diff --git a/libcxx/docs/Status/RangesPaper.csv b/libcxx/docs/Status/RangesPaper.csv
--- a/libcxx/docs/Status/RangesPaper.csv
+++ b/libcxx/docs/Status/RangesPaper.csv
@@ -17,7 +17,7 @@
| *no-throw-input-range*
| *no-throw-forward-iterator*
| *no-throw-forward-range*","| [iterator.concepts]
-| [range.refinements]",Konstantin Varlamov,Not started
+| [range.refinements]",Konstantin Varlamov,✅
`[specialized.algorithms] <http://wg21.link/specialized.algorithms>`_,"| ranges::uninitialized_default_construct
| ranges::uninitialized_default_construct_n
| ranges::uninitialized_value_construct
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -228,6 +228,7 @@
__memory/allocator.h
__memory/auto_ptr.h
__memory/compressed_pair.h
+ __memory/concepts.h
__memory/construct_at.h
__memory/pointer_traits.h
__memory/raw_storage_iterator.h
diff --git a/libcxx/include/__memory/concepts.h b/libcxx/include/__memory/concepts.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__memory/concepts.h
@@ -0,0 +1,63 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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___MEMORY_CONCEPTS_H
+#define _LIBCPP___MEMORY_CONCEPTS_H
+
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+namespace ranges {
+
+// [special.mem.concepts]
+
+// This concept ensures that uninitialized algorithms can construct an object
+// at the address pointed-to by the iterator, which requires an lvalue.
+template <class _Ip>
+concept __nothrow_input_iterator =
+ input_iterator<_Ip> &&
+ is_lvalue_reference_v<iter_reference_t<_Ip>> &&
+ same_as<remove_cvref_t<iter_reference_t<_Ip>>, iter_value_t<_Ip>>;
+
+template <class _Sp, class _Ip>
+concept __nothrow_sentinel_for = sentinel_for<_Sp, _Ip>;
+
+template <class _Rp>
+concept __nothrow_input_range =
+ range<_Rp> &&
+ __nothrow_input_iterator<iterator_t<_Rp>> &&
+ __nothrow_sentinel_for<sentinel_t<_Rp>, iterator_t<_Rp>>;
+
+template <class _Ip>
+concept __nothrow_forward_iterator =
+ __nothrow_input_iterator<_Ip> &&
+ forward_iterator<_Ip> &&
+ __nothrow_sentinel_for<_Ip, _Ip>;
+
+template <class _Rp>
+concept __nothrow_forward_range =
+ __nothrow_input_range<_Rp> &&
+ __nothrow_forward_iterator<iterator_t<_Rp>>;
+
+} // namespace ranges
+#endif // !defined(_LIBCPP_HAS_NO_RANGES)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___MEMORY_CONCEPTS_H
diff --git a/libcxx/include/memory b/libcxx/include/memory
--- a/libcxx/include/memory
+++ b/libcxx/include/memory
@@ -669,6 +669,7 @@
#include <__memory/allocator_arg_t.h>
#include <__memory/allocator_traits.h>
#include <__memory/compressed_pair.h>
+#include <__memory/concepts.h>
#include <__memory/construct_at.h>
#include <__memory/pointer_traits.h>
#include <__memory/raw_storage_iterator.h>
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -630,21 +630,22 @@
export *
module __memory {
- module addressof { private header "__memory/addressof.h" }
- module allocation_guard { private header "__memory/allocation_guard.h" }
- module allocator { private header "__memory/allocator.h" }
- module allocator_arg_t { private header "__memory/allocator_arg_t.h" }
- module allocator_traits { private header "__memory/allocator_traits.h" }
- module auto_ptr { private header "__memory/auto_ptr.h" }
- module compressed_pair { private header "__memory/compressed_pair.h" }
- module construct_at { private header "__memory/construct_at.h" }
- module pointer_traits { private header "__memory/pointer_traits.h" }
- module raw_storage_iterator { private header "__memory/raw_storage_iterator.h" }
- module shared_ptr { private header "__memory/shared_ptr.h" }
- module temporary_buffer { private header "__memory/temporary_buffer.h" }
- module uninitialized_algorithms { private header "__memory/uninitialized_algorithms.h" }
- module unique_ptr { private header "__memory/unique_ptr.h" }
- module uses_allocator { private header "__memory/uses_allocator.h" }
+ module addressof { private header "__memory/addressof.h" }
+ module allocation_guard { private header "__memory/allocation_guard.h" }
+ module allocator { private header "__memory/allocator.h" }
+ module allocator_arg_t { private header "__memory/allocator_arg_t.h" }
+ module allocator_traits { private header "__memory/allocator_traits.h" }
+ module auto_ptr { private header "__memory/auto_ptr.h" }
+ module compressed_pair { private header "__memory/compressed_pair.h" }
+ module concepts { private header "__memory/concepts.h" }
+ module construct_at { private header "__memory/construct_at.h" }
+ module pointer_traits { private header "__memory/pointer_traits.h" }
+ module raw_storage_iterator { private header "__memory/raw_storage_iterator.h" }
+ module shared_ptr { private header "__memory/shared_ptr.h" }
+ module temporary_buffer { private header "__memory/temporary_buffer.h" }
+ module uninitialized_algorithms { private header "__memory/uninitialized_algorithms.h" }
+ module unique_ptr { private header "__memory/unique_ptr.h" }
+ module uses_allocator { private header "__memory/uses_allocator.h" }
}
}
module mutex {
diff --git a/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_forward_iterator.compile.pass.cpp b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_forward_iterator.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_forward_iterator.compile.pass.cpp
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// template<class I>
+// concept __nothrow_forward_iterator;
+
+#include <memory>
+
+#include "test_iterators.h"
+
+struct ForwardProxyIterator {
+ using value_type = int;
+ using difference_type = int;
+ ForwardProxyIterator& operator++();
+ ForwardProxyIterator operator++(int);
+ bool operator==(const ForwardProxyIterator&) const;
+
+ int operator*() const;
+};
+
+static_assert(std::ranges::__nothrow_forward_iterator<forward_iterator<int*>>);
+static_assert(std::forward_iterator<ForwardProxyIterator>);
+static_assert(!std::ranges::__nothrow_forward_iterator<ForwardProxyIterator>);
diff --git a/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_forward_range.compile.pass.cpp b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_forward_range.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_forward_range.compile.pass.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// template<class R>
+// concept __nothrow_forward_range;
+
+#include <memory>
+
+#include "test_iterators.h"
+#include "test_range.h"
+
+// Has to be a template to work with `test_range`.
+template <typename>
+struct ForwardProxyIterator {
+ using value_type = int;
+ using difference_type = int;
+ ForwardProxyIterator& operator++();
+ ForwardProxyIterator operator++(int);
+ bool operator==(const ForwardProxyIterator&) const;
+
+ int operator*() const;
+};
+
+static_assert(std::ranges::__nothrow_forward_range<test_range<forward_iterator>>);
+static_assert(!std::ranges::__nothrow_forward_range<test_range<cpp20_input_iterator>>);
+static_assert(std::ranges::forward_range<test_range<ForwardProxyIterator>>);
+static_assert(!std::ranges::__nothrow_forward_range<test_range<ForwardProxyIterator>>);
diff --git a/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_input_iterator.compile.pass.cpp b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_input_iterator.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_input_iterator.compile.pass.cpp
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// template<class I>
+// concept __nothrow_input_iterator;
+
+#include <memory>
+
+#include "test_iterators.h"
+
+struct InputProxyIterator {
+ using value_type = int;
+ using difference_type = int;
+ InputProxyIterator& operator++();
+ InputProxyIterator operator++(int);
+
+ int operator*() const;
+};
+
+static_assert(std::ranges::__nothrow_input_iterator<cpp20_input_iterator<int*>>);
+static_assert(!std::ranges::__nothrow_input_iterator<output_iterator<int*>>);
+static_assert(std::input_iterator<InputProxyIterator>);
+static_assert(!std::ranges::__nothrow_input_iterator<InputProxyIterator>);
diff --git a/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_input_range.compile.pass.cpp b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_input_range.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_input_range.compile.pass.cpp
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// template<class R>
+// concept __nothrow_input_range;
+
+#include <memory>
+
+#include "test_iterators.h"
+#include "test_range.h"
+
+// Has to be a template to work with `test_range`.
+template <typename>
+struct InputProxyIterator {
+ using value_type = int;
+ using difference_type = int;
+ InputProxyIterator& operator++();
+ InputProxyIterator operator++(int);
+
+ int operator*() const;
+};
+
+static_assert(std::ranges::__nothrow_input_range<test_range<cpp20_input_iterator>>);
+static_assert(std::ranges::input_range<test_range<InputProxyIterator>>);
+static_assert(!std::ranges::__nothrow_input_range<test_range<InputProxyIterator>>);
diff --git a/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_sentinel_for.compile.pass.cpp b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_sentinel_for.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/algorithms/specialized.algorithms/special.mem.concepts/nothrow_sentinel_for.compile.pass.cpp
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// template<class S, class I>
+// concept __nothrow_sentinel_for;
+
+#include <memory>
+
+static_assert(std::ranges::__nothrow_sentinel_for<int*, int*>);
+static_assert(!std::ranges::__nothrow_sentinel_for<int*, long*>);