[libcxx-commits] [libcxx] [libc++] Merge the private iterator_traits aliases with their ranges versions (PR #162661)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/162661

None

>From 60d4a6332f9f4aeb0295a1779da21e58cd2c0743 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Thu, 9 Oct 2025 15:39:34 +0200
Subject: [PATCH] [libc++] Merge the private iterator_traits aliases with their
 ranges versions

---
 libcxx/include/__algorithm/copy.h             |  3 +-
 libcxx/include/__algorithm/copy_backward.h    |  3 +-
 libcxx/include/__algorithm/count.h            | 15 ++--
 libcxx/include/__algorithm/count_if.h         |  9 +--
 libcxx/include/__algorithm/is_permutation.h   |  8 +-
 .../include/__algorithm/iterator_operations.h | 35 +++------
 .../lexicographical_compare_three_way.h       |  8 +-
 libcxx/include/__algorithm/make_heap.h        |  4 +-
 libcxx/include/__algorithm/mismatch.h         |  2 +-
 libcxx/include/__algorithm/move.h             |  3 +-
 libcxx/include/__algorithm/move_backward.h    |  3 +-
 libcxx/include/__algorithm/pstl.h             |  4 +-
 libcxx/include/__algorithm/radix_sort.h       | 43 +++++------
 libcxx/include/__algorithm/ranges_count.h     |  6 +-
 libcxx/include/__algorithm/ranges_count_if.h  |  4 +-
 .../include/__algorithm/ranges_unique_copy.h  |  4 +-
 libcxx/include/__algorithm/sample.h           |  2 +-
 libcxx/include/__algorithm/sift_down.h        |  4 +-
 libcxx/include/__algorithm/stable_sort.h      |  2 +-
 libcxx/include/__algorithm/unique_copy.h      | 10 +--
 .../strict_weak_ordering_check.h              |  2 +-
 libcxx/include/__flat_set/flat_multiset.h     |  8 +-
 libcxx/include/__flat_set/flat_set.h          |  9 +--
 libcxx/include/__iterator/bounded_iter.h      |  4 +-
 .../__iterator/cpp17_iterator_concepts.h      | 25 +++---
 libcxx/include/__iterator/iterator_traits.h   | 76 +++++++++++--------
 .../include/__iterator/static_bounded_iter.h  |  4 +-
 libcxx/include/__iterator/wrap_iter.h         | 12 +--
 libcxx/include/__numeric/pstl.h               |  4 +-
 libcxx/include/__pstl/backends/default.h      | 28 +++----
 libcxx/include/__pstl/backends/libdispatch.h  |  4 +-
 libcxx/include/__pstl/cpu_algos/find_if.h     |  2 +-
 libcxx/include/__pstl/cpu_algos/transform.h   | 11 +--
 .../__pstl/cpu_algos/transform_reduce.h       |  9 +--
 libcxx/include/__vector/vector.h              |  6 +-
 libcxx/include/deque                          |  6 +-
 libcxx/include/forward_list                   |  6 +-
 libcxx/include/list                           |  6 +-
 libcxx/include/queue                          | 20 +++--
 libcxx/include/set                            | 16 ++--
 libcxx/include/stack                          |  4 +-
 libcxx/include/string                         |  2 +-
 libcxx/include/unordered_set                  | 39 ++++------
 .../cpp17_iterator_concepts.verify.cpp        |  4 +-
 44 files changed, 227 insertions(+), 252 deletions(-)

diff --git a/libcxx/include/__algorithm/copy.h b/libcxx/include/__algorithm/copy.h
index 21fd25ce6fcdc..a4344c0d711cf 100644
--- a/libcxx/include/__algorithm/copy.h
+++ b/libcxx/include/__algorithm/copy.h
@@ -197,8 +197,7 @@ struct __copy_impl {
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
   operator()(_InIter __first, _InIter __last, _OutIter __result) const {
     using _Traits = __segmented_iterator_traits<_OutIter>;
-    using _DiffT =
-        typename common_type<__iterator_difference_type<_InIter>, __iterator_difference_type<_OutIter> >::type;
+    using _DiffT  = typename common_type<__iter_difference_t<_InIter>, __iter_difference_t<_OutIter> >::type;
 
     if (__first == __last)
       return std::make_pair(std::move(__first), std::move(__result));
diff --git a/libcxx/include/__algorithm/copy_backward.h b/libcxx/include/__algorithm/copy_backward.h
index 6c9eba672e154..48a365a1079e8 100644
--- a/libcxx/include/__algorithm/copy_backward.h
+++ b/libcxx/include/__algorithm/copy_backward.h
@@ -214,8 +214,7 @@ struct __copy_backward_impl {
 
     auto __local_last = _Traits::__local(__result);
     while (true) {
-      using _DiffT =
-          typename common_type<__iterator_difference_type<_InIter>, __iterator_difference_type<_OutIter> >::type;
+      using _DiffT = typename common_type<__iter_difference_t<_InIter>, __iter_difference_t<_OutIter> >::type;
 
       auto __local_first = _Traits::__begin(__segment_iterator);
       auto __size        = std::min<_DiffT>(__local_last - __local_first, __last - __first);
diff --git a/libcxx/include/__algorithm/count.h b/libcxx/include/__algorithm/count.h
index 8529d110a30aa..eef77c0055340 100644
--- a/libcxx/include/__algorithm/count.h
+++ b/libcxx/include/__algorithm/count.h
@@ -10,7 +10,6 @@
 #ifndef _LIBCPP___ALGORITHM_COUNT_H
 #define _LIBCPP___ALGORITHM_COUNT_H
 
-#include <__algorithm/iterator_operations.h>
 #include <__algorithm/min.h>
 #include <__bit/invert_if.h>
 #include <__bit/popcount.h>
@@ -31,10 +30,10 @@ _LIBCPP_PUSH_MACROS
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // generic implementation
-template <class _AlgPolicy, class _Iter, class _Sent, class _Tp, class _Proj>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename _IterOps<_AlgPolicy>::template __difference_type<_Iter>
+template <class _Iter, class _Sent, class _Tp, class _Proj>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_difference_t<_Iter>
 __count(_Iter __first, _Sent __last, const _Tp& __value, _Proj& __proj) {
-  typename _IterOps<_AlgPolicy>::template __difference_type<_Iter> __r(0);
+  __iter_difference_t<_Iter> __r(0);
   for (; __first != __last; ++__first)
     if (std::__invoke(__proj, *__first) == __value)
       ++__r;
@@ -71,8 +70,8 @@ __count_bool(__bit_iterator<_Cp, _IsConst> __first, typename __size_difference_t
   return __r;
 }
 
-template <class, class _Cp, bool _IsConst, class _Tp, class _Proj, __enable_if_t<__is_identity<_Proj>::value, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iterator_difference_type<__bit_iterator<_Cp, _IsConst> >
+template <class _Cp, bool _IsConst, class _Tp, class _Proj, __enable_if_t<__is_identity<_Proj>::value, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_difference_t<__bit_iterator<_Cp, _IsConst> >
 __count(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value, _Proj&) {
   if (__value)
     return std::__count_bool<true>(
@@ -82,10 +81,10 @@ __count(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __l
 }
 
 template <class _InputIterator, class _Tp>
-[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iterator_difference_type<_InputIterator>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __iter_difference_t<_InputIterator>
 count(_InputIterator __first, _InputIterator __last, const _Tp& __value) {
   __identity __proj;
-  return std::__count<_ClassicAlgPolicy>(__first, __last, __value, __proj);
+  return std::__count(__first, __last, __value, __proj);
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/count_if.h b/libcxx/include/__algorithm/count_if.h
index 26f945e6bd98c..46fa2e64c9b74 100644
--- a/libcxx/include/__algorithm/count_if.h
+++ b/libcxx/include/__algorithm/count_if.h
@@ -10,7 +10,6 @@
 #ifndef _LIBCPP___ALGORITHM_COUNT_IF_H
 #define _LIBCPP___ALGORITHM_COUNT_IF_H
 
-#include <__algorithm/iterator_operations.h>
 #include <__config>
 #include <__functional/identity.h>
 #include <__iterator/iterator_traits.h>
@@ -22,10 +21,10 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _AlgPolicy, class _Iter, class _Sent, class _Proj, class _Pred>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __policy_iter_diff_t<_AlgPolicy, _Iter>
+template <class _Iter, class _Sent, class _Proj, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __iter_difference_t<_Iter>
 __count_if(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
-  __policy_iter_diff_t<_AlgPolicy, _Iter> __counter(0);
+  __iter_difference_t<_Iter> __counter(0);
   for (; __first != __last; ++__first) {
     if (std::__invoke(__pred, std::__invoke(__proj, *__first)))
       ++__counter;
@@ -38,7 +37,7 @@ template <class _InputIterator, class _Predicate>
 typename iterator_traits<_InputIterator>::difference_type
 count_if(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
   __identity __proj;
-  return std::__count_if<_ClassicAlgPolicy>(__first, __last, __pred, __proj);
+  return std::__count_if(__first, __last, __pred, __proj);
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__algorithm/is_permutation.h b/libcxx/include/__algorithm/is_permutation.h
index 86f469c2799c5..0908001cd1a24 100644
--- a/libcxx/include/__algorithm/is_permutation.h
+++ b/libcxx/include/__algorithm/is_permutation.h
@@ -78,7 +78,7 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation_impl(
     _Pred&& __pred,
     _Proj1&& __proj1,
     _Proj2&& __proj2) {
-  using _D1 = __iterator_difference_type<_Iter1>;
+  using _D1 = __iter_difference_t<_Iter1>;
 
   for (auto __i = __first1; __i != __last1; ++__i) {
     //  Have we already counted the number of *__i in [f1, l1)?
@@ -126,7 +126,7 @@ template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _Fo
     return true;
 
   //  __first1 != __last1 && *__first1 != *__first2
-  using _D1 = __iterator_difference_type<_ForwardIterator1>;
+  using _D1 = __iter_difference_t<_ForwardIterator1>;
   _D1 __l1  = _IterOps<_AlgPolicy>::distance(__first1, __last1);
   if (__l1 == _D1(1))
     return false;
@@ -173,10 +173,10 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation(
   if (__first2 == __last2) // Second range is shorter
     return false;
 
-  using _D1 = __iterator_difference_type<_Iter1>;
+  using _D1 = __iter_difference_t<_Iter1>;
   _D1 __l1  = _IterOps<_AlgPolicy>::distance(__first1, __last1);
 
-  using _D2 = __iterator_difference_type<_Iter2>;
+  using _D2 = __iter_difference_t<_Iter2>;
   _D2 __l2  = _IterOps<_AlgPolicy>::distance(__first2, __last2);
   if (__l1 != __l2)
     return false;
diff --git a/libcxx/include/__algorithm/iterator_operations.h b/libcxx/include/__algorithm/iterator_operations.h
index e5c89c1e67e3a..375ac1db1a1a8 100644
--- a/libcxx/include/__algorithm/iterator_operations.h
+++ b/libcxx/include/__algorithm/iterator_operations.h
@@ -47,15 +47,9 @@ struct _RangeAlgPolicy {};
 
 template <>
 struct _IterOps<_RangeAlgPolicy> {
-  template <class _Iter>
-  using __value_type _LIBCPP_NODEBUG = iter_value_t<_Iter>;
-
   template <class _Iter>
   using __iterator_category _LIBCPP_NODEBUG = ranges::__iterator_concept<_Iter>;
 
-  template <class _Iter>
-  using __difference_type _LIBCPP_NODEBUG = iter_difference_t<_Iter>;
-
   static constexpr auto advance      = ranges::advance;
   static constexpr auto distance     = ranges::distance;
   static constexpr auto __iter_move  = ranges::iter_move;
@@ -71,15 +65,9 @@ struct _ClassicAlgPolicy {};
 
 template <>
 struct _IterOps<_ClassicAlgPolicy> {
-  template <class _Iter>
-  using __value_type _LIBCPP_NODEBUG = typename iterator_traits<_Iter>::value_type;
-
   template <class _Iter>
   using __iterator_category _LIBCPP_NODEBUG = typename iterator_traits<_Iter>::iterator_category;
 
-  template <class _Iter>
-  using __difference_type _LIBCPP_NODEBUG = typename iterator_traits<_Iter>::difference_type;
-
   // advance
   template <class _Iter, class _Distance>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static void advance(_Iter& __iter, _Distance __count) {
@@ -164,17 +152,17 @@ struct _IterOps<_ClassicAlgPolicy> {
 
   // advance with sentinel, a la std::ranges::advance
   template <class _Iter>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __difference_type<_Iter>
-  __advance_to(_Iter& __iter, __difference_type<_Iter> __count, const _Iter& __sentinel) {
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __iter_difference_t<_Iter>
+  __advance_to(_Iter& __iter, __iter_difference_t<_Iter> __count, const _Iter& __sentinel) {
     return _IterOps::__advance_to(__iter, __count, __sentinel, typename iterator_traits<_Iter>::iterator_category());
   }
 
 private:
   // advance with sentinel, a la std::ranges::advance -- InputIterator specialization
   template <class _InputIter>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __difference_type<_InputIter> __advance_to(
-      _InputIter& __iter, __difference_type<_InputIter> __count, const _InputIter& __sentinel, input_iterator_tag) {
-    __difference_type<_InputIter> __dist = 0;
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __iter_difference_t<_InputIter> __advance_to(
+      _InputIter& __iter, __iter_difference_t<_InputIter> __count, const _InputIter& __sentinel, input_iterator_tag) {
+    __iter_difference_t<_InputIter> __dist = 0;
     for (; __dist < __count && __iter != __sentinel; ++__dist)
       ++__iter;
     return __count - __dist;
@@ -182,12 +170,12 @@ struct _IterOps<_ClassicAlgPolicy> {
 
   // advance with sentinel, a la std::ranges::advance -- BidirectionalIterator specialization
   template <class _BiDirIter>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __difference_type<_BiDirIter>
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __iter_difference_t<_BiDirIter>
   __advance_to(_BiDirIter& __iter,
-               __difference_type<_BiDirIter> __count,
+               __iter_difference_t<_BiDirIter> __count,
                const _BiDirIter& __sentinel,
                bidirectional_iterator_tag) {
-    __difference_type<_BiDirIter> __dist = 0;
+    __iter_difference_t<_BiDirIter> __dist = 0;
     if (__count >= 0)
       for (; __dist < __count && __iter != __sentinel; ++__dist)
         ++__iter;
@@ -199,9 +187,9 @@ struct _IterOps<_ClassicAlgPolicy> {
 
   // advance with sentinel, a la std::ranges::advance -- RandomIterator specialization
   template <class _RandIter>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __difference_type<_RandIter>
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 static __iter_difference_t<_RandIter>
   __advance_to(_RandIter& __iter,
-               __difference_type<_RandIter> __count,
+               __iter_difference_t<_RandIter> __count,
                const _RandIter& __sentinel,
                random_access_iterator_tag) {
     auto __dist = _IterOps::distance(__iter, __sentinel);
@@ -216,9 +204,6 @@ struct _IterOps<_ClassicAlgPolicy> {
   }
 };
 
-template <class _AlgPolicy, class _Iter>
-using __policy_iter_diff_t _LIBCPP_NODEBUG = typename _IterOps<_AlgPolicy>::template __difference_type<_Iter>;
-
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
diff --git a/libcxx/include/__algorithm/lexicographical_compare_three_way.h b/libcxx/include/__algorithm/lexicographical_compare_three_way.h
index 442223e79e4ec..a350232af17b2 100644
--- a/libcxx/include/__algorithm/lexicographical_compare_three_way.h
+++ b/libcxx/include/__algorithm/lexicographical_compare_three_way.h
@@ -37,13 +37,13 @@ template <class _InputIterator1, class _InputIterator2, class _Cmp>
 _LIBCPP_HIDE_FROM_ABI constexpr auto __lexicographical_compare_three_way_fast_path(
     _InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2, _Cmp& __comp)
     -> decltype(__comp(*__first1, *__first2)) {
-  static_assert(signed_integral<__iterator_difference_type<_InputIterator1>>,
+  static_assert(signed_integral<__iter_difference_t<_InputIterator1>>,
                 "Using a non-integral difference_type is undefined behavior.");
-  static_assert(signed_integral<__iterator_difference_type<_InputIterator2>>,
+  static_assert(signed_integral<__iter_difference_t<_InputIterator2>>,
                 "Using a non-integral difference_type is undefined behavior.");
 
-  using _Len1   = __iterator_difference_type<_InputIterator1>;
-  using _Len2   = __iterator_difference_type<_InputIterator2>;
+  using _Len1   = __iter_difference_t<_InputIterator1>;
+  using _Len2   = __iter_difference_t<_InputIterator2>;
   using _Common = common_type_t<_Len1, _Len2>;
 
   _Len1 __len1      = __last1 - __first1;
diff --git a/libcxx/include/__algorithm/make_heap.h b/libcxx/include/__algorithm/make_heap.h
index f98a0d2f89c85..0f98d6fd80ae6 100644
--- a/libcxx/include/__algorithm/make_heap.h
+++ b/libcxx/include/__algorithm/make_heap.h
@@ -33,10 +33,10 @@ inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
 __make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare&& __comp) {
   __comp_ref_type<_Compare> __comp_ref = __comp;
 
-  using __diff_t     = __iterator_difference_type<_RandomAccessIterator>;
+  using __diff_t     = __iter_difference_t<_RandomAccessIterator>;
   const __diff_t __n = __last - __first;
 
-  const bool __assume_both_children = is_arithmetic<__iterator_value_type<_RandomAccessIterator> >::value;
+  const bool __assume_both_children = is_arithmetic<__iter_value_t<_RandomAccessIterator> >::value;
 
   // While it would be correct to always assume we have both children, in practice we observed this to be a performance
   // improvement only for arithmetic types.
diff --git a/libcxx/include/__algorithm/mismatch.h b/libcxx/include/__algorithm/mismatch.h
index 749c701974f07..fd1e989467d2e 100644
--- a/libcxx/include/__algorithm/mismatch.h
+++ b/libcxx/include/__algorithm/mismatch.h
@@ -60,7 +60,7 @@ __mismatch(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Pred& __pred, _Pro
 template <class _Iter>
 [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_Iter, _Iter>
 __mismatch_vectorized(_Iter __first1, _Iter __last1, _Iter __first2) {
-  using __value_type              = __iterator_value_type<_Iter>;
+  using __value_type              = __iter_value_t<_Iter>;
   constexpr size_t __unroll_count = 4;
   constexpr size_t __vec_size     = __native_vector_size<__value_type>;
   using __vec                     = __simd_vector<__value_type, __vec_size>;
diff --git a/libcxx/include/__algorithm/move.h b/libcxx/include/__algorithm/move.h
index 52bd5fb5253db..031560c3b1b76 100644
--- a/libcxx/include/__algorithm/move.h
+++ b/libcxx/include/__algorithm/move.h
@@ -80,8 +80,7 @@ struct __move_impl {
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
   operator()(_InIter __first, _InIter __last, _OutIter __result) const {
     using _Traits = __segmented_iterator_traits<_OutIter>;
-    using _DiffT =
-        typename common_type<__iterator_difference_type<_InIter>, __iterator_difference_type<_OutIter> >::type;
+    using _DiffT  = typename common_type<__iter_difference_t<_InIter>, __iter_difference_t<_OutIter> >::type;
 
     if (__first == __last)
       return std::make_pair(std::move(__first), std::move(__result));
diff --git a/libcxx/include/__algorithm/move_backward.h b/libcxx/include/__algorithm/move_backward.h
index a4698327b474d..a6a7130b47719 100644
--- a/libcxx/include/__algorithm/move_backward.h
+++ b/libcxx/include/__algorithm/move_backward.h
@@ -86,8 +86,7 @@ struct __move_backward_impl {
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
   operator()(_InIter __first, _InIter __last, _OutIter __result) const {
     using _Traits = __segmented_iterator_traits<_OutIter>;
-    using _DiffT =
-        typename common_type<__iterator_difference_type<_InIter>, __iterator_difference_type<_OutIter> >::type;
+    using _DiffT  = typename common_type<__iter_difference_t<_InIter>, __iter_difference_t<_OutIter> >::type;
 
     // When the range contains no elements, __result might not be a valid iterator
     if (__first == __last)
diff --git a/libcxx/include/__algorithm/pstl.h b/libcxx/include/__algorithm/pstl.h
index eea07e2b96b64..e0f4e9dac62ea 100644
--- a/libcxx/include/__algorithm/pstl.h
+++ b/libcxx/include/__algorithm/pstl.h
@@ -115,7 +115,7 @@ template <class _ExecutionPolicy,
           class _Predicate,
           class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
           enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI __iterator_difference_type<_ForwardIterator>
+_LIBCPP_HIDE_FROM_ABI __iter_difference_t<_ForwardIterator>
 count_if(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
   _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
       _ForwardIterator, "count_if(first, last, pred) requires [first, last) to be ForwardIterators");
@@ -129,7 +129,7 @@ template <class _ExecutionPolicy,
           class _Tp,
           class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
           enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI __iterator_difference_type<_ForwardIterator>
+_LIBCPP_HIDE_FROM_ABI __iter_difference_t<_ForwardIterator>
 count(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
   _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
       _ForwardIterator, "count(first, last, val) requires [first, last) to be ForwardIterators");
diff --git a/libcxx/include/__algorithm/radix_sort.h b/libcxx/include/__algorithm/radix_sort.h
index 5549a69f5e220..290a36ca3cca0 100644
--- a/libcxx/include/__algorithm/radix_sort.h
+++ b/libcxx/include/__algorithm/radix_sort.h
@@ -72,14 +72,14 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 #if _LIBCPP_STD_VER >= 14
 
 template <class _InputIterator, class _OutputIterator>
-_LIBCPP_HIDE_FROM_ABI constexpr pair<_OutputIterator, __iterator_value_type<_InputIterator>>
+_LIBCPP_HIDE_FROM_ABI constexpr pair<_OutputIterator, __iter_value_t<_InputIterator>>
 __partial_sum_max(_InputIterator __first, _InputIterator __last, _OutputIterator __result) {
   if (__first == __last)
     return {__result, 0};
 
-  auto __max                                  = *__first;
-  __iterator_value_type<_InputIterator> __sum = *__first;
-  *__result                                   = __sum;
+  auto __max                           = *__first;
+  __iter_value_t<_InputIterator> __sum = *__first;
+  *__result                            = __sum;
 
   while (++__first != __last) {
     if (__max < *__first) {
@@ -124,7 +124,7 @@ _LIBCPP_HIDE_FROM_ABI constexpr auto __nth_radix(size_t __radix_number, _Radix _
 template <class _ForwardIterator, class _Map, class _RandomAccessIterator>
 _LIBCPP_HIDE_FROM_ABI constexpr void
 __collect(_ForwardIterator __first, _ForwardIterator __last, _Map __map, _RandomAccessIterator __counters) {
-  using __value_type = __iterator_value_type<_ForwardIterator>;
+  using __value_type = __iter_value_t<_ForwardIterator>;
   using __traits     = __counting_sort_traits<__value_type, _Map>;
 
   std::for_each(__first, __last, [&__counters, &__map](const auto& __preimage) { ++__counters[__map(__preimage)]; });
@@ -160,7 +160,7 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool __collect_impl(
     _RandomAccessIterator1 __counters,
     _RandomAccessIterator2 __maximums,
     index_sequence<_Radices...>) {
-  using __value_type                 = __iterator_value_type<_ForwardIterator>;
+  using __value_type                 = __iter_value_t<_ForwardIterator>;
   constexpr auto __radix_value_range = __radix_sort_traits<__value_type, _Map, _Radix>::__radix_value_range;
 
   auto __previous  = numeric_limits<__invoke_result_t<_Map, __value_type>>::min();
@@ -189,7 +189,7 @@ __collect(_ForwardIterator __first,
           _Radix __radix,
           _RandomAccessIterator1 __counters,
           _RandomAccessIterator2 __maximums) {
-  using __value_type           = __iterator_value_type<_ForwardIterator>;
+  using __value_type           = __iter_value_t<_ForwardIterator>;
   constexpr auto __radix_count = __radix_sort_traits<__value_type, _Map, _Radix>::__radix_count;
   return std::__collect_impl(
       __first, __last, __map, __radix, __counters, __maximums, make_index_sequence<__radix_count>());
@@ -213,10 +213,10 @@ _LIBCPP_HIDE_FROM_ABI constexpr void __dispose_backward(
 template <class _ForwardIterator, class _RandomAccessIterator, class _Map>
 _LIBCPP_HIDE_FROM_ABI constexpr _RandomAccessIterator
 __counting_sort_impl(_ForwardIterator __first, _ForwardIterator __last, _RandomAccessIterator __result, _Map __map) {
-  using __value_type = __iterator_value_type<_ForwardIterator>;
+  using __value_type = __iter_value_t<_ForwardIterator>;
   using __traits     = __counting_sort_traits<__value_type, _Map>;
 
-  __iterator_difference_type<_RandomAccessIterator> __counters[__traits::__value_range + 1] = {0};
+  __iter_difference_t<_RandomAccessIterator> __counters[__traits::__value_range + 1] = {0};
 
   std::__collect(__first, __last, __map, std::next(std::begin(__counters)));
   std::__dispose(__first, __last, __result, __map, std::begin(__counters));
@@ -229,8 +229,7 @@ template <
     class _RandomAccessIterator2,
     class _Map,
     class _Radix,
-    enable_if_t<__radix_sort_traits<__iterator_value_type<_RandomAccessIterator1>, _Map, _Radix>::__radix_count == 1,
-                int> = 0>
+    enable_if_t<__radix_sort_traits<__iter_value_t<_RandomAccessIterator1>, _Map, _Radix>::__radix_count == 1, int> = 0>
 _LIBCPP_HIDE_FROM_ABI constexpr void __radix_sort_impl(
     _RandomAccessIterator1 __first,
     _RandomAccessIterator1 __last,
@@ -244,25 +243,25 @@ _LIBCPP_HIDE_FROM_ABI constexpr void __radix_sort_impl(
   std::move(__buffer, __buffer_end, __first);
 }
 
-template <class _RandomAccessIterator1,
-          class _RandomAccessIterator2,
-          class _Map,
-          class _Radix,
-          enable_if_t<
-              __radix_sort_traits<__iterator_value_type<_RandomAccessIterator1>, _Map, _Radix>::__radix_count % 2 == 0,
-              int> = 0>
+template <
+    class _RandomAccessIterator1,
+    class _RandomAccessIterator2,
+    class _Map,
+    class _Radix,
+    enable_if_t<__radix_sort_traits<__iter_value_t<_RandomAccessIterator1>, _Map, _Radix>::__radix_count % 2 == 0,
+                int> = 0>
 _LIBCPP_HIDE_FROM_ABI constexpr void __radix_sort_impl(
     _RandomAccessIterator1 __first,
     _RandomAccessIterator1 __last,
     _RandomAccessIterator2 __buffer_begin,
     _Map __map,
     _Radix __radix) {
-  using __value_type = __iterator_value_type<_RandomAccessIterator1>;
+  using __value_type = __iter_value_t<_RandomAccessIterator1>;
   using __traits     = __radix_sort_traits<__value_type, _Map, _Radix>;
 
-  __iterator_difference_type<_RandomAccessIterator1>
-      __counters[__traits::__radix_count][__traits::__radix_value_range]                 = {{0}};
-  __iterator_difference_type<_RandomAccessIterator1> __maximums[__traits::__radix_count] = {0};
+  __iter_difference_t<_RandomAccessIterator1> __counters[__traits::__radix_count][__traits::__radix_value_range] = {
+      {0}};
+  __iter_difference_t<_RandomAccessIterator1> __maximums[__traits::__radix_count] = {0};
   const auto __is_sorted = std::__collect(__first, __last, __map, __radix, __counters, __maximums);
   if (!__is_sorted) {
     const auto __range_size = std::distance(__first, __last);
diff --git a/libcxx/include/__algorithm/ranges_count.h b/libcxx/include/__algorithm/ranges_count.h
index 2b3969e763079..30edde87cf82b 100644
--- a/libcxx/include/__algorithm/ranges_count.h
+++ b/libcxx/include/__algorithm/ranges_count.h
@@ -10,13 +10,11 @@
 #define _LIBCPP___ALGORITHM_RANGES_COUNT_H
 
 #include <__algorithm/count.h>
-#include <__algorithm/iterator_operations.h>
 #include <__config>
 #include <__functional/identity.h>
 #include <__functional/ranges_operations.h>
 #include <__iterator/concepts.h>
 #include <__iterator/incrementable_traits.h>
-#include <__iterator/iterator_traits.h>
 #include <__iterator/projected.h>
 #include <__ranges/access.h>
 #include <__ranges/concepts.h>
@@ -39,14 +37,14 @@ struct __count {
     requires indirect_binary_predicate<ranges::equal_to, projected<_Iter, _Proj>, const _Type*>
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Iter>
   operator()(_Iter __first, _Sent __last, const _Type& __value, _Proj __proj = {}) const {
-    return std::__count<_RangeAlgPolicy>(std::move(__first), std::move(__last), __value, __proj);
+    return std::__count(std::move(__first), std::move(__last), __value, __proj);
   }
 
   template <input_range _Range, class _Type, class _Proj = identity>
     requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<_Range>, _Proj>, const _Type*>
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr range_difference_t<_Range>
   operator()(_Range&& __r, const _Type& __value, _Proj __proj = {}) const {
-    return std::__count<_RangeAlgPolicy>(ranges::begin(__r), ranges::end(__r), __value, __proj);
+    return std::__count(ranges::begin(__r), ranges::end(__r), __value, __proj);
   }
 };
 
diff --git a/libcxx/include/__algorithm/ranges_count_if.h b/libcxx/include/__algorithm/ranges_count_if.h
index 6adeb78582bf3..e7b0c17c85d59 100644
--- a/libcxx/include/__algorithm/ranges_count_if.h
+++ b/libcxx/include/__algorithm/ranges_count_if.h
@@ -41,7 +41,7 @@ struct __count_if {
             indirect_unary_predicate<projected<_Iter, _Proj>> _Predicate>
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Iter>
   operator()(_Iter __first, _Sent __last, _Predicate __pred, _Proj __proj = {}) const {
-    return std::__count_if<_RangeAlgPolicy>(std::move(__first), std::move(__last), __pred, __proj);
+    return std::__count_if(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Range,
@@ -49,7 +49,7 @@ struct __count_if {
             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Predicate>
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr range_difference_t<_Range>
   operator()(_Range&& __r, _Predicate __pred, _Proj __proj = {}) const {
-    return std::__count_if<_RangeAlgPolicy>(ranges::begin(__r), ranges::end(__r), __pred, __proj);
+    return std::__count_if(ranges::begin(__r), ranges::end(__r), __pred, __proj);
   }
 };
 
diff --git a/libcxx/include/__algorithm/ranges_unique_copy.h b/libcxx/include/__algorithm/ranges_unique_copy.h
index ee7f0a0187b73..0384758eb5fee 100644
--- a/libcxx/include/__algorithm/ranges_unique_copy.h
+++ b/libcxx/include/__algorithm/ranges_unique_copy.h
@@ -73,7 +73,7 @@ struct __unique_copy {
               indirectly_copyable_storable<_InIter, _OutIter>)
   _LIBCPP_HIDE_FROM_ABI constexpr unique_copy_result<_InIter, _OutIter>
   operator()(_InIter __first, _Sent __last, _OutIter __result, _Comp __comp = {}, _Proj __proj = {}) const {
-    auto __ret = std::__unique_copy<_RangeAlgPolicy>(
+    auto __ret = std::__unique_copy(
         std::move(__first),
         std::move(__last),
         std::move(__result),
@@ -92,7 +92,7 @@ struct __unique_copy {
               indirectly_copyable_storable<iterator_t<_Range>, _OutIter>)
   _LIBCPP_HIDE_FROM_ABI constexpr unique_copy_result<borrowed_iterator_t<_Range>, _OutIter>
   operator()(_Range&& __range, _OutIter __result, _Comp __comp = {}, _Proj __proj = {}) const {
-    auto __ret = std::__unique_copy<_RangeAlgPolicy>(
+    auto __ret = std::__unique_copy(
         ranges::begin(__range),
         ranges::end(__range),
         std::move(__result),
diff --git a/libcxx/include/__algorithm/sample.h b/libcxx/include/__algorithm/sample.h
index ebe5180b7eeca..7b3755082492e 100644
--- a/libcxx/include/__algorithm/sample.h
+++ b/libcxx/include/__algorithm/sample.h
@@ -92,7 +92,7 @@ _LIBCPP_HIDE_FROM_ABI _SampleIterator __sample(
   _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__n >= 0, "N must be a positive number.");
 
   using _PopIterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_PopulationIterator>;
-  using _Difference      = typename _IterOps<_AlgPolicy>::template __difference_type<_PopulationIterator>;
+  using _Difference      = __iter_difference_t<_PopulationIterator>;
   using _CommonType      = typename common_type<_Distance, _Difference>::type;
 
   return std::__sample<_AlgPolicy>(
diff --git a/libcxx/include/__algorithm/sift_down.h b/libcxx/include/__algorithm/sift_down.h
index f82775457540a..6eafa1ce645a9 100644
--- a/libcxx/include/__algorithm/sift_down.h
+++ b/libcxx/include/__algorithm/sift_down.h
@@ -28,8 +28,8 @@ template <class _AlgPolicy, bool __assume_both_children, class _Compare, class _
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
 __sift_down(_RandomAccessIterator __first,
             _Compare&& __comp,
-            __iterator_difference_type<_RandomAccessIterator> __len,
-            __iterator_difference_type<_RandomAccessIterator> __start) {
+            __iter_difference_t<_RandomAccessIterator> __len,
+            __iter_difference_t<_RandomAccessIterator> __start) {
   using _Ops = _IterOps<_AlgPolicy>;
 
   typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
diff --git a/libcxx/include/__algorithm/stable_sort.h b/libcxx/include/__algorithm/stable_sort.h
index 64c808083491e..e427209e9625d 100644
--- a/libcxx/include/__algorithm/stable_sort.h
+++ b/libcxx/include/__algorithm/stable_sort.h
@@ -247,7 +247,7 @@ _LIBCPP_CONSTEXPR_SINCE_CXX26 void __stable_sort(
   constexpr auto __default_comp = __desugars_to_v<__less_tag, _Compare, value_type, value_type >;
   constexpr auto __radix_sortable =
       __is_ordered_integer_representable_v<value_type> &&
-      is_same_v< value_type&, __iterator_reference<_RandomAccessIterator>>;
+      is_same_v< value_type&, __iter_reference_t<_RandomAccessIterator>>;
   if constexpr (__default_comp && __radix_sortable) {
     if (__len <= __buff_size && __len >= static_cast<difference_type>(std::__radix_sort_min_bound<value_type>()) &&
         __len <= static_cast<difference_type>(std::__radix_sort_max_bound<value_type>())) {
diff --git a/libcxx/include/__algorithm/unique_copy.h b/libcxx/include/__algorithm/unique_copy.h
index 16ce80cab32f0..d591b8b3c7045 100644
--- a/libcxx/include/__algorithm/unique_copy.h
+++ b/libcxx/include/__algorithm/unique_copy.h
@@ -36,7 +36,7 @@ struct __read_from_tmp_value_tag {};
 
 } // namespace __unique_copy_tags
 
-template <class _AlgPolicy, class _BinaryPredicate, class _InputIterator, class _Sent, class _OutputIterator>
+template <class _BinaryPredicate, class _InputIterator, class _Sent, class _OutputIterator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI pair<_InputIterator, _OutputIterator>
 __unique_copy(_InputIterator __first,
               _Sent __last,
@@ -44,7 +44,7 @@ __unique_copy(_InputIterator __first,
               _BinaryPredicate&& __pred,
               __unique_copy_tags::__read_from_tmp_value_tag) {
   if (__first != __last) {
-    typename _IterOps<_AlgPolicy>::template __value_type<_InputIterator> __t(*__first);
+    __iter_value_t<_InputIterator> __t(*__first);
     *__result = __t;
     ++__result;
     while (++__first != __last) {
@@ -58,7 +58,7 @@ __unique_copy(_InputIterator __first,
   return pair<_InputIterator, _OutputIterator>(std::move(__first), std::move(__result));
 }
 
-template <class _AlgPolicy, class _BinaryPredicate, class _ForwardIterator, class _Sent, class _OutputIterator>
+template <class _BinaryPredicate, class _ForwardIterator, class _Sent, class _OutputIterator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI pair<_ForwardIterator, _OutputIterator>
 __unique_copy(_ForwardIterator __first,
               _Sent __last,
@@ -80,7 +80,7 @@ __unique_copy(_ForwardIterator __first,
   return pair<_ForwardIterator, _OutputIterator>(std::move(__first), std::move(__result));
 }
 
-template <class _AlgPolicy, class _BinaryPredicate, class _InputIterator, class _Sent, class _InputAndOutputIterator>
+template <class _BinaryPredicate, class _InputIterator, class _Sent, class _InputAndOutputIterator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI pair<_InputIterator, _InputAndOutputIterator>
 __unique_copy(_InputIterator __first,
               _Sent __last,
@@ -109,7 +109,7 @@ unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __res
                        typename iterator_traits<_OutputIterator>::value_type>::value,
           __unique_copy_tags::__reread_from_output_tag,
           __unique_copy_tags::__read_from_tmp_value_tag> >;
-  return std::__unique_copy<_ClassicAlgPolicy>(
+  return std::__unique_copy(
              std::move(__first), std::move(__last), std::move(__result), __pred, __algo_tag())
       .second;
 }
diff --git a/libcxx/include/__debug_utils/strict_weak_ordering_check.h b/libcxx/include/__debug_utils/strict_weak_ordering_check.h
index 3724ca95c5d42..9e67605b2631a 100644
--- a/libcxx/include/__debug_utils/strict_weak_ordering_check.h
+++ b/libcxx/include/__debug_utils/strict_weak_ordering_check.h
@@ -27,7 +27,7 @@ template <class _RandomAccessIterator, class _Comp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
 __check_strict_weak_ordering_sorted(_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp& __comp) {
 #if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
-  using __diff_t  = __iterator_difference_type<_RandomAccessIterator>;
+  using __diff_t  = __iter_difference_t<_RandomAccessIterator>;
   using _Comp_ref = __comp_ref_type<_Comp>;
   if (!__libcpp_is_constant_evaluated()) {
     // Check if the range is actually sorted.
diff --git a/libcxx/include/__flat_set/flat_multiset.h b/libcxx/include/__flat_set/flat_multiset.h
index 5cfa38fb41057..3159091fd3131 100644
--- a/libcxx/include/__flat_set/flat_multiset.h
+++ b/libcxx/include/__flat_set/flat_multiset.h
@@ -718,15 +718,15 @@ template <class _KeyContainer, class _Compare, class _Allocator>
 flat_multiset(sorted_equivalent_t, _KeyContainer, _Compare, _Allocator)
     -> flat_multiset<typename _KeyContainer::value_type, _Compare, _KeyContainer>;
 
-template <class _InputIterator, class _Compare = less<__iterator_value_type<_InputIterator>>>
+template <class _InputIterator, class _Compare = less<__iter_value_t<_InputIterator>>>
   requires(__has_input_iterator_category<_InputIterator>::value && !__is_allocator_v<_Compare>)
 flat_multiset(_InputIterator, _InputIterator, _Compare = _Compare())
-    -> flat_multiset<__iterator_value_type<_InputIterator>, _Compare>;
+    -> flat_multiset<__iter_value_t<_InputIterator>, _Compare>;
 
-template <class _InputIterator, class _Compare = less<__iterator_value_type<_InputIterator>>>
+template <class _InputIterator, class _Compare = less<__iter_value_t<_InputIterator>>>
   requires(__has_input_iterator_category<_InputIterator>::value && !__is_allocator_v<_Compare>)
 flat_multiset(sorted_equivalent_t, _InputIterator, _InputIterator, _Compare = _Compare())
-    -> flat_multiset<__iterator_value_type<_InputIterator>, _Compare>;
+    -> flat_multiset<__iter_value_t<_InputIterator>, _Compare>;
 
 template <ranges::input_range _Range,
           class _Compare   = less<ranges::range_value_t<_Range>>,
diff --git a/libcxx/include/__flat_set/flat_set.h b/libcxx/include/__flat_set/flat_set.h
index 0c8fdb5a803c8..11ff5617de23f 100644
--- a/libcxx/include/__flat_set/flat_set.h
+++ b/libcxx/include/__flat_set/flat_set.h
@@ -807,15 +807,14 @@ template <class _KeyContainer, class _Compare, class _Allocator>
 flat_set(sorted_unique_t, _KeyContainer, _Compare, _Allocator)
     -> flat_set<typename _KeyContainer::value_type, _Compare, _KeyContainer>;
 
-template <class _InputIterator, class _Compare = less<__iterator_value_type<_InputIterator>>>
+template <class _InputIterator, class _Compare = less<__iter_value_t<_InputIterator>>>
   requires(__has_input_iterator_category<_InputIterator>::value && !__is_allocator_v<_Compare>)
-flat_set(_InputIterator, _InputIterator, _Compare = _Compare())
-    -> flat_set<__iterator_value_type<_InputIterator>, _Compare>;
+flat_set(_InputIterator, _InputIterator, _Compare = _Compare()) -> flat_set<__iter_value_t<_InputIterator>, _Compare>;
 
-template <class _InputIterator, class _Compare = less<__iterator_value_type<_InputIterator>>>
+template <class _InputIterator, class _Compare = less<__iter_value_t<_InputIterator>>>
   requires(__has_input_iterator_category<_InputIterator>::value && !__is_allocator_v<_Compare>)
 flat_set(sorted_unique_t, _InputIterator, _InputIterator, _Compare = _Compare())
-    -> flat_set<__iterator_value_type<_InputIterator>, _Compare>;
+    -> flat_set<__iter_value_t<_InputIterator>, _Compare>;
 
 template <ranges::input_range _Range,
           class _Compare   = less<ranges::range_value_t<_Range>>,
diff --git a/libcxx/include/__iterator/bounded_iter.h b/libcxx/include/__iterator/bounded_iter.h
index d2a09061126bd..65ed1ca3aaada 100644
--- a/libcxx/include/__iterator/bounded_iter.h
+++ b/libcxx/include/__iterator/bounded_iter.h
@@ -77,8 +77,8 @@ struct __bounded_iter {
   template <class _OtherIterator,
             __enable_if_t<
                 _And<is_convertible<const _OtherIterator&, _Iterator>,
-                     _Or<is_same<reference, __iterator_reference<_OtherIterator> >,
-                         is_same<reference, __make_const_lvalue_ref<__iterator_reference<_OtherIterator> > > > >::value,
+                     _Or<is_same<reference, __iter_reference_t<_OtherIterator> >,
+                         is_same<reference, __make_const_lvalue_ref<__iter_reference_t<_OtherIterator> > > > >::value,
                 int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __bounded_iter(__bounded_iter<_OtherIterator> const& __other) _NOEXCEPT
       : __current_(__other.__current_),
diff --git a/libcxx/include/__iterator/cpp17_iterator_concepts.h b/libcxx/include/__iterator/cpp17_iterator_concepts.h
index ecd30d8e11680..b2a506b02008e 100644
--- a/libcxx/include/__iterator/cpp17_iterator_concepts.h
+++ b/libcxx/include/__iterator/cpp17_iterator_concepts.h
@@ -68,8 +68,7 @@ concept __cpp17_default_constructible = is_default_constructible_v<_Tp>;
 template <class _Iter>
 concept __cpp17_iterator =
     __cpp17_copy_constructible<_Iter> && __cpp17_copy_assignable<_Iter> && __cpp17_destructible<_Iter> &&
-    (is_signed_v<__iterator_difference_type<_Iter>> || is_void_v<__iterator_difference_type<_Iter>>) &&
-    requires(_Iter __iter) {
+    (is_signed_v<__iter_difference_t<_Iter>> || is_void_v<__iter_difference_t<_Iter>>) && requires(_Iter __iter) {
       { *__iter };
       { ++__iter } -> same_as<_Iter&>;
     };
@@ -82,8 +81,8 @@ concept __cpp17_input_iterator =
       { __lhs != std::as_const(__rhs) } -> __boolean_testable;
       { std::as_const(__lhs) != std::as_const(__rhs) } -> __boolean_testable;
 
-      { *__lhs } -> same_as<__iterator_reference<_Iter>>;
-      { *std::as_const(__lhs) } -> same_as<__iterator_reference<_Iter>>;
+      { *__lhs } -> same_as<typename iterator_traits<_Iter>::reference>;
+      { *std::as_const(__lhs) } -> same_as<typename iterator_traits<_Iter>::reference>;
 
       { ++__lhs } -> same_as<_Iter&>;
       { (void)__lhs++ };
@@ -102,19 +101,19 @@ template <class _Iter>
 concept __cpp17_forward_iterator =
     __cpp17_input_iterator<_Iter> && __cpp17_default_constructible<_Iter> && requires(_Iter __iter) {
       { __iter++ } -> convertible_to<const _Iter&>;
-      { *__iter++ } -> same_as<__iterator_reference<_Iter>>;
+      { *__iter++ } -> same_as<typename iterator_traits<_Iter>::reference>;
     };
 
 template <class _Iter>
 concept __cpp17_bidirectional_iterator = __cpp17_forward_iterator<_Iter> && requires(_Iter __iter) {
   { --__iter } -> same_as<_Iter&>;
   { __iter-- } -> convertible_to<const _Iter&>;
-  { *__iter-- } -> same_as<__iterator_reference<_Iter>>;
+  { *__iter-- } -> same_as<typename iterator_traits<_Iter>::reference>;
 };
 
 template <class _Iter>
 concept __cpp17_random_access_iterator =
-    __cpp17_bidirectional_iterator<_Iter> && requires(_Iter __iter, __iterator_difference_type<_Iter> __n) {
+    __cpp17_bidirectional_iterator<_Iter> && requires(_Iter __iter, __iter_difference_t<_Iter> __n) {
       { __iter += __n } -> same_as<_Iter&>;
 
       { __iter + __n } -> same_as<_Iter>;
@@ -126,13 +125,13 @@ concept __cpp17_random_access_iterator =
       { __iter - __n } -> same_as<_Iter>;
       { std::as_const(__iter) - __n } -> same_as<_Iter>;
 
-      { __iter - __iter } -> same_as<__iterator_difference_type<_Iter>>;
-      { std::as_const(__iter) - __iter } -> same_as<__iterator_difference_type<_Iter>>;
-      { __iter - std::as_const(__iter) } -> same_as<__iterator_difference_type<_Iter>>;
-      { std::as_const(__iter) - std::as_const(__iter) } -> same_as<__iterator_difference_type<_Iter>>;
+      { __iter - __iter } -> same_as<__iter_difference_t<_Iter>>;
+      { std::as_const(__iter) - __iter } -> same_as<__iter_difference_t<_Iter>>;
+      { __iter - std::as_const(__iter) } -> same_as<__iter_difference_t<_Iter>>;
+      { std::as_const(__iter) - std::as_const(__iter) } -> same_as<__iter_difference_t<_Iter>>;
 
-      { __iter[__n] } -> convertible_to<__iterator_reference<_Iter>>;
-      { std::as_const(__iter)[__n] } -> convertible_to<__iterator_reference<_Iter>>;
+      { __iter[__n] } -> convertible_to<typename iterator_traits<_Iter>::reference>;
+      { std::as_const(__iter)[__n] } -> convertible_to<typename iterator_traits<_Iter>::reference>;
 
       { __iter < __iter } -> __boolean_testable;
       { std::as_const(__iter) < __iter } -> __boolean_testable;
diff --git a/libcxx/include/__iterator/iterator_traits.h b/libcxx/include/__iterator/iterator_traits.h
index ebf315a53b6b7..7d5149a794963 100644
--- a/libcxx/include/__iterator/iterator_traits.h
+++ b/libcxx/include/__iterator/iterator_traits.h
@@ -46,6 +46,9 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+template <class _Iter>
+using __iter_reference_t _LIBCPP_NODEBUG = decltype(*std::declval<_Iter&>());
+
 #if _LIBCPP_STD_VER >= 20
 
 template <class _Tp>
@@ -55,7 +58,7 @@ concept __dereferenceable = requires(_Tp& __t) {
 
 // [iterator.traits]
 template <__dereferenceable _Tp>
-using iter_reference_t = decltype(*std::declval<_Tp&>());
+using iter_reference_t = __iter_reference_t<_Tp>;
 
 #endif // _LIBCPP_STD_VER >= 20
 
@@ -419,31 +422,60 @@ using __has_exactly_bidirectional_iterator_category _LIBCPP_NODEBUG =
                       __has_iterator_category_convertible_to<_Tp, bidirectional_iterator_tag>::value &&
                           !__has_iterator_category_convertible_to<_Tp, random_access_iterator_tag>::value>;
 
-template <class _InputIterator>
-using __iterator_value_type _LIBCPP_NODEBUG = typename iterator_traits<_InputIterator>::value_type;
+#if _LIBCPP_STD_VER >= 20
+
+// [readable.traits]
+
+// Let `RI` be `remove_cvref_t<I>`. The type `iter_value_t<I>` denotes
+// `indirectly_readable_traits<RI>::value_type` if `iterator_traits<RI>` names a specialization
+// generated from the primary template, and `iterator_traits<RI>::value_type` otherwise.
+// This has to be in this file and not readable_traits.h to break the include cycle between the two.
+template <class _Ip>
+using iter_value_t =
+    typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value,
+                           indirectly_readable_traits<remove_cvref_t<_Ip> >,
+                           iterator_traits<remove_cvref_t<_Ip> > >::value_type;
+
+template <class _Iter>
+using __iter_value_t _LIBCPP_NODEBUG = iter_value_t<_Iter>;
+
+template <class _Iter>
+using __iter_difference_t _LIBCPP_NODEBUG = iter_difference_t<_Iter>;
+
+template <class _Iter>
+using __iter_reference_t _LIBCPP_NODEBUG = iter_reference_t<_Iter>;
+
+#else
+
+template <class _Iter>
+using __iter_value_t = typename iterator_traits<_Iter>::value_type;
+
+template <class _Iter>
+using __iter_difference_t = typename iterator_traits<_Iter>::difference_type;
+
+#endif // _LIBCPP_STD_VER >= 20
 
 #if _LIBCPP_STD_VER >= 23
 template <class _InputIterator>
-using __iter_key_type _LIBCPP_NODEBUG = remove_const_t<tuple_element_t<0, __iterator_value_type<_InputIterator>>>;
+using __iter_key_type _LIBCPP_NODEBUG = remove_const_t<tuple_element_t<0, __iter_value_t<_InputIterator>>>;
 
 template <class _InputIterator>
-using __iter_mapped_type _LIBCPP_NODEBUG = tuple_element_t<1, __iterator_value_type<_InputIterator>>;
+using __iter_mapped_type _LIBCPP_NODEBUG = tuple_element_t<1, __iter_value_t<_InputIterator>>;
 
 template <class _InputIterator>
 using __iter_to_alloc_type _LIBCPP_NODEBUG =
-    pair<const tuple_element_t<0, __iterator_value_type<_InputIterator>>,
-         tuple_element_t<1, __iterator_value_type<_InputIterator>>>;
+    pair<const tuple_element_t<0, __iter_value_t<_InputIterator>>, tuple_element_t<1, __iter_value_t<_InputIterator>>>;
 #else
 template <class _InputIterator>
-using __iter_key_type _LIBCPP_NODEBUG = __remove_const_t<typename __iterator_value_type<_InputIterator>::first_type>;
+using __iter_key_type _LIBCPP_NODEBUG = __remove_const_t<typename __iter_value_t<_InputIterator>::first_type>;
 
 template <class _InputIterator>
-using __iter_mapped_type _LIBCPP_NODEBUG = typename __iterator_value_type<_InputIterator>::second_type;
+using __iter_mapped_type _LIBCPP_NODEBUG = typename __iter_value_t<_InputIterator>::second_type;
 
 template <class _InputIterator>
 using __iter_to_alloc_type _LIBCPP_NODEBUG =
-    pair<const typename __iterator_value_type<_InputIterator>::first_type,
-         typename __iterator_value_type<_InputIterator>::second_type>;
+    pair<const typename __iter_value_t<_InputIterator>::first_type,
+         typename __iter_value_t<_InputIterator>::second_type>;
 #endif // _LIBCPP_STD_VER >= 23
 
 template <class _Iter>
@@ -452,28 +484,6 @@ using __iterator_iterator_category _LIBCPP_NODEBUG = typename iterator_traits<_I
 template <class _Iter>
 using __iterator_pointer _LIBCPP_NODEBUG = typename iterator_traits<_Iter>::pointer;
 
-template <class _Iter>
-using __iterator_difference_type _LIBCPP_NODEBUG = typename iterator_traits<_Iter>::difference_type;
-
-template <class _Iter>
-using __iterator_reference _LIBCPP_NODEBUG = typename iterator_traits<_Iter>::reference;
-
-#if _LIBCPP_STD_VER >= 20
-
-// [readable.traits]
-
-// Let `RI` be `remove_cvref_t<I>`. The type `iter_value_t<I>` denotes
-// `indirectly_readable_traits<RI>::value_type` if `iterator_traits<RI>` names a specialization
-// generated from the primary template, and `iterator_traits<RI>::value_type` otherwise.
-// This has to be in this file and not readable_traits.h to break the include cycle between the two.
-template <class _Ip>
-using iter_value_t =
-    typename conditional_t<__is_primary_template<iterator_traits<remove_cvref_t<_Ip> > >::value,
-                           indirectly_readable_traits<remove_cvref_t<_Ip> >,
-                           iterator_traits<remove_cvref_t<_Ip> > >::value_type;
-
-#endif // _LIBCPP_STD_VER >= 20
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ITERATOR_ITERATOR_TRAITS_H
diff --git a/libcxx/include/__iterator/static_bounded_iter.h b/libcxx/include/__iterator/static_bounded_iter.h
index d8fc7d185e7bc..8968ba4079043 100644
--- a/libcxx/include/__iterator/static_bounded_iter.h
+++ b/libcxx/include/__iterator/static_bounded_iter.h
@@ -100,8 +100,8 @@ struct __static_bounded_iter {
   template <class _OtherIterator,
             __enable_if_t<
                 _And<is_convertible<const _OtherIterator&, _Iterator>,
-                     _Or<is_same<reference, __iterator_reference<_OtherIterator> >,
-                         is_same<reference, __make_const_lvalue_ref<__iterator_reference<_OtherIterator> > > > >::value,
+                     _Or<is_same<reference, __iter_reference_t<_OtherIterator> >,
+                         is_same<reference, __make_const_lvalue_ref<__iter_reference_t<_OtherIterator> > > > >::value,
                 int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
   __static_bounded_iter(__static_bounded_iter<_OtherIterator, _Size> const& __other) _NOEXCEPT
diff --git a/libcxx/include/__iterator/wrap_iter.h b/libcxx/include/__iterator/wrap_iter.h
index d18d9682da449..e3993bb5ee013 100644
--- a/libcxx/include/__iterator/wrap_iter.h
+++ b/libcxx/include/__iterator/wrap_iter.h
@@ -49,12 +49,12 @@ class __wrap_iter {
 
 public:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __wrap_iter() _NOEXCEPT : __i_() {}
-  template <class _OtherIter,
-            __enable_if_t<
-                _And<is_convertible<const _OtherIter&, _Iter>,
-                     _Or<is_same<reference, __iterator_reference<_OtherIter> >,
-                         is_same<reference, __make_const_lvalue_ref<__iterator_reference<_OtherIter> > > > >::value,
-                int> = 0>
+  template <
+      class _OtherIter,
+      __enable_if_t<_And<is_convertible<const _OtherIter&, _Iter>,
+                         _Or<is_same<reference, __iter_reference_t<_OtherIter> >,
+                             is_same<reference, __make_const_lvalue_ref<__iter_reference_t<_OtherIter> > > > >::value,
+                    int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __wrap_iter(const __wrap_iter<_OtherIter>& __u) _NOEXCEPT
       : __i_(__u.__i_) {}
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 reference operator*() const _NOEXCEPT { return *__i_; }
diff --git a/libcxx/include/__numeric/pstl.h b/libcxx/include/__numeric/pstl.h
index fe7b2cc7a82cc..d49f51cd715cb 100644
--- a/libcxx/include/__numeric/pstl.h
+++ b/libcxx/include/__numeric/pstl.h
@@ -70,7 +70,7 @@ template <class _ExecutionPolicy,
           class _ForwardIterator,
           class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
           enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI __iterator_value_type<_ForwardIterator>
+_LIBCPP_HIDE_FROM_ABI __iter_value_t<_ForwardIterator>
 reduce(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last) {
   _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "reduce requires ForwardIterators");
   using _Implementation = __pstl::__dispatch<__pstl::__reduce, __pstl::__current_configuration, _RawPolicy>;
@@ -78,7 +78,7 @@ reduce(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator _
       std::forward<_ExecutionPolicy>(__policy),
       std::move(__first),
       std::move(__last),
-      __iterator_value_type<_ForwardIterator>(),
+      __iter_value_t<_ForwardIterator>(),
       plus{});
 }
 
diff --git a/libcxx/include/__pstl/backends/default.h b/libcxx/include/__pstl/backends/default.h
index 43b1f1ce3870a..aa32c561510e9 100644
--- a/libcxx/include/__pstl/backends/default.h
+++ b/libcxx/include/__pstl/backends/default.h
@@ -102,7 +102,7 @@ struct __find<__default_backend_tag, _ExecutionPolicy> {
   operator()(_Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) const noexcept {
     using _FindIf = __dispatch<__find_if, __current_configuration, _ExecutionPolicy>;
     return _FindIf()(
-        __policy, std::move(__first), std::move(__last), [&](__iterator_reference<_ForwardIterator> __element) {
+        __policy, std::move(__first), std::move(__last), [&](__iter_reference_t<_ForwardIterator> __element) {
           return __element == __value;
         });
   }
@@ -137,7 +137,7 @@ struct __all_of<__default_backend_tag, _ExecutionPolicy> {
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
   operator()(_Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Pred&& __pred) const noexcept {
     using _AnyOf = __dispatch<__any_of, __current_configuration, _ExecutionPolicy>;
-    auto __res   = _AnyOf()(__policy, __first, __last, [&](__iterator_reference<_ForwardIterator> __value) {
+    auto __res   = _AnyOf()(__policy, __first, __last, [&](__iter_reference_t<_ForwardIterator> __value) {
       return !__pred(__value);
     });
     if (!__res)
@@ -204,7 +204,7 @@ struct __fill<__default_backend_tag, _ExecutionPolicy> {
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
   operator()(_Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Tp const& __value) const noexcept {
     using _ForEach = __dispatch<__for_each, __current_configuration, _ExecutionPolicy>;
-    using _Ref     = __iterator_reference<_ForwardIterator>;
+    using _Ref     = __iter_reference_t<_ForwardIterator>;
     return _ForEach()(__policy, std::move(__first), std::move(__last), [&](_Ref __element) { __element = __value; });
   }
 };
@@ -233,7 +233,7 @@ struct __replace<__default_backend_tag, _ExecutionPolicy> {
   operator()(_Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Tp const& __old, _Tp const& __new)
       const noexcept {
     using _ReplaceIf = __dispatch<__replace_if, __current_configuration, _ExecutionPolicy>;
-    using _Ref       = __iterator_reference<_ForwardIterator>;
+    using _Ref       = __iter_reference_t<_ForwardIterator>;
     return _ReplaceIf()(
         __policy, std::move(__first), std::move(__last), [&](_Ref __element) { return __element == __old; }, __new);
   }
@@ -246,7 +246,7 @@ struct __replace_if<__default_backend_tag, _ExecutionPolicy> {
       _Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Pred&& __pred, _Tp const& __new_value)
       const noexcept {
     using _ForEach = __dispatch<__for_each, __current_configuration, _ExecutionPolicy>;
-    using _Ref     = __iterator_reference<_ForwardIterator>;
+    using _Ref     = __iter_reference_t<_ForwardIterator>;
     return _ForEach()(__policy, std::move(__first), std::move(__last), [&](_Ref __element) {
       if (__pred(__element))
         __element = __new_value;
@@ -260,7 +260,7 @@ struct __generate<__default_backend_tag, _ExecutionPolicy> {
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
   operator()(_Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Generator&& __gen) const noexcept {
     using _ForEach = __dispatch<__for_each, __current_configuration, _ExecutionPolicy>;
-    using _Ref     = __iterator_reference<_ForwardIterator>;
+    using _Ref     = __iter_reference_t<_ForwardIterator>;
     return _ForEach()(__policy, std::move(__first), std::move(__last), [&](_Ref __element) { __element = __gen(); });
   }
 };
@@ -271,7 +271,7 @@ struct __generate_n<__default_backend_tag, _ExecutionPolicy> {
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
   operator()(_Policy&& __policy, _ForwardIterator __first, _Size __n, _Generator&& __gen) const noexcept {
     using _ForEachN = __dispatch<__for_each_n, __current_configuration, _ExecutionPolicy>;
-    using _Ref      = __iterator_reference<_ForwardIterator>;
+    using _Ref      = __iter_reference_t<_ForwardIterator>;
     return _ForEachN()(__policy, std::move(__first), __n, [&](_Ref __element) { __element = __gen(); });
   }
 };
@@ -295,11 +295,11 @@ struct __sort<__default_backend_tag, _ExecutionPolicy> {
 template <class _ExecutionPolicy>
 struct __count_if<__default_backend_tag, _ExecutionPolicy> {
   template <class _Policy, class _ForwardIterator, class _Predicate>
-  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iterator_difference_type<_ForwardIterator>> operator()(
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_difference_t<_ForwardIterator>> operator()(
       _Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate&& __pred) const noexcept {
     using _TransformReduce = __dispatch<__transform_reduce, __current_configuration, _ExecutionPolicy>;
-    using _DiffT           = __iterator_difference_type<_ForwardIterator>;
-    using _Ref             = __iterator_reference<_ForwardIterator>;
+    using _DiffT           = __iter_difference_t<_ForwardIterator>;
+    using _Ref             = __iter_reference_t<_ForwardIterator>;
     return _TransformReduce()(
         __policy, std::move(__first), std::move(__last), _DiffT{}, std::plus{}, [&](_Ref __element) -> _DiffT {
           return __pred(__element) ? _DiffT(1) : _DiffT(0);
@@ -310,10 +310,10 @@ struct __count_if<__default_backend_tag, _ExecutionPolicy> {
 template <class _ExecutionPolicy>
 struct __count<__default_backend_tag, _ExecutionPolicy> {
   template <class _Policy, class _ForwardIterator, class _Tp>
-  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iterator_difference_type<_ForwardIterator>>
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_difference_t<_ForwardIterator>>
   operator()(_Policy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Tp const& __value) const noexcept {
     using _CountIf = __dispatch<__count_if, __current_configuration, _ExecutionPolicy>;
-    using _Ref     = __iterator_reference<_ForwardIterator>;
+    using _Ref     = __iter_reference_t<_ForwardIterator>;
     return _CountIf()(__policy, std::move(__first), std::move(__last), [&](_Ref __element) -> bool {
       return __element == __value;
     });
@@ -402,7 +402,7 @@ struct __replace_copy_if<__default_backend_tag, _ExecutionPolicy> {
              _Pred&& __pred,
              _Tp const& __new_value) const noexcept {
     using _Transform = __dispatch<__transform, __current_configuration, _ExecutionPolicy>;
-    using _Ref       = __iterator_reference<_ForwardIterator>;
+    using _Ref       = __iter_reference_t<_ForwardIterator>;
     auto __res =
         _Transform()(__policy, std::move(__first), std::move(__last), std::move(__out_it), [&](_Ref __element) {
           return __pred(__element) ? __new_value : __element;
@@ -424,7 +424,7 @@ struct __replace_copy<__default_backend_tag, _ExecutionPolicy> {
              _Tp const& __old_value,
              _Tp const& __new_value) const noexcept {
     using _ReplaceCopyIf = __dispatch<__replace_copy_if, __current_configuration, _ExecutionPolicy>;
-    using _Ref           = __iterator_reference<_ForwardIterator>;
+    using _Ref           = __iter_reference_t<_ForwardIterator>;
     return _ReplaceCopyIf()(
         __policy,
         std::move(__first),
diff --git a/libcxx/include/__pstl/backends/libdispatch.h b/libcxx/include/__pstl/backends/libdispatch.h
index 88d4231d29a0a..3439d164e0b7e 100644
--- a/libcxx/include/__pstl/backends/libdispatch.h
+++ b/libcxx/include/__pstl/backends/libdispatch.h
@@ -269,7 +269,7 @@ struct __cpu_traits<__libdispatch_backend_tag> {
       return __empty{};
     }
 
-    using _Value = __iterator_value_type<_RandomAccessIterator>;
+    using _Value = __iter_value_t<_RandomAccessIterator>;
 
     auto __destroy = [__size](_Value* __ptr) {
       std::destroy_n(__ptr, __size);
@@ -282,7 +282,7 @@ struct __cpu_traits<__libdispatch_backend_tag> {
     // Initialize all elements to a moved-from state
     // TODO: Don't do this - this can be done in the first merge - see https://llvm.org/PR63928
     std::__construct_at(__values.get(), std::move(*__first));
-    for (__iterator_difference_type<_RandomAccessIterator> __i = 1; __i != __size; ++__i) {
+    for (__iter_difference_t<_RandomAccessIterator> __i = 1; __i != __size; ++__i) {
       std::__construct_at(__values.get() + __i, std::move(__values.get()[__i - 1]));
     }
     *__first = std::move(__values.get()[__size - 1]);
diff --git a/libcxx/include/__pstl/cpu_algos/find_if.h b/libcxx/include/__pstl/cpu_algos/find_if.h
index aae64b66eb0c0..03953b57575e2 100644
--- a/libcxx/include/__pstl/cpu_algos/find_if.h
+++ b/libcxx/include/__pstl/cpu_algos/find_if.h
@@ -119,7 +119,7 @@ struct __cpu_parallel_find_if {
           true);
     } else if constexpr (__is_unsequenced_execution_policy_v<_RawExecutionPolicy> &&
                          __has_random_access_iterator_category_or_concept<_ForwardIterator>::value) {
-      using __diff_t = __iterator_difference_type<_ForwardIterator>;
+      using __diff_t = __iter_difference_t<_ForwardIterator>;
       return __pstl::__simd_first<_Backend>(
           __first, __diff_t(0), __last - __first, [&__pred](_ForwardIterator __iter, __diff_t __i) {
             return __pred(__iter[__i]);
diff --git a/libcxx/include/__pstl/cpu_algos/transform.h b/libcxx/include/__pstl/cpu_algos/transform.h
index 30d117d754b31..63191f83f79b5 100644
--- a/libcxx/include/__pstl/cpu_algos/transform.h
+++ b/libcxx/include/__pstl/cpu_algos/transform.h
@@ -84,8 +84,9 @@ struct __cpu_parallel_transform {
           __first,
           __last - __first,
           __result,
-          [&](__iterator_reference<_ForwardIterator> __in_value,
-              __iterator_reference<_ForwardOutIterator> __out_value) { __out_value = __op(__in_value); });
+          [&](__iter_reference_t<_ForwardIterator> __in_value, __iter_reference_t<_ForwardOutIterator> __out_value) {
+            __out_value = __op(__in_value);
+          });
     } else {
       return std::transform(__first, __last, __result, __op);
     }
@@ -137,9 +138,9 @@ struct __cpu_parallel_transform_binary {
           __last1 - __first1,
           __first2,
           __result,
-          [&](__iterator_reference<_ForwardIterator1> __in1,
-              __iterator_reference<_ForwardIterator2> __in2,
-              __iterator_reference<_ForwardOutIterator> __out_value) { __out_value = __op(__in1, __in2); });
+          [&](__iter_reference_t<_ForwardIterator1> __in1,
+              __iter_reference_t<_ForwardIterator2> __in2,
+              __iter_reference_t<_ForwardOutIterator> __out_value) { __out_value = __op(__in1, __in2); });
     } else {
       return std::transform(__first1, __last1, __first2, __result, __op);
     }
diff --git a/libcxx/include/__pstl/cpu_algos/transform_reduce.h b/libcxx/include/__pstl/cpu_algos/transform_reduce.h
index edfb28b4466fc..56f737185e939 100644
--- a/libcxx/include/__pstl/cpu_algos/transform_reduce.h
+++ b/libcxx/include/__pstl/cpu_algos/transform_reduce.h
@@ -148,10 +148,9 @@ struct __cpu_parallel_transform_reduce_binary {
                          __has_random_access_iterator_category_or_concept<_ForwardIterator1>::value &&
                          __has_random_access_iterator_category_or_concept<_ForwardIterator2>::value) {
       return __pstl::__simd_transform_reduce<_Backend>(
-          __last1 - __first1,
-          std::move(__init),
-          std::move(__reduce),
-          [&](__iterator_difference_type<_ForwardIterator1> __i) { return __transform(__first1[__i], __first2[__i]); });
+          __last1 - __first1, std::move(__init), std::move(__reduce), [&](__iter_difference_t<_ForwardIterator1> __i) {
+            return __transform(__first1[__i], __first2[__i]);
+          });
     } else {
       return std::transform_reduce(
           std::move(__first1),
@@ -201,7 +200,7 @@ struct __cpu_parallel_transform_reduce {
           __last - __first,
           std::move(__init),
           std::move(__reduce),
-          [=, &__transform](__iterator_difference_type<_ForwardIterator> __i) { return __transform(__first[__i]); });
+          [=, &__transform](__iter_difference_t<_ForwardIterator> __i) { return __transform(__first[__i]); });
     } else {
       return std::transform_reduce(
           std::move(__first), std::move(__last), std::move(__init), std::move(__reduce), std::move(__transform));
diff --git a/libcxx/include/__vector/vector.h b/libcxx/include/__vector/vector.h
index 316d3a9d10eff..f9e7e0b13bdb9 100644
--- a/libcxx/include/__vector/vector.h
+++ b/libcxx/include/__vector/vector.h
@@ -844,16 +844,16 @@ class vector {
 
 #if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Alloc = allocator<__iterator_value_type<_InputIterator>>,
+          class _Alloc = allocator<__iter_value_t<_InputIterator>>,
           class        = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class        = enable_if_t<__is_allocator_v<_Alloc>>>
-vector(_InputIterator, _InputIterator) -> vector<__iterator_value_type<_InputIterator>, _Alloc>;
+vector(_InputIterator, _InputIterator) -> vector<__iter_value_t<_InputIterator>, _Alloc>;
 
 template <class _InputIterator,
           class _Alloc,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class = enable_if_t<__is_allocator_v<_Alloc>>>
-vector(_InputIterator, _InputIterator, _Alloc) -> vector<__iterator_value_type<_InputIterator>, _Alloc>;
+vector(_InputIterator, _InputIterator, _Alloc) -> vector<__iter_value_t<_InputIterator>, _Alloc>;
 #endif
 
 #if _LIBCPP_STD_VER >= 23
diff --git a/libcxx/include/deque b/libcxx/include/deque
index 3e7ee8d8565b6..3df13cd293a51 100644
--- a/libcxx/include/deque
+++ b/libcxx/include/deque
@@ -1259,16 +1259,16 @@ _LIBCPP_CONSTEXPR const typename allocator_traits<_Alloc>::difference_type deque
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Alloc = allocator<__iterator_value_type<_InputIterator>>,
+          class _Alloc = allocator<__iter_value_t<_InputIterator>>,
           class        = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class        = enable_if_t<__is_allocator_v<_Alloc>>>
-deque(_InputIterator, _InputIterator) -> deque<__iterator_value_type<_InputIterator>, _Alloc>;
+deque(_InputIterator, _InputIterator) -> deque<__iter_value_t<_InputIterator>, _Alloc>;
 
 template <class _InputIterator,
           class _Alloc,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class = enable_if_t<__is_allocator_v<_Alloc>>>
-deque(_InputIterator, _InputIterator, _Alloc) -> deque<__iterator_value_type<_InputIterator>, _Alloc>;
+deque(_InputIterator, _InputIterator, _Alloc) -> deque<__iter_value_t<_InputIterator>, _Alloc>;
 #  endif
 
 #  if _LIBCPP_STD_VER >= 23
diff --git a/libcxx/include/forward_list b/libcxx/include/forward_list
index df7da20cfb611..219228b0f14c3 100644
--- a/libcxx/include/forward_list
+++ b/libcxx/include/forward_list
@@ -919,16 +919,16 @@ private:
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Alloc = allocator<__iterator_value_type<_InputIterator>>,
+          class _Alloc = allocator<__iter_value_t<_InputIterator>>,
           class        = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class        = enable_if_t<__is_allocator_v<_Alloc>>>
-forward_list(_InputIterator, _InputIterator) -> forward_list<__iterator_value_type<_InputIterator>, _Alloc>;
+forward_list(_InputIterator, _InputIterator) -> forward_list<__iter_value_t<_InputIterator>, _Alloc>;
 
 template <class _InputIterator,
           class _Alloc,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class = enable_if_t<__is_allocator_v<_Alloc>>>
-forward_list(_InputIterator, _InputIterator, _Alloc) -> forward_list<__iterator_value_type<_InputIterator>, _Alloc>;
+forward_list(_InputIterator, _InputIterator, _Alloc) -> forward_list<__iter_value_t<_InputIterator>, _Alloc>;
 #  endif
 
 #  if _LIBCPP_STD_VER >= 23
diff --git a/libcxx/include/list b/libcxx/include/list
index c5c2a8508999c..8fd8522294cab 100644
--- a/libcxx/include/list
+++ b/libcxx/include/list
@@ -1001,16 +1001,16 @@ private:
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Alloc = allocator<__iterator_value_type<_InputIterator>>,
+          class _Alloc = allocator<__iter_value_t<_InputIterator>>,
           class        = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class        = enable_if_t<__is_allocator_v<_Alloc>>>
-list(_InputIterator, _InputIterator) -> list<__iterator_value_type<_InputIterator>, _Alloc>;
+list(_InputIterator, _InputIterator) -> list<__iter_value_t<_InputIterator>, _Alloc>;
 
 template <class _InputIterator,
           class _Alloc,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class = enable_if_t<__is_allocator_v<_Alloc>>>
-list(_InputIterator, _InputIterator, _Alloc) -> list<__iterator_value_type<_InputIterator>, _Alloc>;
+list(_InputIterator, _InputIterator, _Alloc) -> list<__iter_value_t<_InputIterator>, _Alloc>;
 #  endif
 
 #  if _LIBCPP_STD_VER >= 23
diff --git a/libcxx/include/queue b/libcxx/include/queue
index b4b79fb25a35f..28ba34f40d169 100644
--- a/libcxx/include/queue
+++ b/libcxx/include/queue
@@ -449,7 +449,7 @@ queue(_Container, _Alloc) -> queue<typename _Container::value_type, _Container>;
 
 #  if _LIBCPP_STD_VER >= 23
 template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0>
-queue(_InputIterator, _InputIterator) -> queue<__iterator_value_type<_InputIterator>>;
+queue(_InputIterator, _InputIterator) -> queue<__iter_value_t<_InputIterator>>;
 
 template <ranges::input_range _Range>
 queue(from_range_t, _Range&&) -> queue<ranges::range_value_t<_Range>>;
@@ -459,7 +459,7 @@ template <class _InputIterator,
           __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0,
           __enable_if_t<__is_allocator_v<_Alloc>, int>                             = 0>
 queue(_InputIterator, _InputIterator, _Alloc)
-    -> queue<__iterator_value_type<_InputIterator>, deque<__iterator_value_type<_InputIterator>, _Alloc>>;
+    -> queue<__iter_value_t<_InputIterator>, deque<__iter_value_t<_InputIterator>, _Alloc>>;
 
 template <ranges::input_range _Range, class _Alloc, __enable_if_t<__is_allocator_v<_Alloc>, int> = 0>
 queue(from_range_t, _Range&&, _Alloc)
@@ -705,13 +705,13 @@ template <class _Compare,
 priority_queue(_Compare, _Container) -> priority_queue<typename _Container::value_type, _Container, _Compare>;
 
 template <class _InputIterator,
-          class _Compare   = less<__iterator_value_type<_InputIterator>>,
-          class _Container = vector<__iterator_value_type<_InputIterator>>,
+          class _Compare   = less<__iter_value_t<_InputIterator>>,
+          class _Container = vector<__iter_value_t<_InputIterator>>,
           class            = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class            = enable_if_t<!__is_allocator_v<_Compare>>,
           class            = enable_if_t<!__is_allocator_v<_Container>>>
 priority_queue(_InputIterator, _InputIterator, _Compare = _Compare(), _Container = _Container())
-    -> priority_queue<__iterator_value_type<_InputIterator>, _Container, _Compare>;
+    -> priority_queue<__iter_value_t<_InputIterator>, _Container, _Compare>;
 
 template <class _Compare,
           class _Container,
@@ -726,9 +726,9 @@ template <class _InputIterator,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 priority_queue(_InputIterator, _InputIterator, _Allocator)
-    -> priority_queue<__iterator_value_type<_InputIterator>,
-                      vector<__iterator_value_type<_InputIterator>, _Allocator>,
-                      less<__iterator_value_type<_InputIterator>>>;
+    -> priority_queue<__iter_value_t<_InputIterator>,
+                      vector<__iter_value_t<_InputIterator>, _Allocator>,
+                      less<__iter_value_t<_InputIterator>>>;
 
 template <class _InputIterator,
           class _Compare,
@@ -737,9 +737,7 @@ template <class _InputIterator,
           class = enable_if_t<!__is_allocator_v<_Compare>>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 priority_queue(_InputIterator, _InputIterator, _Compare, _Allocator)
-    -> priority_queue<__iterator_value_type<_InputIterator>,
-                      vector<__iterator_value_type<_InputIterator>, _Allocator>,
-                      _Compare>;
+    -> priority_queue<__iter_value_t<_InputIterator>, vector<__iter_value_t<_InputIterator>, _Allocator>, _Compare>;
 
 template <class _InputIterator,
           class _Compare,
diff --git a/libcxx/include/set b/libcxx/include/set
index 59ed0155c1def..c1f7a0d477c3d 100644
--- a/libcxx/include/set
+++ b/libcxx/include/set
@@ -906,13 +906,13 @@ public:
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Compare   = less<__iterator_value_type<_InputIterator>>,
-          class _Allocator = allocator<__iterator_value_type<_InputIterator>>,
+          class _Compare   = less<__iter_value_t<_InputIterator>>,
+          class _Allocator = allocator<__iter_value_t<_InputIterator>>,
           class            = enable_if_t<__has_input_iterator_category<_InputIterator>::value, void>,
           class            = enable_if_t<__is_allocator_v<_Allocator>>,
           class            = enable_if_t<!__is_allocator_v<_Compare>>>
 set(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
-    -> set<__iterator_value_type<_InputIterator>, _Compare, _Allocator>;
+    -> set<__iter_value_t<_InputIterator>, _Compare, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 template <ranges::input_range _Range,
@@ -936,7 +936,7 @@ template <class _InputIterator,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value, void>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 set(_InputIterator, _InputIterator, _Allocator)
-    -> set<__iterator_value_type<_InputIterator>, less<__iterator_value_type<_InputIterator>>, _Allocator>;
+    -> set<__iter_value_t<_InputIterator>, less<__iter_value_t<_InputIterator>>, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 template <ranges::input_range _Range, class _Allocator, class = enable_if_t<__is_allocator_v<_Allocator>>>
@@ -1366,13 +1366,13 @@ public:
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Compare   = less<__iterator_value_type<_InputIterator>>,
-          class _Allocator = allocator<__iterator_value_type<_InputIterator>>,
+          class _Compare   = less<__iter_value_t<_InputIterator>>,
+          class _Allocator = allocator<__iter_value_t<_InputIterator>>,
           class            = enable_if_t<__has_input_iterator_category<_InputIterator>::value, void>,
           class            = enable_if_t<__is_allocator_v<_Allocator>>,
           class            = enable_if_t<!__is_allocator_v<_Compare>>>
 multiset(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
-    -> multiset<__iterator_value_type<_InputIterator>, _Compare, _Allocator>;
+    -> multiset<__iter_value_t<_InputIterator>, _Compare, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 template <ranges::input_range _Range,
@@ -1397,7 +1397,7 @@ template <class _InputIterator,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value, void>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 multiset(_InputIterator, _InputIterator, _Allocator)
-    -> multiset<__iterator_value_type<_InputIterator>, less<__iterator_value_type<_InputIterator>>, _Allocator>;
+    -> multiset<__iter_value_t<_InputIterator>, less<__iter_value_t<_InputIterator>>, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 template <ranges::input_range _Range, class _Allocator, class = enable_if_t<__is_allocator_v<_Allocator>>>
diff --git a/libcxx/include/stack b/libcxx/include/stack
index a2f285c1994b9..abf0ad8015656 100644
--- a/libcxx/include/stack
+++ b/libcxx/include/stack
@@ -306,7 +306,7 @@ stack(_Container, _Alloc) -> stack<typename _Container::value_type, _Container>;
 
 #  if _LIBCPP_STD_VER >= 23
 template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0>
-stack(_InputIterator, _InputIterator) -> stack<__iterator_value_type<_InputIterator>>;
+stack(_InputIterator, _InputIterator) -> stack<__iter_value_t<_InputIterator>>;
 
 template <ranges::input_range _Range>
 stack(from_range_t, _Range&&) -> stack<ranges::range_value_t<_Range>>;
@@ -316,7 +316,7 @@ template <class _InputIterator,
           __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0,
           __enable_if_t<__is_allocator_v<_Alloc>, int>                             = 0>
 stack(_InputIterator, _InputIterator, _Alloc)
-    -> stack<__iterator_value_type<_InputIterator>, deque<__iterator_value_type<_InputIterator>, _Alloc>>;
+    -> stack<__iter_value_t<_InputIterator>, deque<__iter_value_t<_InputIterator>, _Alloc>>;
 
 template <ranges::input_range _Range, class _Alloc, __enable_if_t<__is_allocator_v<_Alloc>, int> = 0>
 stack(from_range_t, _Range&&, _Alloc)
diff --git a/libcxx/include/string b/libcxx/include/string
index f5e05d885b6c5..351c5bfde53f1 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -2586,7 +2586,7 @@ inline const bool __is_transparently_comparable_v<_Comparator,
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _CharT     = __iterator_value_type<_InputIterator>,
+          class _CharT     = __iter_value_t<_InputIterator>,
           class _Allocator = allocator<_CharT>,
           class            = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class            = enable_if_t<__is_allocator_v<_Allocator>>>
diff --git a/libcxx/include/unordered_set b/libcxx/include/unordered_set
index 4d0e2ac21e125..6cb6f11388d6f 100644
--- a/libcxx/include/unordered_set
+++ b/libcxx/include/unordered_set
@@ -913,9 +913,9 @@ public:
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Hash      = hash<__iterator_value_type<_InputIterator>>,
-          class _Pred      = equal_to<__iterator_value_type<_InputIterator>>,
-          class _Allocator = allocator<__iterator_value_type<_InputIterator>>,
+          class _Hash      = hash<__iter_value_t<_InputIterator>>,
+          class _Pred      = equal_to<__iter_value_t<_InputIterator>>,
+          class _Allocator = allocator<__iter_value_t<_InputIterator>>,
           class            = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class            = enable_if_t<!__is_allocator_v<_Hash>>,
           class            = enable_if_t<!is_integral<_Hash>::value>,
@@ -926,8 +926,7 @@ unordered_set(_InputIterator,
               typename allocator_traits<_Allocator>::size_type = 0,
               _Hash                                            = _Hash(),
               _Pred                                            = _Pred(),
-              _Allocator                                       = _Allocator())
-    -> unordered_set<__iterator_value_type<_InputIterator>, _Hash, _Pred, _Allocator>;
+              _Allocator = _Allocator()) -> unordered_set<__iter_value_t<_InputIterator>, _Hash, _Pred, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 template <ranges::input_range _Range,
@@ -966,9 +965,9 @@ template <class _InputIterator,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 unordered_set(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Allocator)
-    -> unordered_set<__iterator_value_type<_InputIterator>,
-                     hash<__iterator_value_type<_InputIterator>>,
-                     equal_to<__iterator_value_type<_InputIterator>>,
+    -> unordered_set<__iter_value_t<_InputIterator>,
+                     hash<__iter_value_t<_InputIterator>>,
+                     equal_to<__iter_value_t<_InputIterator>>,
                      _Allocator>;
 
 template <class _InputIterator,
@@ -979,10 +978,7 @@ template <class _InputIterator,
           class = enable_if_t<!is_integral<_Hash>::value>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 unordered_set(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
-    -> unordered_set<__iterator_value_type<_InputIterator>,
-                     _Hash,
-                     equal_to<__iterator_value_type<_InputIterator>>,
-                     _Allocator>;
+    -> unordered_set<__iter_value_t<_InputIterator>, _Hash, equal_to<__iter_value_t<_InputIterator>>, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 
@@ -1502,9 +1498,9 @@ public:
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
-          class _Hash      = hash<__iterator_value_type<_InputIterator>>,
-          class _Pred      = equal_to<__iterator_value_type<_InputIterator>>,
-          class _Allocator = allocator<__iterator_value_type<_InputIterator>>,
+          class _Hash      = hash<__iter_value_t<_InputIterator>>,
+          class _Pred      = equal_to<__iter_value_t<_InputIterator>>,
+          class _Allocator = allocator<__iter_value_t<_InputIterator>>,
           class            = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class            = enable_if_t<!__is_allocator_v<_Hash>>,
           class            = enable_if_t<!is_integral<_Hash>::value>,
@@ -1516,7 +1512,7 @@ unordered_multiset(
     typename allocator_traits<_Allocator>::size_type = 0,
     _Hash                                            = _Hash(),
     _Pred                                            = _Pred(),
-    _Allocator = _Allocator()) -> unordered_multiset<__iterator_value_type<_InputIterator>, _Hash, _Pred, _Allocator>;
+    _Allocator = _Allocator()) -> unordered_multiset<__iter_value_t<_InputIterator>, _Hash, _Pred, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 template <ranges::input_range _Range,
@@ -1555,9 +1551,9 @@ template <class _InputIterator,
           class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 unordered_multiset(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Allocator)
-    -> unordered_multiset<__iterator_value_type<_InputIterator>,
-                          hash<__iterator_value_type<_InputIterator>>,
-                          equal_to<__iterator_value_type<_InputIterator>>,
+    -> unordered_multiset<__iter_value_t<_InputIterator>,
+                          hash<__iter_value_t<_InputIterator>>,
+                          equal_to<__iter_value_t<_InputIterator>>,
                           _Allocator>;
 
 template <class _InputIterator,
@@ -1568,10 +1564,7 @@ template <class _InputIterator,
           class = enable_if_t<!is_integral<_Hash>::value>,
           class = enable_if_t<__is_allocator_v<_Allocator>>>
 unordered_multiset(_InputIterator, _InputIterator, typename allocator_traits<_Allocator>::size_type, _Hash, _Allocator)
-    -> unordered_multiset<__iterator_value_type<_InputIterator>,
-                          _Hash,
-                          equal_to<__iterator_value_type<_InputIterator>>,
-                          _Allocator>;
+    -> unordered_multiset<__iter_value_t<_InputIterator>, _Hash, equal_to<__iter_value_t<_InputIterator>>, _Allocator>;
 
 #    if _LIBCPP_STD_VER >= 23
 
diff --git a/libcxx/test/libcxx/algorithms/cpp17_iterator_concepts.verify.cpp b/libcxx/test/libcxx/algorithms/cpp17_iterator_concepts.verify.cpp
index ed7584f0468b7..05de83a03d820 100644
--- a/libcxx/test/libcxx/algorithms/cpp17_iterator_concepts.verify.cpp
+++ b/libcxx/test/libcxx/algorithms/cpp17_iterator_concepts.verify.cpp
@@ -102,7 +102,7 @@ void check_iterator_requirements() {
   // expected-note@*:* {{because 'not_copy_assignable' does not satisfy '__cpp17_copy_assignable'}}
 
   static_assert(std::__cpp17_iterator<diff_t_not_signed>); // expected-error {{static assertion failed}}
-  // expected-note-re@*:* {{because 'is_signed_v<__iterator_difference_type<diff_t_not_signed>{{.*}}>' evaluated to false}}
+  // expected-note-re@*:* {{because 'is_signed_v<__iter_difference_t<diff_t_not_signed>{{.*}}>' evaluated to false}}
 }
 
 struct not_equality_comparable : valid_iterator<not_equality_comparable> {};
@@ -173,7 +173,7 @@ void check_bidirectional_iterator_requirements() {
   _LIBCPP_REQUIRE_CPP17_BIDIRECTIONAL_ITERATOR(missing_postdecrement, ""); // expected-error {{static assertion failed}}
   // expected-note@*:* {{cannot decrement value of type 'missing_postdecrement'}}
   _LIBCPP_REQUIRE_CPP17_BIDIRECTIONAL_ITERATOR(not_returning_iter_reference, ""); // expected-error {{static assertion failed}}
-  // expected-note-re@*:* {{'same_as<int, __iterator_reference<not_returning_iter_reference>{{ ?}}>'}}
+  // expected-note-re@*:* {{'same_as<int, __iter_reference_t<not_returning_iter_reference>{{ ?}}>'}}
   // clang-format on
 }