[libc++][ranges] Implement `std::ranges::partial_sort_copy`.

[var-const]

Summary

ranges::partial_sort_copy feedback.

libcxx/docs/Status/RangesAlgorithms.csv

 Write,replace_copy,Nikolas Klauser,`D129806 <https://llvm.org/D129806>`_,Under review
 Write,replace_copy_if,Nikolas Klauser,`D129806 <https://llvm.org/D129806>`_,Under review
 Write,swap_ranges,Nikolas Klauser,`D116303 <https://llvm.org/D116303>`_,✅
 Write,reverse_copy,Nikolas Klauser,`D127211 <https://llvm.org/D127211>`_,✅
 Write,rotate_copy,Nikolas Klauser,`D127211 <https://llvm.org/D127211>`_,✅
 Write,sample,Not assigned,n/a,Not started
 Write,unique_copy,Not assigned,n/a,Not started
 Write,partition_copy,Konstantin Varlamov,`D130070 <https://llvm.org/D130070>`_,✅
-Write,partial_sort_copy,Konstantin Varlamov,n/a,In progress
+Write,partial_sort_copy,Konstantin Varlamov,`D130532 <https://llvm.org/D130532>`_,✅
 Merge,merge,Hui Xie,`D128611 <https://llvm.org/D128611>`_,✅
 Merge,set_difference,Hui Xie,`D128983 <https://llvm.org/D128983>`_,✅
 Merge,set_intersection,Hui Xie,`D129233 <https://llvm.org/D129233>`_,✅
 Merge,set_symmetric_difference,Hui Xie,`D129520 <https://llvm.org/D129520>`_,✅
 Merge,set_union,Hui Xie,`D129657 <https://llvm.org/D129657>`_,✅
 Permutation,remove,Nikolas Klauser,`D128618 <https://llvm.org/D128618>`_,✅
 Permutation,remove_if,Nikolas Klauser,`D128618 <https://llvm.org/D128618>`_,✅
 Permutation,reverse,Nikolas Klauser,`D125752 <https://llvm.org/D125752>`_,✅

libcxx/include/__algorithm/make_heap.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare& __comp) {
+void __make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare&& __comp) {
   using _CompRef = typename __comp_ref_type<_Compare>::type;
   _CompRef __comp_ref = __comp;
 
   using difference_type = typename iterator_traits<_RandomAccessIterator>::difference_type;
   difference_type __n = __last - __first;
   if (__n > 1) {
     // start from the first parent, there is no need to consider children
     for (difference_type __start = (__n - 2) / 2; __start >= 0; --__start) {

libcxx/include/__algorithm/make_projected.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___ALGORITHM_MAKE_PROJECTED_H
 #define _LIBCPP___ALGORITHM_MAKE_PROJECTED_H
 
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__functional/identity.h>
 #include <__functional/invoke.h>
 #include <__type_traits/decay.h>
+#include <__type_traits/enable_if.h>
 #include <__type_traits/is_member_pointer.h>
 #include <__utility/forward.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Comp, class _Proj>
+struct _ProjectedComp {
+  _Comp& __comp;
+  _Proj& __proj;
+
+  _LIBCPP_CONSTEXPR _ProjectedComp(_Comp& __c, _Proj& __p) : __comp(__c), __proj(__p) {}
+
+  template <class _T1, class _T2>
+  typename __invoke_of<_Comp&,
+                       decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T1>())),
+                       decltype(std::__invoke(std::declval<_Proj&>(), std::declval<_T2>()))
+  >::type
+  _LIBCPP_CONSTEXPR operator()(_T1&& __lhs, _T2&& __rhs) const {
+    return std::__invoke(__comp,
+                      std::__invoke(__proj, std::forward<_T1>(__lhs)),
+                      std::__invoke(__proj, std::forward<_T2>(__rhs)));
+  }
+
+};
+
+template <class _Comp, class _Proj, class = void>
+struct __can_use_pristine_comp : std::false_type {};
+
+template <class _Comp, class _Proj>
+struct __can_use_pristine_comp<_Comp, _Proj, __enable_if_t<
+    !is_member_pointer<typename decay<_Comp>::type>::value && (
+#if _LIBCPP_STD_VER > 17
+      is_same<typename decay<_Proj>::type, identity>::value ||
+#endif
+      is_same<typename decay<_Proj>::type, __identity>::value
+    )
+> > : std::true_type {};
+
+template <class _Comp, class _Proj>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static
+__enable_if_t<
+    !__can_use_pristine_comp<_Comp, _Proj>::value,
+    _ProjectedComp<_Comp, _Proj>
+>
+__make_projected_comp_cxx03(_Comp& __comp, _Proj& __proj) {
+  return _ProjectedComp<_Comp, _Proj>(__comp, __proj);
+}
+
+template <class _Comp, class _Proj, class = __enable_if_t<__can_use_pristine_comp<_Comp, _Proj>::value> >
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR static
+__enable_if_t<
+    __can_use_pristine_comp<_Comp, _Proj>::value,
+    _Comp&
+>
+__make_projected_comp_cxx03(_Comp& __comp, _Proj&) {
+  return __comp;
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 
 template <class _Pred, class _Proj>
 _LIBCPP_HIDE_FROM_ABI constexpr static

libcxx/include/__algorithm/partial_sort.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 

 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator, class _Sentinel>
 _LIBCPP_CONSTEXPR_AFTER_CXX17
 _RandomAccessIterator __partial_sort_impl(
-    _RandomAccessIterator __first, _RandomAccessIterator __middle, _Sentinel __last, _Compare __comp) {
+    _RandomAccessIterator __first, _RandomAccessIterator __middle, _Sentinel __last, _Compare&& __comp) {
   if (__first == __middle) {
     return _IterOps<_AlgPolicy>::next(__middle, __last);
   }
 
   std::__make_heap<_AlgPolicy, _Compare>(__first, __middle, __comp);
 
   typename iterator_traits<_RandomAccessIterator>::difference_type __len = __middle - __first;
   _RandomAccessIterator __i = __middle;
   for (; __i != __last; ++__i)
   {
       if (__comp(*__i, *__first))
       {
           _IterOps<_AlgPolicy>::iter_swap(__i, __first);
-          std::__sift_down<_AlgPolicy, _Compare>(__first, __comp, __len, __first);
+          std::__sift_down<_AlgPolicy>(__first, __comp, __len, __first);
       }
 
   }
   std::__sort_heap<_AlgPolicy, _Compare>(std::move(__first), std::move(__middle), __comp);
 
   return __i;
 }
 

libcxx/include/__algorithm/partial_sort_copy.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___ALGORITHM_PARTIAL_SORT_COPY_H
 #define _LIBCPP___ALGORITHM_PARTIAL_SORT_COPY_H
 
 #include <__algorithm/comp.h>
 #include <__algorithm/comp_ref_type.h>
 #include <__algorithm/iterator_operations.h>
 #include <__algorithm/make_heap.h>
+#include <__algorithm/make_projected.h>
 #include <__algorithm/sift_down.h>
 #include <__algorithm/sort_heap.h>
 #include <__config>
+#include <__functional/identity.h>
+#include <__functional/invoke.h>
 #include <__iterator/iterator_traits.h>
+#include <__type_traits/is_callable.h>
+#include <__utility/move.h>
+#include <__utility/pair.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _AlgPolicy, class _Compare, class _InputIterator, class _RandomAccessIterator>
-_LIBCPP_CONSTEXPR_AFTER_CXX17 _RandomAccessIterator
-__partial_sort_copy(_InputIterator __first, _InputIterator __last,
-                    _RandomAccessIterator __result_first, _RandomAccessIterator __result_last, _Compare __comp)
+template <class _AlgPolicy, class _Compare,
+          class _InputIterator, class _Sentinel1, class _RandomAccessIterator, class _Sentinel2,
+          class _Proj1, class _Proj2>
+_LIBCPP_CONSTEXPR_AFTER_CXX17 pair<_InputIterator, _RandomAccessIterator>
+__partial_sort_copy(_InputIterator __first, _Sentinel1 __last,
+                    _RandomAccessIterator __result_first, _Sentinel2 __result_last,
+                    _Compare&& __comp, _Proj1&& __proj1, _Proj2&& __proj2)
 {
     _RandomAccessIterator __r = __result_first;
+    auto&& __projected_comp = std::__make_projected_comp_cxx03(__comp, __proj2);
+
     if (__r != __result_last)
     {
         for (; __first != __last && __r != __result_last; ++__first, (void) ++__r)
             *__r = *__first;
-        std::__make_heap<_AlgPolicy, _Compare>(__result_first, __r, __comp);
+        std::__make_heap<_AlgPolicy>(__result_first, __r, __projected_comp);
         typename iterator_traits<_RandomAccessIterator>::difference_type __len = __r - __result_first;
         for (; __first != __last; ++__first)
-            if (__comp(*__first, *__result_first))
-            {
+            if (std::__invoke(__comp, std::__invoke(__proj1, *__first), std::__invoke(__proj2, *__result_first))) {
                 *__result_first = *__first;
-                std::__sift_down<_AlgPolicy, _Compare>(__result_first, __comp, __len, __result_first);
+                std::__sift_down<_AlgPolicy>(__result_first, __projected_comp, __len, __result_first);
             }
-        std::__sort_heap<_AlgPolicy, _Compare>(__result_first, __r, __comp);
+        std::__sort_heap<_AlgPolicy>(__result_first, __r, __projected_comp);
     }
-    return __r;
+
+    return pair<_InputIterator, _RandomAccessIterator>(
+        _IterOps<_AlgPolicy>::next(std::move(__first), std::move(__last)), std::move(__r));
 }
 
 template <class _InputIterator, class _RandomAccessIterator, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _RandomAccessIterator
 partial_sort_copy(_InputIterator __first, _InputIterator __last,
                   _RandomAccessIterator __result_first, _RandomAccessIterator __result_last, _Compare __comp)
 {
-    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
-    return std::__partial_sort_copy<_ClassicAlgPolicy, _Comp_ref>(
-        __first, __last, __result_first, __result_last, __comp);
+  static_assert(__is_callable<_Compare, decltype(*__first), decltype(*__result_first)>::value,
+                "Comparator has to be callable");
+
+  using _Comp_ref = typename __comp_ref_type<_Compare>::type;
+  auto __result = std::__partial_sort_copy<_ClassicAlgPolicy>(__first, __last, __result_first, __result_last,
+      static_cast<_Comp_ref>(__comp), __identity(), __identity());
+  return __result.second;
 }
 
 template <class _InputIterator, class _RandomAccessIterator>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _RandomAccessIterator
 partial_sort_copy(_InputIterator __first, _InputIterator __last,
                   _RandomAccessIterator __result_first, _RandomAccessIterator __result_last)
 {
     return _VSTD::partial_sort_copy(__first, __last, __result_first, __result_last,
                                    __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
 }
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_PARTIAL_SORT_COPY_H

libcxx/include/__algorithm/ranges_partial_sort_copy.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___ALGORITHM_RANGES_PARTIAL_SORT_COPY_H
 #define _LIBCPP___ALGORITHM_RANGES_PARTIAL_SORT_COPY_H
 
 #include <__algorithm/in_out_result.h>
+#include <__algorithm/iterator_operations.h>
 #include <__algorithm/make_projected.h>
 #include <__algorithm/partial_sort_copy.h>
 #include <__config>
 #include <__functional/identity.h>
-#include <__functional/invoke.h>
 #include <__functional/ranges_operations.h>
 #include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/projected.h>
 #include <__iterator/sortable.h>
 #include <__ranges/access.h>
 #include <__ranges/concepts.h>
 #include <__ranges/dangling.h>
-#include <__utility/forward.h>
 #include <__utility/move.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
 
template <input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
             random_access_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
             class _Comp = ranges::less, class _Proj1 = identity, class _Proj2 = identity>
   requires indirectly_copyable<_Iter1, _Iter2> && sortable<_Iter2, _Comp, _Proj2> &&
            indirect_strict_weak_order<_Comp, projected<_Iter1, _Proj1>, projected<_Iter2, _Proj2>>
   _LIBCPP_HIDE_FROM_ABI constexpr
   partial_sort_copy_result<_Iter1, _Iter2>
   operator()(_Iter1 __first, _Sent1 __last, _Iter2 __result_first, _Sent2 __result_last,
              _Comp __comp = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
-    // TODO: implement
-    (void)__first; (void)__last; (void)__result_first; (void)__result_last; (void)__comp; (void)__proj1; (void)__proj2;
-    return {};
+    auto __result = std::__partial_sort_copy<_RangeAlgPolicy>(
+        std::move(__first), std::move(__last), std::move(__result_first), std::move(__result_last),
+        __comp, __proj1, __proj2
+    );
+    return {std::move(__result.first), std::move(__result.second)};
   }
 
   template <input_range _Range1, random_access_range _Range2, class _Comp = ranges::less,
             class _Proj1 = identity, class _Proj2 = identity>
   requires indirectly_copyable<iterator_t<_Range1>, iterator_t<_Range2>> &&
            sortable<iterator_t<_Range2>, _Comp, _Proj2> &&
            indirect_strict_weak_order<_Comp, projected<iterator_t<_Range1>, _Proj1>,
                                       projected<iterator_t<_Range2>, _Proj2>>
   _LIBCPP_HIDE_FROM_ABI constexpr
   partial_sort_copy_result<borrowed_iterator_t<_Range1>, borrowed_iterator_t<_Range2>>
   operator()(_Range1&& __range, _Range2&& __result_range, _Comp __comp = {},
              _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
-    // TODO: implement
-    (void)__range; (void)__result_range; (void)__comp; (void)__proj1; (void)__proj2;
-    return {};
+    auto __result = std::__partial_sort_copy<_RangeAlgPolicy>(
+        ranges::begin(__range), ranges::end(__range), ranges::begin(__result_range), ranges::end(__result_range),
+        __comp, __proj1, __proj2
+    );
+    return {std::move(__result.first), std::move(__result.second)};
   }
 
 };
 
 } // namespace __partial_sort_copy
 
 inline namespace __cpo {
   inline constexpr auto partial_sort_copy = __partial_sort_copy::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
 
 #endif // _LIBCPP___ALGORITHM_RANGES_PARTIAL_SORT_COPY_H

libcxx/include/__algorithm/sift_down.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
 _LIBCPP_CONSTEXPR_AFTER_CXX11 void
-__sift_down(_RandomAccessIterator __first, _Compare __comp,
+__sift_down(_RandomAccessIterator __first, _Compare&& __comp,
             typename iterator_traits<_RandomAccessIterator>::difference_type __len,
             _RandomAccessIterator __start)
 {
     using _Ops = _IterOps<_AlgPolicy>;
 
     typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
     typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
     // left-child of __start is at 2 * __start + 1

libcxx/include/__algorithm/sort_heap.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare& __comp) {
+void __sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare&& __comp) {
   using _CompRef = typename __comp_ref_type<_Compare>::type;
   _CompRef __comp_ref = __comp;
 
   using difference_type = typename iterator_traits<_RandomAccessIterator>::difference_type;
   for (difference_type __n = __last - __first; __n > 1; --__last, (void) --__n)
     std::__pop_heap<_AlgPolicy, _CompRef>(__first, __last, __comp_ref, __n);
 }
 

libcxx/include/algorithm

template<input_range R1, input_range R2, class Pred = ranges::equal_to,
   template<input_iterator I, sentinel_for<I> S, class Proj = identity,
            indirect_unary_predicate<projected<I, Proj>> Pred>
     constexpr bool ranges::none_of(I first, S last, Pred pred, Proj proj = {});     // since C++20
 
   template<input_range R, class Proj = identity,
            indirect_unary_predicate<projected<iterator_t<R>, Proj>> Pred>
     constexpr bool ranges::none_of(R&& r, Pred pred, Proj proj = {});               // since C++20
 
+  template<input_iterator I1, sentinel_for<I1> S1,
+          random_access_iterator I2, sentinel_for<I2> S2,
+          class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
+    requires indirectly_copyable<I1, I2> && sortable<I2, Comp, Proj2> &&
+            indirect_strict_weak_order<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
+    constexpr partial_sort_copy_result<I1, I2>
+      partial_sort_copy(I1 first, S1 last, I2 result_first, S2 result_last,
+                        Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});        // Since C++20
+
+  template<input_range R1, random_access_range R2, class Comp = ranges::less,
+          class Proj1 = identity, class Proj2 = identity>
+    requires indirectly_copyable<iterator_t<R1>, iterator_t<R2>> &&
+            sortable<iterator_t<R2>, Comp, Proj2> &&
+            indirect_strict_weak_order<Comp, projected<iterator_t<R1>, Proj1>,
+                                        projected<iterator_t<R2>, Proj2>>
+    constexpr partial_sort_copy_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
+      partial_sort_copy(R1&& r, R2&& result_r, Comp comp = {},
+                        Proj1 proj1 = {}, Proj2 proj2 = {});                        // Since C++20
+
   template<forward_iterator I, sentinel_for<I> S, class Proj = identity,
            indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less>
     constexpr bool ranges::is_sorted(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 bool ranges::is_sorted(R&& r, Comp comp = {}, Proj proj = {});                // since C++20
 

 #include <__algorithm/ranges_minmax.h>
 #include <__algorithm/ranges_minmax_element.h>
 #include <__algorithm/ranges_mismatch.h>
 #include <__algorithm/ranges_move.h>
 #include <__algorithm/ranges_move_backward.h>
 #include <__algorithm/ranges_none_of.h>
 #include <__algorithm/ranges_nth_element.h>
 #include <__algorithm/ranges_partial_sort.h>
+#include <__algorithm/ranges_partial_sort_copy.h>
 #include <__algorithm/ranges_partition.h>
 #include <__algorithm/ranges_partition_copy.h>
 #include <__algorithm/ranges_partition_point.h>
 #include <__algorithm/ranges_pop_heap.h>
 #include <__algorithm/ranges_push_heap.h>
 #include <__algorithm/ranges_remove.h>
 #include <__algorithm/ranges_remove_if.h>
 #include <__algorithm/ranges_replace.h>

libcxx/test/libcxx/algorithms/ranges_robust_against_copying_comparators.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
#endif
     //(void)std::ranges::next_permutation(first, last, Less(&copies)); assert(copies == 0);
     //(void)std::ranges::next_permutation(a, Less(&copies)); assert(copies == 0);
     (void)std::ranges::none_of(first, last, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::none_of(a, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::nth_element(first, mid, last, Less(&copies)); assert(copies == 0);
     (void)std::ranges::nth_element(a, mid, Less(&copies)); assert(copies == 0);
     (void)std::ranges::partial_sort(first, mid, last, Less(&copies)); assert(copies == 0);
     (void)std::ranges::partial_sort(a, mid, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::partial_sort_copy(first, last, first2, mid2, Less(&copies)); assert(copies == 0);
-    //(void)std::ranges::partial_sort_copy(a, b, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::partial_sort_copy(first, last, first2, mid2, Less(&copies)); assert(copies == 0);
+    (void)std::ranges::partial_sort_copy(a, b, Less(&copies)); assert(copies == 0);
     (void)std::ranges::partition(first, last, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::partition(a, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::partition_copy(first, last, first2, last2, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::partition_copy(a, first2, last2, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::partition_point(first, last, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::partition_point(a, UnaryTrue(&copies)); assert(copies == 0);
     (void)std::ranges::pop_heap(first, last, Less(&copies)); assert(copies == 0);
     (void)std::ranges::pop_heap(a, Less(&copies)); assert(copies == 0);

libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
#endif
     //(void)std::ranges::next_permutation(first, last, Less(), Proj(&copies)); assert(copies == 0);
     //(void)std::ranges::next_permutation(a, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::none_of(first, last, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::none_of(a, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::nth_element(first, mid, last, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::nth_element(a, mid, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partial_sort(first, mid, last, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partial_sort(a, mid, Less(), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::partial_sort_copy(first, last, first2, mid2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
-    //(void)std::ranges::partial_sort_copy(a, b, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::partial_sort_copy(first, last, first2, mid2, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::partial_sort_copy(a, b, Less(), Proj(&copies), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partition(first, last, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partition(a, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partition_copy(first, last, first2, last2, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partition_copy(a, first2, last2, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partition_point(first, last, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::partition_point(a, UnaryTrue(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::pop_heap(first, last, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::pop_heap(a, Less(), Proj(&copies)); assert(copies == 0);

libcxx/test/std/algorithms/alg.sorting/alg.sort/partial.sort.copy/ranges_partial_sort_copy.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
 
 // <algorithm>
 
 // template<input_iterator I1, sentinel_for<I1> S1,
-//              random_access_iterator I2, sentinel_for<I2> S2,
-//              class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
-//       requires indirectly_copyable<I1, I2> && sortable<I2, Comp, Proj2> &&
-//                indirect_strict_weak_order<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
-//       constexpr partial_sort_copy_result<I1, I2>
-//         partial_sort_copy(I1 first, S1 last, I2 result_first, S2 result_last,
-//                           Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});                   // Since C++20
+//          random_access_iterator I2, sentinel_for<I2> S2,
+//          class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
+//   requires indirectly_copyable<I1, I2> && sortable<I2, Comp, Proj2> &&
+//            indirect_strict_weak_order<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
+//   constexpr partial_sort_copy_result<I1, I2>
+//     partial_sort_copy(I1 first, S1 last, I2 result_first, S2 result_last,
+//                       Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});               // Since C++20
 //
-//     template<input_range R1, random_access_range R2, class Comp = ranges::less,
-//              class Proj1 = identity, class Proj2 = identity>
-//       requires indirectly_copyable<iterator_t<R1>, iterator_t<R2>> &&
-//                sortable<iterator_t<R2>, Comp, Proj2> &&
-//                indirect_strict_weak_order<Comp, projected<iterator_t<R1>, Proj1>,
-//                                           projected<iterator_t<R2>, Proj2>>
-//       constexpr partial_sort_copy_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
-//         partial_sort_copy(R1&& r, R2&& result_r, Comp comp = {},
-//                           Proj1 proj1 = {}, Proj2 proj2 = {});                                   // Since C++20
+// template<input_range R1, random_access_range R2, class Comp = ranges::less,
+//          class Proj1 = identity, class Proj2 = identity>
+//   requires indirectly_copyable<iterator_t<R1>, iterator_t<R2>> &&
+//            sortable<iterator_t<R2>, Comp, Proj2> &&
+//            indirect_strict_weak_order<Comp, projected<iterator_t<R1>, Proj1>,
+//                                       projected<iterator_t<R2>, Proj2>>
+//   constexpr partial_sort_copy_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
+//     partial_sort_copy(R1&& r, R2&& result_r, Comp comp = {},
+//                       Proj1 proj1 = {}, Proj2 proj2 = {});                               // Since C++20
 
 #include <algorithm>
 #include <array>
 #include <concepts>
 #include <functional>
 #include <ranges>
+#include <utility>
 
 #include "almost_satisfies_types.h"
 #include "test_iterators.h"
 
-// TODO: SFINAE tests.
+// Test constraints of the (iterator, sentinel) overload.
+// ======================================================
+
+template <class Iter1 = int*, class Sent1 = int*, class Iter2 = int*, class Sent2 = int*,
+          class Comp = std::ranges::less>
+concept HasPartialSortCopyIter =
+    requires(Iter1&& first1, Sent1&& last1, Iter2&& first2, Sent2&& last2, Comp&& comp) {
+      std::ranges::partial_sort_copy(std::forward<Iter1>(first1), std::forward<Sent1>(last1),
+          std::forward<Iter2>(first2), std::forward<Sent2>(last2), std::forward<Comp>(comp));
+    };
+
+static_assert(HasPartialSortCopyIter<int*, int*, int*, int*, std::ranges::less>);
+
+// !input_iterator<I1>
+static_assert(!HasPartialSortCopyIter<InputIteratorNotDerivedFrom>);
+static_assert(!HasPartialSortCopyIter<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasPartialSortCopyIter<InputIteratorNotInputOrOutputIterator>);
+
+// !sentinel_for<S1, I1>
+static_assert(!HasPartialSortCopyIter<int*, SentinelForNotSemiregular>);
+static_assert(!HasPartialSortCopyIter<int*, SentinelForNotWeaklyEqualityComparableWith>);
+
+// !random_access_iterator<I2>
+static_assert(!HasPartialSortCopyIter<int*, int*, RandomAccessIteratorNotDerivedFrom>);
+static_assert(!HasPartialSortCopyIter<int*, int*, RandomAccessIteratorBadIndex>);
+
+// !sentinel_for<S2, I2>
+static_assert(!HasPartialSortCopyIter<int*, int*, int*, SentinelForNotSemiregular>);
+static_assert(!HasPartialSortCopyIter<int*, int*, int*, SentinelForNotWeaklyEqualityComparableWith>);
+
+// !indirect_unary_predicate<projected<I, Proj>>
+static_assert(!HasPartialSortCopyIter<int*, int*, int*, int*, IndirectUnaryPredicateNotPredicate>);
+static_assert(!HasPartialSortCopyIter<int*, int*, int*, int*, IndirectUnaryPredicateNotCopyConstructible>);
+
+struct Uncopyable {
+  Uncopyable(int&&);
+  Uncopyable(const int&) = delete;
+};
+// !indirectly_copyable<I1, I2>
+static_assert(!HasPartialSortCopyIter<int*, int*, Uncopyable*>);
+
+// !sortable<I2, Comp, Proj2>
+static_assert(!HasPartialSortCopyIter<int*, int*, const int*, const int*>);
+
+struct NoComparator {};
+// !indirect_strict_weak_order<Comp, projected<I1, Proj1>, projected<I2, Proj2>>
+static_assert(!HasPartialSortCopyIter<NoComparator*, NoComparator*, NoComparator*, NoComparator*>);
+
+// Test constraints of the (range) overload.
+// ======================================================
+
+template <class T>
+using R = UncheckedRange<T>;
+
+template <class Range1 = R<int*>, class Range2 = R<int*>, class Comp = std::ranges::less>
+concept HasPartialSortCopyRange =
+    requires(Range1&& range1, Range2&& range2, Comp&& comp) {
+      std::ranges::partial_sort_copy(std::forward<Range1>(range1), std::forward<Range2>(range2),
+          std::forward<Comp>(comp));
+    };
+
+static_assert(HasPartialSortCopyRange<R<int*>, R<int*>, std::ranges::less>);
+
+// !input_range<R1>
+static_assert(!HasPartialSortCopyRange<InputRangeNotDerivedFrom>);
+static_assert(!HasPartialSortCopyRange<InputRangeNotIndirectlyReadable>);
+static_assert(!HasPartialSortCopyRange<InputRangeNotInputOrOutputIterator>);
+
+// !random_access_range<R2>
+static_assert(!HasPartialSortCopyRange<R<int*>, RandomAccessRangeNotDerivedFrom>);
+static_assert(!HasPartialSortCopyRange<R<int*>, RandomAccessRangeBadIndex>);
+
+// !indirectly_copyable<iterator_t<R1>, iterator_t<R2>>
+static_assert(!HasPartialSortCopyRange<R<int*>, R<Uncopyable*>>);
+
+// !sortable<iterator_t<R2>, Comp, Proj2>
+static_assert(!HasPartialSortCopyRange<R<int*>, R<const int*>>);
+
+// !indirect_strict_weak_order<Comp, projected<iterator_t<R1>, Proj1>, projected<iterator_t<R2>, Proj2>>
+static_assert(!HasPartialSortCopyRange<R<NoComparator*>, R<NoComparator*>>);
+
+static_assert(std::is_same_v<std::ranges::partial_sort_copy_result<int, int>, std::ranges::in_out_result<int, int>>);
+
+template <class Iter, class Sent, class OutIter, class OutSent, size_t N>
+constexpr void test_one(
+    std::array<int, N> input, size_t input_size, size_t output_size, std::array<int, N> sorted) {
+  assert(input_size <= N);
+  assert(output_size <= N + 1); // To support testing the case where output size exceeds input size.
+
+  using ResultT = std::ranges::partial_sort_copy_result<Iter, OutIter>;
+  // To support testing the case where output size exceeds input size; also makes sure calling `out.data() + int()` is
+  // valid.
+  constexpr size_t OutputSize = N + 1;
+  size_t result_size = std::ranges::min(input_size, output_size);
+
+  auto begin = input.data();
+  auto end = input.data() + input_size;
+
+  { // (iterator, sentinel) overload.
+    std::array<int, OutputSize> out;
+    auto out_begin = out.data();
+    auto out_end = out.data() + output_size;
+
+    std::same_as<ResultT> decltype(auto) result = std::ranges::partial_sort_copy(
+        Iter(begin), Sent(Iter(end)), OutIter(out_begin), OutSent(OutIter(out_end)));
+
+    assert(base(result.in) == input.data() + input_size);
+    assert(base(result.out) == out.data() + result_size);
+
+    assert(std::ranges::equal(std::ranges::subrange(out.begin(), out.begin() + result_size),
+           std::ranges::subrange(sorted.begin(), sorted.begin() + result_size)));
+  }
+
+  { // (range) overload.
+    std::array<int, OutputSize> out;
+    auto out_begin = out.data();
+    auto out_end = out.data() + output_size;
+    auto in_range = std::ranges::subrange(Iter(begin), Sent(Iter(end)));
+    auto out_range = std::ranges::subrange(OutIter(out_begin), OutSent(OutIter(out_end)));
+
+    std::same_as<ResultT> decltype(auto) result = std::ranges::partial_sort_copy(in_range, out_range);
+
+    assert(base(result.in) == input.data() + input_size);
+    assert(base(result.out) == out.data() + result_size);
+
+    assert(std::ranges::equal(std::ranges::subrange(out.begin(), out.begin() + result_size),
+           std::ranges::subrange(sorted.begin(), sorted.begin() + result_size)));
+  }
+
+}
+
+template <class Iter, class Sent, class OutIter, class OutSent, size_t N>
+constexpr void test_all_subsequences(const std::array<int, N> input) {
+  auto sorted = input;
+  std::sort(sorted.begin(), sorted.end());
+
+  // Whole input, increasing output size. Also check the case when `output_size` exceeds input size.
+  for (size_t out_size = 0; out_size <= N + 1; ++out_size) {
+    test_one<Iter, Sent, OutIter, OutSent>(input, N, out_size, sorted);
+  }
+}
+
+template <class InIter, class Sent1, class OutIter, class Sent2>
+constexpr void test_iterators_in_sent1_out_sent2() {
+  // Empty sequence.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2, 0>({});
+
+  // 1-element sequence.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{1});
+
+  // 2-element sequence.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{2, 1});
+
+  // 3-element sequence.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{2, 1, 3});
+
+  // Longer sequence.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{2, 1, 3, 6, 8, 4, 11, 5});
+
+  // Longer sequence with duplicates.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{2, 1, 3, 6, 2, 8, 6});
+
+  // All elements are the same.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{1, 1, 1});
+
+  // Already sorted.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{1, 2, 3, 4, 5});
+
+  // Descending.
+  test_all_subsequences<InIter, Sent1, OutIter, Sent2>(std::array{5, 4, 3, 2, 1});
+}
+
+template <class InIter, class Sent1, class OutIter>
+constexpr void test_iterators_in_sent1_out() {
+  test_iterators_in_sent1_out_sent2<InIter, Sent1, OutIter, OutIter>();
+  test_iterators_in_sent1_out_sent2<InIter, Sent1, OutIter, sentinel_wrapper<OutIter>>();
+}
+
+template <class InIter, class Sent1>
+constexpr void test_iterators_in_sent1() {
+  test_iterators_in_sent1_out<InIter, Sent1, random_access_iterator<int*>>();
+}
+
+template <class InIter>
+constexpr void test_iterators_in() {
+  if constexpr (std::sentinel_for<InIter, InIter>) {
+    test_iterators_in_sent1<InIter, InIter>();
+  }
+  test_iterators_in_sent1<InIter, sentinel_wrapper<InIter>>();
+}
+
+constexpr void test_iterators() {
+  test_iterators_in<cpp20_input_iterator<int*>>();
+  // Omitting other iterator types to reduce the combinatorial explosion.
+  test_iterators_in<random_access_iterator<int*>>();
+  test_iterators_in<const int*>();
+}
 
 constexpr bool test() {
-  // TODO: main tests.
-  // TODO: A custom comparator works.
-  // TODO: A custom projection works.
+  test_iterators();
+
+  { // A custom comparator works.
+    const std::array in = {1, 2, 3, 4, 5};
+    std::ranges::greater comp;
+
+    {
+      std::array<int, 2> out;
+
+      auto result = std::ranges::partial_sort_copy(in.begin(), in.end(), out.begin(), out.end(), comp);
+      assert(std::ranges::equal(std::ranges::subrange(out.begin(), result.out), std::array{5, 4}));
+    }
+
+    {
+      std::array<int, 2> out;
+
+      auto result = std::ranges::partial_sort_copy(in, out, comp);
+      assert(std::ranges::equal(std::ranges::subrange(out.begin(), result.out), std::array{5, 4}));
+    }
+  }
+
+  { // A custom projection works.
+    struct A {
+      int a;
+
+      constexpr A() = default;
+      constexpr A(int value) : a(value) {}
+      constexpr auto operator<=>(const A&) const = default;
+    };
+
+    const std::array in = {2, 1, 3};
+    auto proj1 = [](int value) { return value * -1; };
+    auto proj2 = [](A value) { return value.a * -1; };
+    // The projections negate the argument, so the array will appear to be sorted in descending order: [3, 2, 1]
+    // (the projections make it appear to the algorithm as [-3, -2, -1]).
+
+    {
+      std::array<A, 2> out;
+
+      // No projections: ascending order.
+      auto result = std::ranges::partial_sort_copy(in.begin(), in.end(), out.begin(), out.end(), {});
+      assert(std::ranges::equal(std::ranges::subrange(out.begin(), result.out), std::array{1, 2}));
+      // Using projections: descending order.
+      result = std::ranges::partial_sort_copy(in.begin(), in.end(), out.begin(), out.end(), {}, proj1, proj2);
+      assert(std::ranges::equal(std::ranges::subrange(out.begin(), result.out), std::array{3, 2}));
+    }
+
+    {
+      std::array<int, 2> out;
+
+      auto result = std::ranges::partial_sort_copy(in, out, {});
+      assert(std::ranges::equal(std::ranges::subrange(out.begin(), result.out), std::array{1, 2}));
+      result = std::ranges::partial_sort_copy(in, out, {}, proj1, proj2);
+      assert(std::ranges::equal(std::ranges::subrange(out.begin(), result.out), std::array{3, 2}));
+    }
+  }
 
   return true;
 }
 
 int main(int, char**) {
   test();
   static_assert(test());
 
   return 0;
 }

libcxx/test/std/algorithms/ranges_result_alias_declarations.compile.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 

 static_assert(std::is_same_v<in_in_result<int, long>, swap_ranges_result<int, long>>);
 
 static_assert(std::is_same_v<in_out_result<int, long>, copy_result<int, long>>);
 static_assert(std::is_same_v<in_out_result<int, long>, copy_n_result<int, long>>);
 static_assert(std::is_same_v<in_out_result<int, long>, copy_if_result<int, long>>);
 static_assert(std::is_same_v<in_out_result<int, long>, copy_backward_result<int, long>>);
 static_assert(std::is_same_v<in_out_result<int, long>, move_result<int, long>>);
 static_assert(std::is_same_v<in_out_result<int, long>, move_backward_result<int, long>>);
-// static_assert(std::is_same_v<in_out_result<int, long>, partial_sort_copy_result<int, long>>);
+static_assert(std::is_same_v<in_out_result<int, long>, partial_sort_copy_result<int, long>>);
 // static_assert(std::is_same_v<in_out_result<int, long>, remove_copy_result<int, long>>);
 // static_assert(std::is_same_v<in_out_result<int, long>, remove_copy_if_result<int, long>>);
 // static_assert(std::is_same_v<in_out_result<int, long>, replace_copy_result<int, long>>);
 // static_assert(std::is_same_v<in_out_result<int, long>, replace_copy_if_result<int, long>>);
 // static_assert(std::is_same_v<in_out_result<int, long>, reverse_copy_result<int, long>>);
 // static_assert(std::is_same_v<in_out_result<int, long>, rotate_copy_result<int, long>>);
 static_assert(std::is_same_v<in_out_result<int, long>, set_difference_result<int, long>>);
 static_assert(std::is_same_v<in_out_result<int, long>, unary_transform_result<int, long>>);

libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
constexpr bool test_all() {
   //using std::ranges::copy_backward_result;
   using std::ranges::copy_if_result;
   using std::ranges::for_each_result;
   using std::ranges::merge_result;
   using std::ranges::minmax_result;
   using std::ranges::mismatch_result;
   using std::ranges::move_result;
   //using std::ranges::move_backward_result;
-  //using std::ranges::partial_sort_copy_result;
+  using std::ranges::partial_sort_copy_result;
   using std::ranges::partition_copy_result;
   //using std::ranges::remove_copy_result;
   //using std::ranges::remove_copy_if_result;
   using std::ranges::reverse_copy_result;
   using std::ranges::rotate_copy_result;
   using std::ranges::set_difference_result;
   using std::ranges::set_intersection_result;
   using std::ranges::set_symmetric_difference_result;
constexpr bool test_all() {
   //dangling_1st(std::ranges::replace_copy_if, in, out, x, x);
   dangling_1st<swap_ranges_result<dangling, int*>>(std::ranges::swap_ranges, in, in2);
   dangling_2nd<swap_ranges_result<int*, dangling>>(std::ranges::swap_ranges, in, in2);
   dangling_both<swap_ranges_result<dangling, dangling>>(std::ranges::swap_ranges, in, in2);
   dangling_1st<reverse_copy_result<dangling, int*>>(std::ranges::reverse_copy, in, out);
   dangling_1st<rotate_copy_result<dangling, int*>>(std::ranges::rotate_copy, in, mid, out);
   //dangling_1st<unique_copy_result<dangling, int*>>(std::ranges::unique_copy, in, out);
   dangling_1st<partition_copy_result<dangling, int*, int*>>(std::ranges::partition_copy, in, out, out2, unary_pred);
-  //dangling_1st<partial_sort_copy_result<dangling, int*>>(std::ranges::partial_sort_copy, in, in2);
-  //dangling_2nd<partial_sort_copy_result<int*, dangling>>(std::ranges::partial_sort_copy, in, in2);
-  //dangling_both<partial_sort_copy_result<dangling, dangling>>(std::ranges::partial_sort_copy, in, in2);
+  dangling_1st<partial_sort_copy_result<dangling, int*>>(std::ranges::partial_sort_copy, in, in2);
+  dangling_2nd<partial_sort_copy_result<int*, dangling>>(std::ranges::partial_sort_copy, in, in2);
+  dangling_both<partial_sort_copy_result<dangling, dangling>>(std::ranges::partial_sort_copy, in, in2);
   dangling_1st<merge_result<dangling, int*, int*>>(std::ranges::merge, in, in2, out);
   dangling_2nd<merge_result<int*, dangling, int*>>(std::ranges::merge, in, in2, out);
   dangling_both<merge_result<dangling, dangling, int*>>(std::ranges::merge, in, in2, out);
   dangling_1st<set_difference_result<dangling, int*>>(std::ranges::set_difference, in, in2, out);
   dangling_1st<set_intersection_result<dangling, int*, int*>>(std::ranges::set_intersection, in, in2, out);
   dangling_2nd<set_intersection_result<int*, dangling, int*>>(std::ranges::set_intersection, in, in2, out);
   dangling_both<set_intersection_result<dangling, dangling, int*>>(std::ranges::set_intersection, in, in2, out);
   dangling_1st<set_symmetric_difference_result<dangling, int*, int*>>(

libcxx/test/std/algorithms/ranges_robust_against_differing_projections.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
constexpr bool test_all() {
   //test(std::ranges::is_permutation, in, in2, eq, proj1, proj2);
   test(std::ranges::includes, in, in2, less, proj1, proj2);
   test(std::ranges::find_first_of, in, in2, eq, proj1, proj2);
   test(std::ranges::mismatch, in, in2, eq, proj1, proj2);
   test(std::ranges::search, in, in2, eq, proj1, proj2);
   test(std::ranges::find_end, in, in2, eq, proj1, proj2);
   test(std::ranges::transform, in, in2, out, sum, proj1, proj2);
   test(std::ranges::transform, in, in2, out2, sum, proj1, proj2);
-  //test(std::ranges::partial_sort_copy, in, in2, output2.begin(), output2.end(), less, proj1, proj2);
+  test(std::ranges::partial_sort_copy, in, in2, less, proj1, proj2);
   test(std::ranges::merge, in, in2, out, less, proj1, proj2);
   test(std::ranges::merge, in, in2, out2, less, proj1, proj2);
   test(std::ranges::set_intersection, in, in2, out, less, proj1, proj2);
   test(std::ranges::set_intersection, in, in2, out2, less, proj1, proj2);
   test(std::ranges::set_difference, in, in2, out, less, proj1, proj2);
   test(std::ranges::set_difference, in, in2, out2, less, proj1, proj2);
   test(std::ranges::set_symmetric_difference, in, in2, out, less, proj1, proj2);
   test(std::ranges::set_symmetric_difference, in, in2, out2, less, proj1, proj2);
   test(std::ranges::set_union, in, in2, out, less, proj1, proj2);
   test(std::ranges::set_union, in, in2, out2, less, proj1, proj2);
+  //test(std::ranges::starts_with, in, in2, eq, proj1, proj2);
+  //test(std::ranges::ends_with, in, in2, eq, proj1, proj2);
 
   return true;
 }
 
 int main(int, char**) {
   test_all();
   static_assert(test_all());
 
   return 0;
 }

libcxx/test/std/algorithms/ranges_robust_against_nonbool_predicates.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
constexpr bool test_all() {
   //std::ranges::clamp(2, 1, 3, binary_pred);
   //test(std::ranges::is_permutation, in, in2, binary_pred);
   test(std::ranges::copy_if, in, out, unary_pred);
   //test(std::ranges::remove_copy_if, in, out, unary_pred);
   test(std::ranges::replace_if, in, unary_pred, x);
   //test(std::ranges::replace_copy_if, in, out, unary_pred, x);
   //test(std::ranges::unique_copy, in, out, binary_pred);
   test(std::ranges::partition_copy, in, out, out2, unary_pred);
-  //test(std::ranges::partial_sort_copy, in, in2, binary_pred);
+  test(std::ranges::partial_sort_copy, in, in2, binary_pred);
   test(std::ranges::merge, in, in2, out, binary_pred);
   test(std::ranges::set_difference, in, in2, out, binary_pred);
   test(std::ranges::set_intersection, in, in2, out, binary_pred);
   test(std::ranges::set_symmetric_difference, in, in2, out, binary_pred);
   test(std::ranges::set_union, in, in2, out, binary_pred);
   test(std::ranges::remove_if, in, unary_pred);
   //test(std::ranges::unique, in, binary_pred);
   test(std::ranges::partition, in, unary_pred);

libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
constexpr bool test_all() {
   //test(std::ranges::replace_copy, in, out, x, a, &Bar::val);
   //test(std::ranges::replace_copy_if, in, out, pred, a, &Bar::val);
   // `swap_ranges` has neither a projection nor a predicate.
   // `reverse_copy` has neither a projection nor a predicate.
   // `rotate_copy` has neither a projection nor a predicate.
   // `sample` has no requirement that the given generator be invoked via `std::invoke`.
   //test(std::ranges::unique_copy, in, out, &Foo::binary_pred, &Bar::val);
   test(std::ranges::partition_copy, in, out, out2, &Foo::unary_pred, &Bar::val);
-  //test(std::ranges::partial_sort_copy, in, in2, &Foo::binary_pred, &Bar::val);
+  test(std::ranges::partial_sort_copy, in, in2, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::merge, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::set_difference, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::set_intersection, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::set_symmetric_difference, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::set_union, in, in2, out, &Foo::binary_pred, &Bar::val, &Bar::val);
   test(std::ranges::remove, in, x, &Bar::val);
   test(std::ranges::remove_if, in, &Foo::unary_pred, &Bar::val);
   // `reverse` has neither a projection nor a predicate.

libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
//test(std::ranges::remove_copy_if, in, out, unary_pred);
     //test(std::ranges::replace_copy_if, in, out, unary_pred, x);
   }
   test(std::ranges::swap_ranges, in, in2);
   if constexpr (std::copyable<T>) {
     test(std::ranges::reverse_copy, in, out);
     test_mid(std::ranges::rotate_copy, in, mid, out);
     //test(std::ranges::unique_copy, in, out);
     test(std::ranges::partition_copy, in, out, out2, unary_pred);
-    //test_mid(std::ranges::partial_sort_copy, in, in2);
+    test(std::ranges::partial_sort_copy, in, in2);
     test(std::ranges::merge, in, in2, out);
     test(std::ranges::set_difference, in, in2, out);
     test(std::ranges::set_intersection, in, in2, out);
     test(std::ranges::set_symmetric_difference, in, in2, out);
     test(std::ranges::set_union, in, in2, out);
   }
   test(std::ranges::remove, in, x);
   test(std::ranges::remove_if, in, unary_pred);

libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 

 static_assert(test(std::ranges::minmax_element, a));
 static_assert(test(std::ranges::mismatch, a, a));
 static_assert(test(std::ranges::move, a, a));
 static_assert(test(std::ranges::move_backward, a, a));
 //static_assert(test(std::ranges::next_permutation, a));
 static_assert(test(std::ranges::none_of, a, odd));
 static_assert(test(std::ranges::nth_element, a, a+5));
 static_assert(test(std::ranges::partial_sort, a, a+5));
-//static_assert(test(std::ranges::partial_sort_copy, a, a));
+static_assert(test(std::ranges::partial_sort_copy, a, a));
 static_assert(test(std::ranges::partition, a, odd));
 static_assert(test(std::ranges::partition_copy, a, a, a, odd));
 static_assert(test(std::ranges::partition_point, a, odd));
 static_assert(test(std::ranges::pop_heap, a));
 //static_assert(test(std::ranges::prev_permutation, a));
 static_assert(test(std::ranges::push_heap, a));
 static_assert(test(std::ranges::remove, a, 42));
 //static_assert(test(std::ranges::remove_copy, a, a, 42));