity>
     requires indirectly_comparable<_I1, _I2, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
-  mismatch_result<_I1, _I2> operator()(_I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2,
-                                       _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr mismatch_result<_I1, _I2> operator()(
+      _I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2, _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {})
+      const {
     return __go(std::move(__first1), __last1, std::move(__first2), __last2, __pred, __proj1, __proj2);
   }
 
-  template <input_range _R1, input_range _R2,
-            class _Pred = ranges::equal_to, class _Proj1 = identity, class _Proj2 = identity>
+  template <input_range _R1,
+            input_range _R2,
+            class _Pred  = ranges::equal_to,
+            class _Proj1 = identity,
+            class _Proj2 = identity>
     requires indirectly_comparable<iterator_t<_R1>, iterator_t<_R2>, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
-  mismatch_result<borrowed_iterator_t<_R1>, borrowed_iterator_t<_R2>>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr mismatch_result<borrowed_iterator_t<_R1>,
+                                                                        borrowed_iterator_t<_R2>>
   operator()(_R1&& __r1, _R2&& __r2, _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
-    return __go(ranges::begin(__r1), ranges::end(__r1), ranges::begin(__r2), ranges::end(__r2),
-                __pred, __proj1, __proj2);
+    return __go(
+        ranges::begin(__r1), ranges::end(__r1), ranges::begin(__r2), ranges::end(__r2), __pred, __proj1, __proj2);
   }
 };
 } // namespace __mismatch
 
 inline namespace __cpo {
-  constexpr inline auto mismatch = __mismatch::__fn{};
+constexpr inline auto mismatch = __mismatch::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
-#endif // _LIBCPP_STD_VER > 17
+#endif // _LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD