[libc++] Implement ranges::shift_right (#177847)

Implement the `ranges::shift_right` algorithm from [P2440R1](https://wg21.link/P2440R1). Fixes #134062 Fixes #105184
2026-02-14 17:34:44 +00:00 · 2026-02-14 17:34:44 +00:00 · d7a24d30f6
commit d7a24d30f6
parent 02aa032f6f
18 changed files with 501 additions and 40 deletions
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@ -394,6 +394,8 @@ Status
    ---------------------------------------------------------- -----------------
    ``__cpp_lib_reference_from_temporary``                     *unimplemented*
    ---------------------------------------------------------- -----------------
+    ``__cpp_lib_shift``                                        ``202202L``
+    ---------------------------------------------------------- -----------------
    ``__cpp_lib_spanstream``                                   *unimplemented*
    ---------------------------------------------------------- -----------------
    ``__cpp_lib_stacktrace``                                   *unimplemented*
--- a/libcxx/docs/ReleaseNotes/23.rst
+++ b/libcxx/docs/ReleaseNotes/23.rst
@ -38,7 +38,7 @@ What's New in Libc++ 23.0.0?
 Implemented Papers
 ------------------

- P2440R1 (partial): ``ranges::iota`` and ``ranges::shift_left`` are supported (`Github <https://llvm.org/PR105184>`__)
+- P2440R1: ``ranges::iota``, ``ranges::shift_left`` and ``ranges::shift_right`` (`Github <https://llvm.org/PR105184>`__)

 Improvements and New Features
 -----------------------------
--- a/libcxx/docs/Status/Cxx23Papers.csv
+++ b/libcxx/docs/Status/Cxx23Papers.csv
@ -46,7 +46,7 @@
 "`P2255R2 <https://wg21.link/P2255R2>`__","A type trait to detect reference binding to temporary","2022-02 (Virtual)","|Partial|","","`#105180 <https://github.com/llvm/llvm-project/issues/105180>`__","Implemented the type traits only."
 "`P2273R3 <https://wg21.link/P2273R3>`__","Making ``std::unique_ptr`` constexpr","2022-02 (Virtual)","|Complete|","16","`#105182 <https://github.com/llvm/llvm-project/issues/105182>`__",""
 "`P2387R3 <https://wg21.link/P2387R3>`__","Pipe support for user-defined range adaptors","2022-02 (Virtual)","|Complete|","19","`#105183 <https://github.com/llvm/llvm-project/issues/105183>`__",""
-"`P2440R1 <https://wg21.link/P2440R1>`__","``ranges::iota``, ``ranges::shift_left`` and ``ranges::shift_right``","2022-02 (Virtual)","|Partial|","","`#105184 <https://github.com/llvm/llvm-project/issues/105184>`__","``ranges::iota`` and ``ranges::shift_left`` are implemented."
+"`P2440R1 <https://wg21.link/P2440R1>`__","``ranges::iota``, ``ranges::shift_left`` and ``ranges::shift_right``","2022-02 (Virtual)","|Complete|","23","`#105184 <https://github.com/llvm/llvm-project/issues/105184>`__",""
 "`P2441R2 <https://wg21.link/P2441R2>`__","``views::join_with``","2022-02 (Virtual)","|Complete|","21","`#105185 <https://github.com/llvm/llvm-project/issues/105185>`__",""
 "`P2442R1 <https://wg21.link/P2442R1>`__","Windowing range adaptors: ``views::chunk`` and ``views::slide``","2022-02 (Virtual)","","","`#105187 <https://github.com/llvm/llvm-project/issues/105187>`__",""
 "`P2443R1 <https://wg21.link/P2443R1>`__","``views::chunk_by``","2022-02 (Virtual)","|Complete|","18","`#105188 <https://github.com/llvm/llvm-project/issues/105188>`__",""
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@ -158,6 +158,7 @@ set(files
  __algorithm/ranges_set_symmetric_difference.h
  __algorithm/ranges_set_union.h
  __algorithm/ranges_shift_left.h
+  __algorithm/ranges_shift_right.h
  __algorithm/ranges_shuffle.h
  __algorithm/ranges_sort.h
  __algorithm/ranges_sort_heap.h
--- a/libcxx/include/__algorithm/ranges_shift_right.h
+++ b/libcxx/include/__algorithm/ranges_shift_right.h
@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_SHIFT_RIGHT_H
+#define _LIBCPP___ALGORITHM_RANGES_SHIFT_RIGHT_H
+
+#include <__algorithm/iterator_operations.h>
+#include <__algorithm/shift_right.h>
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/permutable.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/subrange.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+namespace ranges {
+namespace __shift_right {
+
+struct __fn {
+  template <permutable _Iter, sentinel_for<_Iter> _Sent>
+  _LIBCPP_HIDE_FROM_ABI static constexpr subrange<_Iter>
+  operator()(_Iter __first, _Sent __last, iter_difference_t<_Iter> __n) {
+    auto __ret = std::__shift_right<_RangeAlgPolicy>(std::move(__first), std::move(__last), std::move(__n));
+    return {std::move(__ret.first), std::move(__ret.second)};
+  }
+
+  template <forward_range _Range>
+    requires permutable<iterator_t<_Range>>
+  _LIBCPP_HIDE_FROM_ABI static constexpr borrowed_subrange_t<_Range>
+  operator()(_Range&& __range, range_difference_t<_Range> __n) {
+    if constexpr (sized_range<_Range>) {
+      if (__n >= ranges::distance(__range)) {
+        auto __iter = ranges::begin(__range);
+        auto __end  = ranges::end(__range);
+        ranges::advance(__iter, __end);
+        return {__iter, std::move(__iter)};
+      }
+    }
+
+    auto __ret = std::__shift_right<_RangeAlgPolicy>(ranges::begin(__range), ranges::end(__range), std::move(__n));
+    return {std::move(__ret.first), std::move(__ret.second)};
+  }
+};
+} // namespace __shift_right
+
+inline namespace __cpo {
+inline constexpr auto shift_right = __shift_right::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+#endif // _LIBCPP_STD_VER >= 23
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ALGORITHM_RANGES_SHIFT_RIGHT_H
--- a/libcxx/include/__algorithm/shift_right.h
+++ b/libcxx/include/__algorithm/shift_right.h
@ -9,11 +9,17 @@
 #ifndef _LIBCPP___ALGORITHM_SHIFT_RIGHT_H
 #define _LIBCPP___ALGORITHM_SHIFT_RIGHT_H

+#include <__algorithm/iterator_operations.h>
 #include <__algorithm/move.h>
 #include <__algorithm/move_backward.h>
 #include <__algorithm/swap_ranges.h>
+#include <__assert>
+#include <__concepts/derived_from.h>
 #include <__config>
+#include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
+#include <__utility/move.h>
+#include <__utility/pair.h>
 #include <__utility/swap.h>

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@ -27,36 +33,48 @@ _LIBCPP_BEGIN_NAMESPACE_STD

 #if _LIBCPP_STD_VER >= 20

-template <class _ForwardIterator>
-inline _LIBCPP_HIDE_FROM_ABI constexpr _ForwardIterator
-shift_right(_ForwardIterator __first,
-            _ForwardIterator __last,
-            typename iterator_traits<_ForwardIterator>::difference_type __n) {
+template <class _AlgPolicy, class _Iter, class _Sent>
+_LIBCPP_HIDE_FROM_ABI constexpr pair<_Iter, _Iter>
+__shift_right(_Iter __first, _Sent __last, typename _IterOps<_AlgPolicy>::template __difference_type<_Iter> __n) {
+  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__n >= 0, "Providing a negative shift amount to shift_right is UB");
  if (__n == 0) {
-    return __first;
+    _Iter __end = _IterOps<_AlgPolicy>::next(__first, __last);
+    return pair<_Iter, _Iter>(std::move(__first), std::move(__end));
  }

-  if constexpr (__has_random_access_iterator_category<_ForwardIterator>::value) {
-    decltype(__n) __d = __last - __first;
-    if (__n >= __d) {
-      return __last;
+  using _IterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_Iter>;
+
+  if constexpr (derived_from<_IterCategory, random_access_iterator_tag>) {
+    _Iter __end = _IterOps<_AlgPolicy>::next(__first, __last);
+    auto __size = __end - __first;
+    if (__n >= __size) {
+      return pair<_Iter, _Iter>(__end, std::move(__end));
    }
-    _ForwardIterator __m = __first + (__d - __n);
-    return std::move_backward(__first, __m, __last);
-  } else if constexpr (__has_bidirectional_iterator_category<_ForwardIterator>::value) {
-    _ForwardIterator __m = __last;
+    _Iter __m = __first;
+    _IterOps<_AlgPolicy>::advance(__m, (__size - __n));
+    auto __ret = std::__move_backward<_AlgPolicy>(std::move(__first), std::move(__m), __end);
+    return pair<_Iter, _Iter>(std::move(__ret.second), std::move(__end));
+  } else if constexpr (derived_from<_IterCategory, bidirectional_iterator_tag>) {
+    _Iter __end = _IterOps<_AlgPolicy>::next(__first, __last);
+    if constexpr (sized_sentinel_for<_Sent, _Iter>) {
+      if (__n >= ranges::distance(__first, __last)) {
+        return pair<_Iter, _Iter>(__end, std::move(__end));
+      }
+    }
+    _Iter __m = __end;
    for (; __n > 0; --__n) {
      if (__m == __first) {
-        return __last;
+        return pair<_Iter, _Iter>(__end, std::move(__end));
      }
      --__m;
    }
-    return std::move_backward(__first, __m, __last);
+    auto __ret = std::__move_backward<_AlgPolicy>(std::move(__first), std::move(__m), __end);
+    return pair<_Iter, _Iter>(std::move(__ret.second), std::move(__end));
  } else {
-    _ForwardIterator __ret = __first;
+    _Iter __ret = __first;
    for (; __n > 0; --__n) {
      if (__ret == __last) {
-        return __last;
+        return pair<_Iter, _Iter>(__ret, std::move(__ret));
      }
      ++__ret;
    }
@ -64,28 +82,28 @@ shift_right(_ForwardIterator __first,
    // We have an __n-element scratch space from __first to __ret.
    // Slide an __n-element window [__trail, __lead) from left to right.
    // We're essentially doing swap_ranges(__first, __ret, __trail, __lead)
-    // over and over; but once __lead reaches __last we needn't bother
-    // to save the values of elements [__trail, __last).
+    // over and over; but once __lead reaches __end we needn't bother
+    // to save the values of elements [__trail, __end).

    auto __trail = __first;
    auto __lead  = __ret;
    while (__trail != __ret) {
      if (__lead == __last) {
-        std::move(__first, __trail, __ret);
-        return __ret;
+        std::__move<_AlgPolicy>(std::move(__first), std::move(__trail), __ret);
+        return pair<_Iter, _Iter>(__ret, std::move(__lead));
      }
      ++__trail;
      ++__lead;
    }

-    _ForwardIterator __mid = __first;
+    _Iter __mid = __first;
    while (true) {
      if (__lead == __last) {
-        __trail = std::move(__mid, __ret, __trail);
-        std::move(__first, __mid, __trail);
-        return __ret;
+        __trail = std::__move<_AlgPolicy>(__mid, __ret, __trail).second;
+        std::__move<_AlgPolicy>(std::move(__first), std::move(__mid), std::move(__trail));
+        return pair<_Iter, _Iter>(__ret, std::move(__lead));
      }
-      swap(*__mid, *__trail);
+      _IterOps<_AlgPolicy>::iter_swap(__mid, __trail);
      ++__mid;
      ++__trail;
      ++__lead;
@ -96,6 +114,14 @@ shift_right(_ForwardIterator __first,
  }
 }

+template <class _ForwardIterator>
+_LIBCPP_HIDE_FROM_ABI constexpr _ForwardIterator
+shift_right(_ForwardIterator __first,
+            _ForwardIterator __last,
+            typename iterator_traits<_ForwardIterator>::difference_type __n) {
+  return std::__shift_right<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __n).first;
+}
+
 #endif // _LIBCPP_STD_VER >= 20

 _LIBCPP_END_NAMESPACE_STD
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@ -1496,6 +1496,13 @@ template<class ForwardIterator>
    shift_right(ForwardIterator first, ForwardIterator last,
                typename iterator_traits<ForwardIterator>::difference_type n); // C++20

+  template<permutable I, sentinel_for<I> S>
+    constexpr subrange<I> ranges::shift_right(I first, S last, iter_difference_t<I> n);              // since C++23
+
+  template<forward_range R>
+    requires permutable<iterator_t<R>>
+    constexpr borrowed_subrange_t<R> ranges::shift_right(R&& r, range_difference_t<R> n)             // since C++23
+
 template <class InputIterator, class Predicate>
    constexpr bool  // constexpr since C++20
    is_partitioned(InputIterator first, InputIterator last, Predicate pred);
@ -2043,6 +2050,7 @@ template <class BidirectionalIterator, class Compare>
 #    include <__algorithm/ranges_find_last.h>
 #    include <__algorithm/ranges_fold.h>
 #    include <__algorithm/ranges_shift_left.h>
+#    include <__algorithm/ranges_shift_right.h>
 #    include <__algorithm/ranges_starts_with.h>
 #  endif // _LIBCPP_STD_VER >= 23

--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@ -764,6 +764,9 @@ module std [system] {
    module ranges_shift_left {
      header "__algorithm/ranges_shift_left.h"
    }
+    module ranges_shift_right {
+      header "__algorithm/ranges_shift_right.h"
+    }
    module ranges_shuffle {
      header "__algorithm/ranges_shuffle.h"
    }
--- a/libcxx/include/version
+++ b/libcxx/include/version
@ -236,7 +236,8 @@ __cpp_lib_shared_ptr_arrays                             201707L <memory>
                                                        201611L // C++17
 __cpp_lib_shared_ptr_weak_type                          201606L <memory>
 __cpp_lib_shared_timed_mutex                            201402L <shared_mutex>
-__cpp_lib_shift                                         201806L <algorithm>
+__cpp_lib_shift                                         202202L <algorithm>
+                                                        201806L // C++20
 __cpp_lib_smart_ptr_for_overwrite                       202002L <memory>
 __cpp_lib_smart_ptr_owner_equality                      202306L <memory>
 __cpp_lib_source_location                               201907L <source_location>
@ -533,6 +534,8 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # define __cpp_lib_ranges_to_container                  202202L
 # define __cpp_lib_ranges_zip                           202110L
 // # define __cpp_lib_reference_from_temporary             202202L
+# undef  __cpp_lib_shift
+# define __cpp_lib_shift                                202202L
 // # define __cpp_lib_spanstream                           202106L
 // # define __cpp_lib_stacktrace                           202011L
 # define __cpp_lib_stdatomic_h                          202011L
--- a/libcxx/modules/std/algorithm.inc
+++ b/libcxx/modules/std/algorithm.inc
@ -364,9 +364,11 @@ export namespace std {

  using std::shift_right;

+#if _LIBCPP_STD_VER >= 23
  namespace ranges {
-    // using std::ranges::shift_right;
+    using std::ranges::shift_right;
  }
+#endif // _LIBCPP_STD_VER >= 23

  // [alg.sorting], sorting and related operations
  // [alg.sort], sorting
--- a/libcxx/test/libcxx/algorithms/alg.modifying.operations/alg.shift/assert.shift_right.pass.cpp
+++ b/libcxx/test/libcxx/algorithms/alg.modifying.operations/alg.shift/assert.shift_right.pass.cpp
@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// REQUIRES: has-unix-headers
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: libcpp-hardening-mode=none
+// XFAIL: libcpp-hardening-mode=debug && availability-verbose_abort-missing
+
+#include <algorithm>
+#include <array>
+
+#include "check_assertion.h"
+
+int main(int, char**) {
+  std::array<int, 5> arr = {1, 2, 3, 4, 5};
+  TEST_LIBCPP_ASSERT_FAILURE(
+      std::ranges::shift_right(arr, -2), "Providing a negative shift amount to shift_right is UB");
+  TEST_LIBCPP_ASSERT_FAILURE(
+      std::ranges::shift_right(arr.begin(), arr.end(), -2), "Providing a negative shift amount to shift_right is UB");
+
+  return 0;
+}
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.shift/ranges_shift_right.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.shift/ranges_shift_right.pass.cpp
@ -0,0 +1,307 @@
+//===----------------------------------------------------------------------===//
+//
+// 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, c++20
+// ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-steps): -fconstexpr-steps=9000000
+
+// <algorithm>
+
+// template<permutable I, sentinel_for<I> S>
+//   constexpr subrange<I> ranges::shift_right(I first, S last, iter_difference_t<I> n);
+
+// template<forward_range R>
+//   requires permutable<iterator_t<R>>
+//   constexpr borrowed_subrange_t<R> ranges::shift_right(R&& r, range_difference_t<R> n)
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <ranges>
+#include <vector>
+
+#include "almost_satisfies_types.h"
+#include "test_macros.h"
+#include "test_iterators.h"
+#include "MoveOnly.h"
+
+struct InvalidDifferenceT {};
+
+template <class Iter, class Sent = Iter, class N = std::iter_difference_t<Iter>>
+concept HasShiftRightIt = requires(Iter iter, Sent sent, N n) { std::ranges::shift_right(iter, sent, n); };
+
+static_assert(HasShiftRightIt<int*>);
+static_assert(HasShiftRightIt<int*, sentinel_wrapper<int*>>);
+static_assert(HasShiftRightIt<int*, sized_sentinel<int*>>);
+static_assert(!HasShiftRightIt<int*, int*, InvalidDifferenceT>);
+static_assert(!HasShiftRightIt<int*, int, int>);
+
+static_assert(!HasShiftRightIt<ForwardIteratorNotDerivedFrom>);
+static_assert(!HasShiftRightIt<PermutableNotForwardIterator>);
+static_assert(!HasShiftRightIt<PermutableNotSwappable>);
+
+template <class Range, class N = std::ranges::range_difference_t<Range>>
+concept HasShiftRightR = requires(Range range, N n) { std::ranges::shift_right(range, n); };
+
+static_assert(HasShiftRightR<UncheckedRange<int*>>);
+static_assert(!HasShiftRightR<UncheckedRange<int*>, InvalidDifferenceT>);
+
+static_assert(!HasShiftRightR<ForwardRangeNotDerivedFrom>);
+static_assert(!HasShiftRightR<PermutableRangeNotForwardIterator>);
+static_assert(!HasShiftRightR<PermutableRangeNotSwappable>);
+
+struct TrackCopyMove {
+  mutable int copy_count = 0;
+  int move_count         = 0;
+
+  constexpr TrackCopyMove() = default;
+  constexpr TrackCopyMove(const TrackCopyMove& other) : copy_count(other.copy_count), move_count(other.move_count) {
+    ++copy_count;
+    ++other.copy_count;
+  }
+
+  constexpr TrackCopyMove(TrackCopyMove&& other) noexcept : copy_count(other.copy_count), move_count(other.move_count) {
+    ++move_count;
+    ++other.move_count;
+  }
+  constexpr TrackCopyMove& operator=(const TrackCopyMove& other) {
+    ++copy_count;
+    ++other.copy_count;
+    return *this;
+  }
+  constexpr TrackCopyMove& operator=(TrackCopyMove&& other) noexcept {
+    ++move_count;
+    ++other.move_count;
+    return *this;
+  }
+};
+
+template <class Iter, class Sent>
+constexpr void test_iter_sent() {
+  {
+    const std::array<int, 8> original = {3, 1, 4, 1, 5, 9, 2, 6};
+
+    // (iterator, sentinel) overload
+    for (size_t n = 0; n <= original.size(); ++n) {
+      for (size_t k = 0; k <= n + 2; ++k) {
+        std::vector<int> scratch(n);
+        auto begin = Iter(scratch.data());
+        auto end   = Sent(Iter(scratch.data() + n));
+        std::ranges::copy(original.begin(), original.begin() + n, begin);
+        std::same_as<std::ranges::subrange<Iter>> decltype(auto) result = std::ranges::shift_right(begin, end, k);
+
+        assert(result.end() == end);
+        if (k < n) {
+          assert(result.begin() == Iter(scratch.data() + k));
+          assert(std::ranges::equal(original.begin(), original.begin() + n - k, result.begin(), result.end()));
+        } else {
+          assert(result.begin() == end);
+          assert(std::ranges::equal(original.begin(), original.begin() + n, begin, end));
+        }
+      }
+    }
+
+    // (range) overload
+    for (size_t n = 0; n <= original.size(); ++n) {
+      for (size_t k = 0; k <= n + 2; ++k) {
+        std::vector<int> scratch(n);
+        auto begin = Iter(scratch.data());
+        auto end   = Sent(Iter(scratch.data() + n));
+        std::ranges::copy(original.begin(), original.begin() + n, begin);
+        auto range                                                      = std::ranges::subrange(begin, end);
+        std::same_as<std::ranges::subrange<Iter>> decltype(auto) result = std::ranges::shift_right(range, k);
+
+        assert(result.end() == end);
+        if (k < n) {
+          assert(result.begin() == Iter(scratch.data() + k));
+          assert(std::ranges::equal(original.begin(), original.begin() + n - k, result.begin(), result.end()));
+        } else {
+          assert(result.begin() == end);
+          assert(std::ranges::equal(original.begin(), original.begin() + n, begin, end));
+        }
+      }
+    }
+  }
+  // n == 0
+  {
+    std::array<int, 3> input          = {0, 1, 2};
+    const std::array<int, 3> expected = {0, 1, 2};
+
+    { // (iterator, sentinel) overload
+      auto in                                                         = input;
+      auto begin                                                      = Iter(in.data());
+      auto end                                                        = Sent(Iter(in.data() + in.size()));
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result = std::ranges::shift_right(begin, end, 0);
+      assert(std::ranges::equal(expected, result));
+      assert(result.begin() == begin);
+      assert(result.end() == end);
+    }
+
+    { // (range) overload
+      auto in                                                         = input;
+      auto begin                                                      = Iter(in.data());
+      auto end                                                        = Sent(Iter(in.data() + in.size()));
+      auto range                                                      = std::ranges::subrange(begin, end);
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result = std::ranges::shift_right(range, 0);
+      assert(std::ranges::equal(expected, result));
+      assert(result.begin() == begin);
+      assert(result.end() == end);
+    }
+  }
+
+  // n == len
+  {
+    std::array<int, 3> input          = {0, 1, 2};
+    const std::array<int, 3> expected = {0, 1, 2};
+
+    { // (iterator, sentinel) overload
+      auto in    = input;
+      auto begin = Iter(in.data());
+      auto end   = Sent(Iter(in.data() + in.size()));
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result =
+          std::ranges::shift_right(begin, end, input.size());
+      assert(std::ranges::equal(expected, input));
+      assert(result.begin() == end);
+      assert(result.end() == end);
+    }
+
+    { // (range) overload
+      auto in                                                         = input;
+      auto begin                                                      = Iter(in.data());
+      auto end                                                        = Sent(Iter(in.data() + in.size()));
+      auto range                                                      = std::ranges::subrange(begin, end);
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result = std::ranges::shift_right(range, input.size());
+      assert(std::ranges::equal(expected, input));
+      assert(result.begin() == end);
+      assert(result.end() == end);
+    }
+  }
+
+  // n > len
+  {
+    std::array<int, 3> input          = {0, 1, 2};
+    const std::array<int, 3> expected = {0, 1, 2};
+
+    { // (iterator, sentinel) overload
+      auto in    = input;
+      auto begin = Iter(in.data());
+      auto end   = Sent(Iter(in.data() + in.size()));
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result =
+          std::ranges::shift_right(begin, end, input.size() + 1);
+      assert(std::ranges::equal(expected, input));
+      assert(result.begin() == end);
+      assert(result.end() == end);
+    }
+
+    { // (range) overload
+      auto in    = input;
+      auto begin = Iter(in.data());
+      auto end   = Sent(Iter(in.data() + in.size()));
+      auto range = std::ranges::subrange(begin, end);
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result =
+          std::ranges::shift_right(range, input.size() + 1);
+      assert(std::ranges::equal(expected, input));
+      assert(result.begin() == end);
+      assert(result.end() == end);
+    }
+  }
+
+  // empty range
+  {
+    std::vector<int> input          = {};
+    const std::vector<int> expected = {};
+    { // (iterator, sentinel) overload
+      auto in    = input;
+      auto begin = Iter(in.data());
+      auto end   = Sent(Iter(in.data() + in.size()));
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result =
+          std::ranges::shift_right(begin, end, input.size() + 1);
+      assert(std::ranges::equal(expected, input));
+      assert(result.begin() == begin);
+      assert(result.end() == begin);
+    }
+
+    { // (range) overload
+      auto in    = input;
+      auto begin = Iter(in.data());
+      auto end   = Sent(Iter(in.data() + in.size()));
+      auto range = std::ranges::subrange(begin, end);
+      std::same_as<std::ranges::subrange<Iter>> decltype(auto) result =
+          std::ranges::shift_right(range, input.size() + 1);
+      assert(std::ranges::equal(expected, input));
+      assert(result.begin() == begin);
+      assert(result.end() == begin);
+    }
+  }
+}
+
+constexpr bool test() {
+  types::for_each(types::forward_iterator_list<int*>{}, []<class Iter> {
+    test_iter_sent<Iter, Iter>();
+    test_iter_sent<Iter, sentinel_wrapper<Iter>>();
+    test_iter_sent<Iter, sized_sentinel<Iter>>();
+  });
+
+  // Complexity: At most (last - first) - n assignments or swaps.
+  {
+    constexpr int length = 100;
+    constexpr int n      = length / 2;
+    auto make_vec        = []() {
+      std::vector<TrackCopyMove> vec;
+      vec.reserve(length);
+      for (int i = 0; i < length; ++i) {
+        vec.emplace_back();
+      }
+      return vec;
+    };
+
+    { // (iterator, sentinel) overload
+      auto input  = make_vec();
+      auto result = std::ranges::shift_right(input.begin(), input.end(), n);
+      assert(result.begin() == input.begin() + length - n);
+      assert(result.end() == input.end());
+
+      auto total_copies = 0;
+      auto total_moves  = 0;
+      for (auto it = result.begin(); it != result.end(); ++it) {
+        const auto& item = *it;
+        total_copies += item.copy_count;
+        total_moves += item.move_count;
+      }
+
+      assert(total_copies == 0);
+      assert(total_moves <= length - n);
+    }
+
+    { // (range) overload
+      auto input  = make_vec();
+      auto result = std::ranges::shift_right(input, n);
+      assert(result.begin() == input.begin() + length - n);
+      assert(result.end() == input.end());
+
+      auto total_copies = 0;
+      auto total_moves  = 0;
+      for (auto it = result.begin(); it != result.end(); ++it) {
+        const auto& item = *it;
+        total_copies += item.copy_count;
+        total_moves += item.move_count;
+      }
+
+      assert(total_copies == 0);
+      assert(total_moves <= length - n);
+    }
+  }
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}
--- a/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
@ -225,6 +225,7 @@ constexpr bool test_all() {
 #if TEST_STD_VER >= 23
  dangling_1st<out_value_result<dangling, decltype(x)>>(std::ranges::iota, in, x);
  dangling_1st(std::ranges::shift_left, in, x);
+  dangling_1st(std::ranges::shift_right, in, x);
 #endif

  return true;
--- a/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
@ -193,7 +193,9 @@ constexpr void run_tests() {
  test(std::ranges::next_permutation, in);
 #if TEST_STD_VER >= 23
  test(std::ranges::shift_left, in, count);
+  test(std::ranges::shift_right, in, count);
 #endif
+
  // The algorithms that work on uninitialized memory have constraints that prevent proxy iterators from being used with
  // them.
 }
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/algorithm.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/algorithm.version.compile.pass.cpp
@ -348,8 +348,8 @@
 #  ifndef __cpp_lib_shift
 #    error "__cpp_lib_shift should be defined in c++23"
 #  endif
-#  if __cpp_lib_shift != 201806L
-#    error "__cpp_lib_shift should have the value 201806L in c++23"
+#  if __cpp_lib_shift != 202202L
+#    error "__cpp_lib_shift should have the value 202202L in c++23"
 #  endif

 #elif TEST_STD_VER > 23
@ -452,8 +452,8 @@
 #  ifndef __cpp_lib_shift
 #    error "__cpp_lib_shift should be defined in c++26"
 #  endif
-#  if __cpp_lib_shift != 201806L
-#    error "__cpp_lib_shift should have the value 201806L in c++26"
+#  if __cpp_lib_shift != 202202L
+#    error "__cpp_lib_shift should have the value 202202L in c++26"
 #  endif

 #endif // TEST_STD_VER > 23
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
@ -5916,8 +5916,8 @@
 #  ifndef __cpp_lib_shift
 #    error "__cpp_lib_shift should be defined in c++23"
 #  endif
-#  if __cpp_lib_shift != 201806L
-#    error "__cpp_lib_shift should have the value 201806L in c++23"
+#  if __cpp_lib_shift != 202202L
+#    error "__cpp_lib_shift should have the value 202202L in c++23"
 #  endif

 #  ifndef __cpp_lib_smart_ptr_for_overwrite
@ -7868,8 +7868,8 @@
 #  ifndef __cpp_lib_shift
 #    error "__cpp_lib_shift should be defined in c++26"
 #  endif
-#  if __cpp_lib_shift != 201806L
-#    error "__cpp_lib_shift should have the value 201806L in c++26"
+#  if __cpp_lib_shift != 202202L
+#    error "__cpp_lib_shift should have the value 202202L in c++26"
 #  endif

 #  ifndef __cpp_lib_smart_ptr_for_overwrite
--- a/libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp
+++ b/libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp
@ -157,6 +157,7 @@ static_assert(test(std::ranges::set_symmetric_difference, a, a, a));
 static_assert(test(std::ranges::set_union, a, a, a));
 #if TEST_STD_VER >= 23
 static_assert(test(std::ranges::shift_left, a, 42));
+static_assert(test(std::ranges::shift_right, a, 42));
 #endif
 static_assert(test(std::ranges::shuffle, a, g));
 static_assert(test(std::ranges::sort, a));
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@ -1270,7 +1270,7 @@ feature_test_macros = [
        },
        {
            "name": "__cpp_lib_shift",
-            "values": {"c++20": 201806},
+            "values": {"c++20": 201806, "c++23": 202202},
            "headers": ["algorithm"],
        },
        {