[libc++] Add ranges::max_element to the synopsis and ADL-proof the __min_element_impl calls

[ldionne]

libcxx/include/__algorithm/ranges_max_element.h

39

Can we add tests?

[ldionne]

LGTM with tests. We have several ADL proofing tests, see for example libcxx/test/std/strings/basic.string/string.modifiers/robust_against_adl.pass.cpp.

[ldionne]

@philnik just made me aware of https://wg21.link/P2538, so we can't use ADL-proof tests. Hence LGTM as-is.

libcxx/include/__algorithm/ranges_max_element.h

 namespace ranges {
 namespace __max_element {
 struct __fn {
   template <forward_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
             indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
   _LIBCPP_HIDE_FROM_ABI constexpr
   _Ip operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };
-    return __min_element_impl(__first, __last, __comp_lhs_rhs_swapped, __proj);
+    return ranges::__min_element_impl(__first, __last, __comp_lhs_rhs_swapped, __proj);
   }
 
   template <forward_range _Rp, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
   _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Rp> operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };
-    return __min_element_impl(ranges::begin(__r), ranges::end(__r), __comp_lhs_rhs_swapped, __proj);
+    return ranges::__min_element_impl(ranges::begin(__r), ranges::end(__r), __comp_lhs_rhs_swapped, __proj);
   }
 };
 } // namespace __max_element
 
 inline namespace __cpo {
   inline constexpr auto max_element = __max_element::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
 
 #endif // _LIBCPP___ALGORITHM_RANGES_MAX_ELEMENT_H

libcxx/include/algorithm

namespace ranges {
   template<forward_iterator I, sentinel_for<I> S, class Proj = identity,
     indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less>             // since C++20
   constexpr I min_element(I first, S last, Comp comp = {}, Proj proj = {});
 
   template<forward_range R, class Proj = identity,
     indirect_strict_weak_order<projected<iterator_t<R>, Proj>> Comp = ranges::less> // since C++20
   constexpr borrowed_iterator_t<R> min_element(R&& r, Comp comp = {}, Proj proj = {});
 
+  template<forward_iterator I, sentinel_for<I> S, class Proj = identity,
+    indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less>
+  constexpr I ranges::max_element(I first, S last, Comp comp = {}, Proj proj = {});                        // since C++20
+
+  template<forward_range R, class Proj = identity,
+    indirect_strict_weak_order<projected<iterator_t<R>, Proj>> Comp = ranges::less>
+  constexpr borrowed_iterator_t<R> ranges::max_element(R&& r, Comp comp = {}, Proj proj = {});             // since C++20
+
+
   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>
   constexpr mismatch_result<_I1, _I2>
   mismatch()(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) // since C++20
 
   template <input_range R1, input_range R2,
           class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>