[libc++] Implement P0429R9 std::flat_map (#98643)

Around half of the tests are based on the tests Arthur O'Dwyer's
original implementation of std::flat_map, with modifications and
removals.

partially implement #105190

libcxx/docs/ReleaseNotes/20.rst

@@ -43,6 +43,7 @@ Implemented Papers
 - P2985R0: A type trait for detecting virtual base classes (`Github <https://github.com/llvm/llvm-project/issues/105432>`__)
 - ``std::jthread`` and ``<stop_token>`` are not guarded behind ``-fexperimental-library`` anymore
 - P2674R1: A trait for implicit lifetime types (`Github <https://github.com/llvm/llvm-project/issues/105259>`__)
+- P0429R9: A Standard ``flat_map`` is partially implemented and ``flat_map`` is provided (`Github <https://github.com/llvm/llvm-project/issues/105190>`__)
 
 Improvements and New Features
 -----------------------------

libcxx/docs/Status/Cxx23Papers.csv

@@ -52,7 +52,7 @@
 "`P2443R1 <https://wg21.link/P2443R1>`__","``views::chunk_by``","2022-02 (Virtual)","|Complete|","18.0",""
 "","","","","",""
 "`P0009R18 <https://wg21.link/P0009R18>`__","mdspan: A Non-Owning Multidimensional Array Reference","2022-07 (Virtual)","|Complete|","18.0",""
-"`P0429R9 <https://wg21.link/P0429R9>`__","A Standard ``flat_map``","2022-07 (Virtual)","","",""
+"`P0429R9 <https://wg21.link/P0429R9>`__","A Standard ``flat_map``","2022-07 (Virtual)","|In progress|","",""
 "`P1169R4 <https://wg21.link/P1169R4>`__","``static operator()``","2022-07 (Virtual)","|Complete|","16.0",""
 "`P1222R4 <https://wg21.link/P1222R4>`__","A Standard ``flat_set``","2022-07 (Virtual)","","",""
 "`P1223R5 <https://wg21.link/P1223R5>`__","``ranges::find_last()``, ``ranges::find_last_if()``, and ``ranges::find_last_if_not()``","2022-07 (Virtual)","|Complete|","19.0",""

libcxx/include/CMakeLists.txt

@@ -358,6 +358,8 @@ set(files
   __filesystem/recursive_directory_iterator.h
   __filesystem/space_info.h
   __filesystem/u8path.h
+  __flat_map/flat_map.h
+  __flat_map/sorted_unique.h
   __format/buffer.h
   __format/concepts.h
   __format/container_adaptor.h
@@ -959,6 +961,7 @@ set(files
   ext/hash_set
   fenv.h
   filesystem
+  flat_map
   float.h
   format
   forward_list

libcxx/include/__flat_map/sorted_unique.h

@@ -0,0 +1,31 @@
+// -*- 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___FLAT_MAP_SORTED_UNIQUE_H
+#define _LIBCPP___FLAT_MAP_SORTED_UNIQUE_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 23
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct sorted_unique_t {
+  explicit sorted_unique_t() = default;
+};
+inline constexpr sorted_unique_t sorted_unique{};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 23
+
+#endif // _LIBCPP___FLAT_MAP_SORTED_UNIQUE_H

libcxx/include/__utility/exception_guard.h

@@ -137,6 +137,12 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __exception_guard<_Rollback> __make_exce
   return __exception_guard<_Rollback>(std::move(__rollback));
 }
 
+template <class _Rollback>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __exception_guard_exceptions<_Rollback>
+__make_scope_guard(_Rollback __rollback) {
+  return __exception_guard_exceptions<_Rollback>(std::move(__rollback));
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

libcxx/include/flat_map

@@ -0,0 +1,54 @@
+// -*- 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_FLAT_MAP
+#define _LIBCPP_FLAT_MAP
+
+/*
+  Header <flat_map> synopsis
+
+#include <compare>              // see [compare.syn]
+#include <initializer_list>     // see [initializer.list.syn]
+
+namespace std {
+  // [flat.map], class template flat_map
+  template<class Key, class T, class Compare = less<Key>,
+           class KeyContainer = vector<Key>, class MappedContainer = vector<T>>
+    class flat_map;
+
+  struct sorted_unique_t { explicit sorted_unique_t() = default; };
+  inline constexpr sorted_unique_t sorted_unique{};
+
+  template<class Key, class T, class Compare, class KeyContainer, class MappedContainer,
+           class Allocator>
+    struct uses_allocator<flat_map<Key, T, Compare, KeyContainer, MappedContainer>,
+                          Allocator>;
+
+  // [flat.map.erasure], erasure for flat_map
+  template<class Key, class T, class Compare, class KeyContainer, class MappedContainer,
+           class Predicate>
+    typename flat_map<Key, T, Compare, KeyContainer, MappedContainer>::size_type
+      erase_if(flat_map<Key, T, Compare, KeyContainer, MappedContainer>& c, Predicate pred);
+*/
+
+#include <__assert> // all public C++ headers provide the assertion handler
+#include <__config>
+#include <__flat_map/flat_map.h>
+#include <__flat_map/sorted_unique.h>
+#include <version>
+
+// standard required includes
+#include <compare>
+#include <initializer_list>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#endif // _LIBCPP_FLAT_MAP

libcxx/include/module.modulemap

@@ -1222,6 +1222,14 @@ module std [system] {
     export *
   }
 
+  module flat_map {
+    module flat_map                       { header "__flat_map/flat_map.h" }
+    module sorted_unique                  { header "__flat_map/sorted_unique.h" }
+
+    header "flat_map"
+    export *
+  }
+  
   module format {
     module buffer                             { header "__format/buffer.h" }
     module concepts                           { header "__format/concepts.h" }

libcxx/modules/std.compat.cppm.in

@@ -53,9 +53,6 @@ module;
 #  if __has_include(<debugging>)
 #    error "please update the header information for <debugging> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<debugging>)
-#  if __has_include(<flat_map>)
-#    error "please update the header information for <flat_map> in headers_not_available in utils/libcxx/header_information.py"
-#  endif // __has_include(<flat_map>)
 #  if __has_include(<flat_set>)
 #    error "please update the header information for <flat_set> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<flat_set>)

libcxx/modules/std.cppm.in

@@ -64,6 +64,7 @@ module;
 #include <execution>
 #include <expected>
 #include <filesystem>
+#include <flat_map>
 #include <format>
 #include <forward_list>
 #if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
@@ -161,9 +162,6 @@ module;
 #  if __has_include(<debugging>)
 #    error "please update the header information for <debugging> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<debugging>)
-#  if __has_include(<flat_map>)
-#    error "please update the header information for <flat_map> in headers_not_available in utils/libcxx/header_information.py"
-#  endif // __has_include(<flat_map>)
 #  if __has_include(<flat_set>)
 #    error "please update the header information for <flat_set> in headers_not_available in utils/libcxx/header_information.py"
 #  endif // __has_include(<flat_set>)

libcxx/modules/std/flat_map.inc

@@ -8,8 +8,8 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
-#if 0
-  // [flat.map], class template flat_­map
+#if _LIBCPP_STD_VER >= 23
+  // [flat.map], class template flat_map
   using std::flat_map;
 
   using std::sorted_unique;
@@ -17,15 +17,17 @@ export namespace std {
 
   using std::uses_allocator;
 
-  // [flat.map.erasure], erasure for flat_­map
+  // [flat.map.erasure], erasure for flat_map
   using std::erase_if;
 
-  // [flat.multimap], class template flat_­multimap
+#endif // _LIBCPP_STD_VER >= 23
+#if 0
+  // [flat.multimap], class template flat_multimap
   using std::flat_multimap;
 
   using std::sorted_equivalent;
   using std::sorted_equivalent_t;
 
-  // [flat.multimap.erasure], erasure for flat_­multimap
+  // [flat.multimap.erasure], erasure for flat_multimap
 #endif
 } // namespace std

libcxx/test/libcxx/containers/containers.adaptors/flat.map/assert.input_range.pass.cpp

@@ -0,0 +1,66 @@
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: has-unix-headers
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: libcpp-hardening-mode=none
+// XFAIL: libcpp-hardening-mode=debug && availability-verbose_abort-missing
+
+// <flat_map>
+
+// flat_map(key_container_type , mapped_container_type , const key_compare& __comp = key_compare())
+// flat_map(const key_container_type& , const mapped_container_type& , const _Allocator& )
+// flat_map(const key_container_type& , const mapped_container_type& , const key_compare&, const _Allocator& )
+// void replace(key_container_type&& , mapped_container_type&&)
+//
+
+#include <flat_map>
+#include <functional>
+#include <memory>
+#include <vector>
+
+#include "check_assertion.h"
+
+int main(int, char**) {
+  using M = std::flat_map<int, int>;
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] { M m({1, 2, 3}, {4}); }()), "flat_map keys and mapped containers have different size");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] { M m({1, 2, 3}, {4}, std::less<int>{}); }()), "flat_map keys and mapped containers have different size");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector keys{1, 2, 3};
+        const std::vector values{4};
+        const std::allocator<int> alloc{};
+        M m(keys, values, alloc);
+      }()),
+      "flat_map keys and mapped containers have different size");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector keys{1, 2, 3};
+        const std::vector values{4};
+        const std::less<int> key_compare{};
+        const std::allocator<int> alloc{};
+        M m(keys, values, key_compare, alloc);
+      }()),
+      "flat_map keys and mapped containers have different size");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::vector keys{1, 2, 3};
+        std::vector values{4};
+        M m;
+        m.replace(std::move(keys), std::move(values));
+      }()),
+      "flat_map keys and mapped containers have different size");
+
+  return 0;
+}

libcxx/test/libcxx/containers/containers.adaptors/flat.map/assert.sorted_unique.pass.cpp

@@ -0,0 +1,225 @@
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: has-unix-headers
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: libcpp-hardening-mode=none
+// REQUIRES: libcpp-hardening-mode=debug
+// XFAIL: libcpp-hardening-mode=debug && availability-verbose_abort-missing
+
+// <flat_map>
+
+// flat_map(key_container_type , mapped_container_type , const key_compare& __comp = key_compare())
+// flat_map(const key_container_type& , const mapped_container_type& , const _Allocator& )
+// flat_map(const key_container_type& , const mapped_container_type& , const key_compare&, const _Allocator& )
+// void replace(key_container_type&& , mapped_container_type&&)
+//
+
+#include <flat_map>
+#include <functional>
+#include <initializer_list>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "check_assertion.h"
+
+int main(int, char**) {
+  using M = std::flat_map<int, int>;
+
+  TEST_LIBCPP_ASSERT_FAILURE(([] { M m(std::sorted_unique, {2, 2, 3}, {4, 5, 6}); }()),
+                             "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(([] { M m(std::sorted_unique, {4, 2, 3}, {4, 5, 6}); }()),
+                             "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(([] { M m(std::sorted_unique, {2, 2, 3}, {4, 5, 6}, std::less<int>{}); }()),
+                             "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(([] { M m(std::sorted_unique, {4, 2, 3}, {4, 5, 6}, std::less<int>{}); }()),
+                             "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector keys{2, 2, 3};
+        const std::vector values{4, 5, 6};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, keys, values, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector keys{4, 2, 3};
+        const std::vector values{4, 5, 6};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, keys, values, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector keys{2, 2, 3};
+        const std::vector values{4, 5, 6};
+        const std::allocator<int> alloc{};
+        const std::less<int> comp{};
+        M m(std::sorted_unique, keys, values, comp, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector keys{4, 2, 3};
+        const std::vector values{4, 5, 6};
+        const std::allocator<int> alloc{};
+        const std::less<int> comp{};
+        M m(std::sorted_unique, keys, values, comp, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        M m(std::sorted_unique, v.begin(), v.end(), comp);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        M m(std::sorted_unique, v.begin(), v.end(), comp);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v.begin(), v.end(), comp, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v.begin(), v.end(), comp, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v.begin(), v.end(), alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v.begin(), v.end(), alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        M m(std::sorted_unique, v, comp);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        M m(std::sorted_unique, v, comp);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v, comp, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        const std::less<int> comp{};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v, comp, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        const std::allocator<int> alloc{};
+        M m(std::sorted_unique, v, alloc);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        M m;
+        m.insert(std::sorted_unique, v.begin(), v.end());
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        const std::vector<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        M m;
+        m.insert(std::sorted_unique, v.begin(), v.end());
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{2, 4}, {2, 5}, {3, 6}};
+        M m;
+        m.insert(std::sorted_unique, v);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::initializer_list<std::pair<int, int>> v{{4, 4}, {2, 5}, {3, 6}};
+        M m;
+        m.insert(std::sorted_unique, v);
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+
+  TEST_LIBCPP_ASSERT_FAILURE(
+      ([] {
+        std::vector keys{1, 1, 3};
+        std::vector values{4, 5, 6};
+        M m;
+        m.replace(std::move(keys), std::move(values));
+      }()),
+      "Either the key container is not sorted or it contains duplicates");
+  return 0;
+}

libcxx/test/libcxx/containers/containers.adaptors/flat.map/container_stability.pass.cpp

@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(key_container_type key_cont, mapped_container_type mapped_cont);
+//
+// libc++ uses stable_sort to ensure that flat_map's behavior matches map's,
+// in terms of which duplicate items are kept.
+// This tests a conforming extension.
+
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <flat_map>
+#include <random>
+#include <map>
+#include <vector>
+
+#include "test_macros.h"
+
+struct Mod256 {
+  bool operator()(int x, int y) const { return (x % 256) < (y % 256); }
+};
+
+int main(int, char**) {
+  std::mt19937 randomness;
+  std::vector<uint16_t> values;
+  std::vector<std::pair<uint16_t, uint16_t>> pairs;
+  for (int i = 0; i < 200; ++i) {
+    uint16_t r = randomness();
+    values.push_back(r);
+    pairs.emplace_back(r, r);
+  }
+
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs.begin(), pairs.end());
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(values, values);
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs.begin(), pairs.end());
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(values, values, Mod256());
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs.begin(), pairs.end());
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(values, values, std::allocator<int>());
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs.begin(), pairs.end());
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(values, values, Mod256(), std::allocator<int>());
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  return 0;
+}

libcxx/test/libcxx/transitive_includes/cxx03.csv

@@ -682,6 +682,50 @@ filesystem typeinfo
 filesystem utility
 filesystem variant
 filesystem version
+flat_map algorithm
+flat_map array
+flat_map atomic
+flat_map bit
+flat_map cctype
+flat_map cerrno
+flat_map climits
+flat_map clocale
+flat_map cmath
+flat_map compare
+flat_map concepts
+flat_map cstdarg
+flat_map cstddef
+flat_map cstdint
+flat_map cstdio
+flat_map cstdlib
+flat_map cstring
+flat_map ctime
+flat_map cwchar
+flat_map cwctype
+flat_map exception
+flat_map initializer_list
+flat_map ios
+flat_map iosfwd
+flat_map iterator
+flat_map limits
+flat_map locale
+flat_map memory
+flat_map mutex
+flat_map new
+flat_map optional
+flat_map ratio
+flat_map stdexcept
+flat_map streambuf
+flat_map string
+flat_map string_view
+flat_map system_error
+flat_map tuple
+flat_map type_traits
+flat_map typeinfo
+flat_map utility
+flat_map variant
+flat_map vector
+flat_map version
 format algorithm
 format array
 format atomic

libcxx/test/libcxx/transitive_includes/cxx11.csv

@@ -682,6 +682,50 @@ filesystem typeinfo
 filesystem utility
 filesystem variant
 filesystem version
+flat_map algorithm
+flat_map array
+flat_map atomic
+flat_map bit
+flat_map cctype
+flat_map cerrno
+flat_map climits
+flat_map clocale
+flat_map cmath
+flat_map compare
+flat_map concepts
+flat_map cstdarg
+flat_map cstddef
+flat_map cstdint
+flat_map cstdio
+flat_map cstdlib
+flat_map cstring
+flat_map ctime
+flat_map cwchar
+flat_map cwctype
+flat_map exception
+flat_map initializer_list
+flat_map ios
+flat_map iosfwd
+flat_map iterator
+flat_map limits
+flat_map locale
+flat_map memory
+flat_map mutex
+flat_map new
+flat_map optional
+flat_map ratio
+flat_map stdexcept
+flat_map streambuf
+flat_map string
+flat_map string_view
+flat_map system_error
+flat_map tuple
+flat_map type_traits
+flat_map typeinfo
+flat_map utility
+flat_map variant
+flat_map vector
+flat_map version
 format algorithm
 format array
 format atomic

libcxx/test/libcxx/transitive_includes/cxx14.csv

@@ -700,6 +700,51 @@ filesystem typeinfo
 filesystem utility
 filesystem variant
 filesystem version
+flat_map algorithm
+flat_map array
+flat_map atomic
+flat_map bit
+flat_map cctype
+flat_map cerrno
+flat_map climits
+flat_map clocale
+flat_map cmath
+flat_map compare
+flat_map concepts
+flat_map cstdarg
+flat_map cstddef
+flat_map cstdint
+flat_map cstdio
+flat_map cstdlib
+flat_map cstring
+flat_map ctime
+flat_map cwchar
+flat_map cwctype
+flat_map exception
+flat_map execution
+flat_map initializer_list
+flat_map ios
+flat_map iosfwd
+flat_map iterator
+flat_map limits
+flat_map locale
+flat_map memory
+flat_map mutex
+flat_map new
+flat_map optional
+flat_map ratio
+flat_map stdexcept
+flat_map streambuf
+flat_map string
+flat_map string_view
+flat_map system_error
+flat_map tuple
+flat_map type_traits
+flat_map typeinfo
+flat_map utility
+flat_map variant
+flat_map vector
+flat_map version
 format algorithm
 format array
 format atomic

libcxx/test/libcxx/transitive_includes/cxx17.csv

@@ -706,6 +706,50 @@ filesystem utility
 filesystem variant
 filesystem vector
 filesystem version
+flat_map algorithm
+flat_map array
+flat_map atomic
+flat_map bit
+flat_map cctype
+flat_map cerrno
+flat_map climits
+flat_map clocale
+flat_map cmath
+flat_map compare
+flat_map concepts
+flat_map cstdarg
+flat_map cstddef
+flat_map cstdint
+flat_map cstdio
+flat_map cstdlib
+flat_map cstring
+flat_map ctime
+flat_map cwchar
+flat_map cwctype
+flat_map exception
+flat_map initializer_list
+flat_map ios
+flat_map iosfwd
+flat_map iterator
+flat_map limits
+flat_map locale
+flat_map memory
+flat_map mutex
+flat_map new
+flat_map optional
+flat_map ratio
+flat_map stdexcept
+flat_map streambuf
+flat_map string
+flat_map string_view
+flat_map system_error
+flat_map tuple
+flat_map type_traits
+flat_map typeinfo
+flat_map utility
+flat_map variant
+flat_map vector
+flat_map version
 format algorithm
 format array
 format atomic

libcxx/test/libcxx/transitive_includes/cxx20.csv

@@ -694,6 +694,50 @@ filesystem utility
 filesystem variant
 filesystem vector
 filesystem version
+flat_map algorithm
+flat_map array
+flat_map atomic
+flat_map bit
+flat_map cctype
+flat_map cerrno
+flat_map climits
+flat_map clocale
+flat_map cmath
+flat_map compare
+flat_map concepts
+flat_map cstdarg
+flat_map cstddef
+flat_map cstdint
+flat_map cstdio
+flat_map cstdlib
+flat_map cstring
+flat_map ctime
+flat_map cwchar
+flat_map cwctype
+flat_map exception
+flat_map initializer_list
+flat_map ios
+flat_map iosfwd
+flat_map iterator
+flat_map limits
+flat_map locale
+flat_map memory
+flat_map mutex
+flat_map new
+flat_map optional
+flat_map ratio
+flat_map stdexcept
+flat_map streambuf
+flat_map string
+flat_map string_view
+flat_map system_error
+flat_map tuple
+flat_map type_traits
+flat_map typeinfo
+flat_map utility
+flat_map variant
+flat_map vector
+flat_map version
 format algorithm
 format array
 format atomic

libcxx/test/libcxx/transitive_includes/cxx23.csv

@@ -381,6 +381,31 @@ filesystem string_view
 filesystem tuple
 filesystem typeinfo
 filesystem version
+flat_map array
+flat_map cctype
+flat_map cerrno
+flat_map climits
+flat_map clocale
+flat_map compare
+flat_map cstddef
+flat_map cstdint
+flat_map cstdio
+flat_map cstdlib
+flat_map cstring
+flat_map cwchar
+flat_map cwctype
+flat_map initializer_list
+flat_map iosfwd
+flat_map limits
+flat_map new
+flat_map optional
+flat_map stdexcept
+flat_map string
+flat_map string_view
+flat_map tuple
+flat_map typeinfo
+flat_map vector
+flat_map version
 format array
 format cctype
 format cerrno

libcxx/test/libcxx/transitive_includes/cxx26.csv

@@ -381,6 +381,31 @@ filesystem string_view
 filesystem tuple
 filesystem typeinfo
 filesystem version
+flat_map array
+flat_map cctype
+flat_map cerrno
+flat_map climits
+flat_map clocale
+flat_map compare
+flat_map cstddef
+flat_map cstdint
+flat_map cstdio
+flat_map cstdlib
+flat_map cstring
+flat_map cwchar
+flat_map cwctype
+flat_map initializer_list
+flat_map iosfwd
+flat_map limits
+flat_map new
+flat_map optional
+flat_map stdexcept
+flat_map string
+flat_map string_view
+flat_map tuple
+flat_map typeinfo
+flat_map vector
+flat_map version
 format array
 format cctype
 format cerrno

libcxx/test/std/containers/container.adaptors/NaiveStaticVector.h

@@ -0,0 +1,94 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 SUPPORT_NAIVE_STATIC_VECTOR_H
+#define SUPPORT_NAIVE_STATIC_VECTOR_H
+
+#include <cstddef>
+#include <utility>
+#include "test_iterators.h"
+#include "test_macros.h"
+
+template <class T, std::size_t N>
+struct NaiveStaticVector {
+  struct CapacityError {};
+
+  using value_type      = T;
+  using difference_type = short;
+  using size_type       = unsigned short;
+  using iterator        = random_access_iterator<T*>;
+  using const_iterator  = random_access_iterator<const T*>;
+
+  explicit NaiveStaticVector() = default;
+  template <class It>
+  explicit NaiveStaticVector(It first, It last) {
+    while (first != last)
+      insert(*first++);
+  }
+
+  // Moving-from a NaiveStaticVector leaves the source vector holding moved-from objects.
+  // This is intentional (the "Naive" in the name).
+  // Specifically, moving-out-of a sorted+uniqued NaiveStaticVector<MoveOnly>
+  // will leave it in a non-sorted+uniqued state.
+
+  NaiveStaticVector(const NaiveStaticVector&)            = default;
+  NaiveStaticVector(NaiveStaticVector&&)                 = default; // deliberately don't reset size_
+  NaiveStaticVector& operator=(const NaiveStaticVector&) = default;
+  NaiveStaticVector& operator=(NaiveStaticVector&&)      = default;
+
+  iterator begin() { return iterator(data_); }
+  const_iterator begin() const { return const_iterator(data_); }
+  const_iterator cbegin() const { return const_iterator(data_); }
+  iterator end() { return begin() + size(); }
+  const_iterator end() const { return begin() + size(); }
+  size_type size() const { return size_; }
+  bool empty() const { return size_ == 0; }
+
+  void clear() { size_ = 0; }
+
+  template <class It>
+  iterator insert(const_iterator pos, It first, It last) {
+    iterator result = pos - cbegin() + begin();
+    while (first != last) {
+      insert(pos++, *first++);
+    }
+    return result;
+  }
+
+  iterator insert(const_iterator pos, T value) {
+    if (size_ == N) {
+      throw CapacityError();
+    }
+    int i = pos - cbegin();
+    size_ += 1;
+    std::move_backward(&data_[i], &data_[size_ - 1], &data_[size_]);
+    data_[i] = std::move(value);
+    return begin() + i;
+  }
+
+  template <class... Args>
+  iterator emplace(const_iterator pos, Args&&... args) {
+    return insert(pos, T(std::forward<Args>(args)...));
+  }
+
+  iterator erase(const_iterator first, const_iterator last) {
+    int i = first - cbegin();
+    int j = last - cbegin();
+    std::move(&data_[j], &data_[size_], &data_[i]);
+    size_ -= (last - first);
+    return begin() + i;
+  }
+
+  iterator erase(const_iterator pos) { return erase(pos, std::next(pos)); }
+
+private:
+  T data_[N];
+  std::size_t size_ = 0;
+};
+
+#endif // SUPPORT_NAIVE_STATIC_VECTOR_H

libcxx/test/std/containers/container.adaptors/flat.map.syn/sorted_unique.pass.cpp

@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// struct sorted_unique_t { explicit sorted_unique_t() = default; };
+// inline constexpr sorted_unique_t sorted_unique{};
+
+#include <cassert>
+#include <concepts>
+#include <flat_map>
+#include <type_traits>
+
+template <class T>
+void implicit_test(T) {}
+
+template <class T>
+concept HasImplicitDefaultCtor = requires { implicit_test<T>({}); };
+
+static_assert(std::is_default_constructible_v<std::sorted_unique_t>);
+static_assert(std::is_trivially_default_constructible_v<std::sorted_unique_t>);
+static_assert(!HasImplicitDefaultCtor<std::sorted_unique_t>);
+
+constexpr bool test() {
+  { [[maybe_unused]] std::sorted_unique_t s; }
+  { [[maybe_unused]] std::same_as<const std::sorted_unique_t&> decltype(auto) s = (std::sorted_unique); }
+  { [[maybe_unused]] std::same_as<const std::sorted_unique_t> decltype(auto) copy = std::sorted_unique; }
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/at.pass.cpp

@@ -0,0 +1,92 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+//       mapped_type& at(const key_type& k);
+// const mapped_type& at(const key_type& k) const;
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <stdexcept>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using P = std::pair<int, double>;
+  P ar[]  = {
+      P(1, 1.5),
+      P(2, 2.5),
+      P(3, 3.5),
+      P(4, 4.5),
+      P(5, 5.5),
+      P(7, 7.5),
+      P(8, 8.5),
+  };
+  const int one = 1;
+  {
+    std::flat_map<int, double, std::less<int>, KeyContainer, ValueContainer> m(ar, ar + sizeof(ar) / sizeof(ar[0]));
+    ASSERT_SAME_TYPE(decltype(m.at(one)), double&);
+    assert(m.size() == 7);
+    assert(m.at(one) == 1.5);
+    m.at(1) = -1.5;
+    assert(m.at(1) == -1.5);
+    assert(m.at(2) == 2.5);
+    assert(m.at(3) == 3.5);
+    assert(m.at(4) == 4.5);
+    assert(m.at(5) == 5.5);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try {
+      TEST_IGNORE_NODISCARD m.at(6);
+      assert(false);
+    } catch (std::out_of_range&) {
+    }
+#endif
+    assert(m.at(7) == 7.5);
+    assert(m.at(8) == 8.5);
+    assert(m.size() == 7);
+  }
+  {
+    const std::flat_map<int, double, std::less<int>, KeyContainer, ValueContainer> m(
+        ar, ar + sizeof(ar) / sizeof(ar[0]));
+    ASSERT_SAME_TYPE(decltype(m.at(one)), const double&);
+    assert(m.size() == 7);
+    assert(m.at(one) == 1.5);
+    assert(m.at(2) == 2.5);
+    assert(m.at(3) == 3.5);
+    assert(m.at(4) == 4.5);
+    assert(m.at(5) == 5.5);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try {
+      TEST_IGNORE_NODISCARD m.at(6);
+      assert(false);
+    } catch (std::out_of_range&) {
+    }
+#endif
+    assert(m.at(7) == 7.5);
+    assert(m.at(8) == 8.5);
+    assert(m.size() == 7);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/at_transparent.pass.cpp

@@ -0,0 +1,111 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class K> mapped_type&       at(const K& x);
+// template<class K> const mapped_type& at(const K& x) const;
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <stdexcept>
+
+#include "../helpers.h"
+#include "min_allocator.h"
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+
+// Constraints: The qualified-id Compare::is_transparent is valid and denotes a type.
+template <class M>
+concept CanAt           = requires(M m, Transparent<int> k) { m.at(k); };
+using TransparentMap    = std::flat_map<int, double, TransparentComparator>;
+using NonTransparentMap = std::flat_map<int, double, NonTransparentComparator>;
+static_assert(CanAt<TransparentMap>);
+static_assert(CanAt<const TransparentMap>);
+static_assert(!CanAt<NonTransparentMap>);
+static_assert(!CanAt<const NonTransparentMap>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using P = std::pair<int, double>;
+  P ar[]  = {
+      P(1, 1.5),
+      P(2, 2.5),
+      P(3, 3.5),
+      P(4, 4.5),
+      P(5, 5.5),
+      P(7, 7.5),
+      P(8, 8.5),
+  };
+  const Transparent<int> one{1};
+  {
+    std::flat_map<int, double, TransparentComparator, KeyContainer, ValueContainer> m(
+        ar, ar + sizeof(ar) / sizeof(ar[0]));
+    ASSERT_SAME_TYPE(decltype(m.at(one)), double&);
+    assert(m.size() == 7);
+    assert(m.at(one) == 1.5);
+    m.at(one) = -1.5;
+    assert(m.at(Transparent<int>{1}) == -1.5);
+    assert(m.at(Transparent<int>{2}) == 2.5);
+    assert(m.at(Transparent<int>{3}) == 3.5);
+    assert(m.at(Transparent<int>{4}) == 4.5);
+    assert(m.at(Transparent<int>{5}) == 5.5);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try {
+      TEST_IGNORE_NODISCARD m.at(Transparent<int>{6});
+      assert(false);
+    } catch (std::out_of_range&) {
+    }
+#endif
+    assert(m.at(Transparent<int>{7}) == 7.5);
+    assert(m.at(Transparent<int>{8}) == 8.5);
+    assert(m.size() == 7);
+  }
+  {
+    const std::flat_map<int, double, TransparentComparator, KeyContainer, ValueContainer> m(
+        ar, ar + sizeof(ar) / sizeof(ar[0]));
+    ASSERT_SAME_TYPE(decltype(m.at(one)), const double&);
+    assert(m.size() == 7);
+    assert(m.at(Transparent<int>{1}) == 1.5);
+    assert(m.at(Transparent<int>{2}) == 2.5);
+    assert(m.at(Transparent<int>{3}) == 3.5);
+    assert(m.at(Transparent<int>{4}) == 4.5);
+    assert(m.at(Transparent<int>{5}) == 5.5);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    try {
+      TEST_IGNORE_NODISCARD m.at(Transparent<int>{6});
+      assert(false);
+    } catch (std::out_of_range&) {
+    }
+#endif
+    assert(m.at(Transparent<int>{7}) == 7.5);
+    assert(m.at(Transparent<int>{8}) == 8.5);
+    assert(m.size() == 7);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    m.at(Transparent<int>{3});
+    assert(transparent_used);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/index_key.pass.cpp

@@ -0,0 +1,77 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// mapped_type& operator[](const key_type& k);
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+
+// Constraints: is_constructible_v<mapped_type> is true.
+template <class M, class Input>
+concept CanIndex = requires(M m, Input k) { m[k]; };
+
+static_assert(CanIndex<std::flat_map<int, double>, const int&>);
+static_assert(!CanIndex<std::flat_map<int, NoDefaultCtr>, const int&>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using P = std::pair<int, double>;
+  P ar[]  = {
+      P(1, 1.5),
+      P(2, 2.5),
+      P(3, 3.5),
+      P(4, 4.5),
+      P(5, 5.5),
+      P(7, 7.5),
+      P(8, 8.5),
+  };
+  const int one = 1;
+  std::flat_map<int, double, std::less<int>, KeyContainer, ValueContainer> m(ar, ar + sizeof(ar) / sizeof(ar[0]));
+  ASSERT_SAME_TYPE(decltype(m[one]), double&);
+  assert(m.size() == 7);
+  assert(m[one] == 1.5);
+  assert(m.size() == 7);
+  m[1] = -1.5;
+  assert(m[1] == -1.5);
+  assert(m.size() == 7);
+  assert(m[6] == 0);
+  assert(m.size() == 8);
+  m[6] = 6.5;
+  assert(m[6] == 6.5);
+  assert(m.size() == 8);
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto index_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap                             = std::decay_t<decltype(m)>;
+      const typename FlatMap::key_type key      = key_arg;
+      const typename FlatMap::mapped_type value = value_arg;
+      m[key]                                    = value;
+    };
+    test_emplace_exception_guarantee(index_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/index_rv_key.pass.cpp

@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// mapped_type& operator[](key_type&& k);
+
+#include <flat_map>
+#include <deque>
+#include <functional>
+#include <cassert>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "MoveOnly.h"
+#include "min_allocator.h"
+
+// Constraints: is_constructible_v<mapped_type> is true.
+template <class M, class Input>
+concept CanIndex = requires(M m, Input k) { m[k]; };
+
+static_assert(CanIndex<std::flat_map<int, double>, int&&>);
+static_assert(!CanIndex<std::flat_map<int, NoDefaultCtr>, int&&>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  {
+    std::flat_map<MoveOnly, double, std::less<MoveOnly>, KeyContainer, ValueContainer> m;
+    ASSERT_SAME_TYPE(decltype(m[MoveOnly{}]), double&);
+    assert(m.size() == 0);
+    assert(m[1] == 0.0);
+    assert(m.size() == 1);
+    m[1] = -1.5;
+    assert(m[1] == -1.5);
+    assert(m.size() == 1);
+    assert(m[6] == 0);
+    assert(m.size() == 2);
+    m[6] = 6.5;
+    assert(m[6] == 6.5);
+    assert(m.size() == 2);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<MoveOnly>, std::vector<double>>();
+  test<std::deque<MoveOnly>, std::vector<double>>();
+  test<MinSequenceContainer<MoveOnly>, MinSequenceContainer<double>>();
+  test<std::vector<MoveOnly, min_allocator<MoveOnly>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto index_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap                             = std::decay_t<decltype(m)>;
+      typename FlatMap::key_type key            = key_arg;
+      const typename FlatMap::mapped_type value = value_arg;
+      m[std::move(key)]                         = value;
+    };
+    test_emplace_exception_guarantee(index_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/index_transparent.pass.cpp

@@ -0,0 +1,107 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class K> mapped_type& operator[](K&& x);
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+// Constraints:
+// The qualified-id Compare::is_transparent is valid and denotes a type.
+// is_constructible_v<key_type, K> is true.
+// is_constructible_v<mapped_type, Args...> is true.
+// is_convertible_v<K&&, const_iterator> and is_convertible_v<K&&, iterator> are both false
+template <class M, class Input>
+concept CanIndex                      = requires(M m, Input k) { m[k]; };
+using TransparentMap                  = std::flat_map<int, double, TransparentComparator>;
+using NonTransparentMap               = std::flat_map<int, double, NonTransparentComparator>;
+using TransparentNoDefaultCtrValueMap = std::flat_map<int, NoDefaultCtr, TransparentComparator>;
+
+static_assert(CanIndex<TransparentMap, ConvertibleTransparent<int>>);
+static_assert(!CanIndex<const TransparentMap, ConvertibleTransparent<int>>);
+
+static_assert(!CanIndex<NonTransparentMap, NonConvertibleTransparent<int>>);
+static_assert(!CanIndex<const NonTransparentMap, NonConvertibleTransparent<int>>);
+
+static_assert(!CanIndex<TransparentMap, NonConvertibleTransparent<int>>);
+static_assert(!CanIndex<const TransparentMap, NonConvertibleTransparent<int>>);
+
+static_assert(!CanIndex<TransparentNoDefaultCtrValueMap, ConvertibleTransparent<int>>);
+static_assert(!CanIndex<const TransparentNoDefaultCtrValueMap, ConvertibleTransparent<int>>);
+
+static_assert(!CanIndex<TransparentMap, TransparentMap::iterator>);
+static_assert(!CanIndex<TransparentMap, TransparentMap::const_iterator>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using P = std::pair<int, double>;
+  P ar[]  = {
+      P(1, 1.5),
+      P(2, 2.5),
+      P(3, 3.5),
+      P(4, 4.5),
+      P(5, 5.5),
+      P(7, 7.5),
+      P(8, 8.5),
+  };
+  const ConvertibleTransparent<int> one{1};
+  const ConvertibleTransparent<int> six{6};
+  {
+    std::flat_map<int, double, TransparentComparator, KeyContainer, ValueContainer> m(
+        ar, ar + sizeof(ar) / sizeof(ar[0]));
+    ASSERT_SAME_TYPE(decltype(m[one]), double&);
+    assert(m.size() == 7);
+    assert(m[one] == 1.5);
+    assert(m.size() == 7);
+    m[one] = -1.5;
+    assert(m[one] == -1.5);
+    assert(m.size() == 7);
+    assert(m[six] == 0);
+    assert(m.size() == 8);
+    m[six] = 6.5;
+    assert(m[six] == 6.5);
+    assert(m.size() == 8);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    m[ConvertibleTransparent<int>{3}];
+    assert(transparent_used);
+  }
+  {
+    auto index_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap                             = std::decay_t<decltype(m)>;
+      using Key                                 = typename FlatMap::key_type;
+      const typename FlatMap::mapped_type value = value_arg;
+      m[ConvertibleTransparent<Key>{key_arg}]   = value;
+    };
+    test_emplace_exception_guarantee(index_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.capacity/empty.pass.cpp

@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// [[nodiscard]] bool empty() const noexcept;
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using M = std::flat_map<int, double, std::less<int>, KeyContainer, ValueContainer>;
+  M m;
+  ASSERT_SAME_TYPE(decltype(m.empty()), bool);
+  ASSERT_NOEXCEPT(m.empty());
+  assert(m.empty());
+  assert(std::as_const(m).empty());
+  m = {{1, 1.0}};
+  assert(!m.empty());
+  m.clear();
+  assert(m.empty());
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.capacity/empty.verify.cpp

@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// [[nodiscard]] bool empty() const noexcept;
+
+#include <flat_map>
+
+#include "test_macros.h"
+
+int main(int, char**) {
+  std::flat_map<int, int> c;
+  c.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.capacity/max_size.pass.cpp

@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// size_type max_size() const noexcept;
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <limits>
+#include <type_traits>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "test_allocator.h"
+#include "test_macros.h"
+
+int main(int, char**) {
+  {
+    using A1 = limited_allocator<int, 10>;
+    using A2 = limited_allocator<int, 20>;
+    using C  = std::flat_map<int, int, std::less<int>, std::vector<int, A1>, std::vector<int, A2>>;
+    ASSERT_SAME_TYPE(C::difference_type, std::ptrdiff_t);
+    ASSERT_SAME_TYPE(C::size_type, std::size_t);
+    const C c;
+    ASSERT_NOEXCEPT(c.max_size());
+    ASSERT_SAME_TYPE(decltype(c.max_size()), C::size_type);
+    assert(c.max_size() <= 10);
+    LIBCPP_ASSERT(c.max_size() == 10);
+  }
+  {
+    using A1 = limited_allocator<int, 10>;
+    using A2 = limited_allocator<int, 20>;
+    using C  = std::flat_map<int, int, std::less<int>, std::vector<int, A2>, std::vector<int, A1>>;
+    ASSERT_SAME_TYPE(C::difference_type, std::ptrdiff_t);
+    ASSERT_SAME_TYPE(C::size_type, std::size_t);
+    const C c;
+    ASSERT_NOEXCEPT(c.max_size());
+    ASSERT_SAME_TYPE(decltype(c.max_size()), C::size_type);
+    assert(c.max_size() <= 10);
+    LIBCPP_ASSERT(c.max_size() == 10);
+  }
+  {
+    using A = limited_allocator<int, (size_t)-1>;
+    using C = std::flat_map<int, int, std::less<int>, std::vector<int, A>, std::vector<int, A>>;
+    ASSERT_SAME_TYPE(C::difference_type, std::ptrdiff_t);
+    ASSERT_SAME_TYPE(C::size_type, std::size_t);
+    const C::size_type max_dist = static_cast<C::size_type>(std::numeric_limits<C::difference_type>::max());
+    const C c;
+    ASSERT_NOEXCEPT(c.max_size());
+    ASSERT_SAME_TYPE(decltype(c.max_size()), C::size_type);
+    assert(c.max_size() <= max_dist);
+    LIBCPP_ASSERT(c.max_size() == max_dist);
+  }
+  {
+    typedef std::flat_map<char, char> C;
+    ASSERT_SAME_TYPE(C::difference_type, std::ptrdiff_t);
+    ASSERT_SAME_TYPE(C::size_type, std::size_t);
+    const C::size_type max_dist = static_cast<C::size_type>(std::numeric_limits<C::difference_type>::max());
+    const C c;
+    ASSERT_NOEXCEPT(c.max_size());
+    ASSERT_SAME_TYPE(decltype(c.max_size()), C::size_type);
+    assert(c.max_size() <= max_dist);
+    assert(c.max_size() <= alloc_max_size(std::allocator<char>()));
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.capacity/size.pass.cpp

@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// size_type size() const noexcept;
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using M = std::flat_map<int, char, std::less<int>, KeyContainer, ValueContainer>;
+  {
+    const M m = {{1, 'a'}, {1, 'b'}, {4, 'd'}, {5, 'e'}, {5, 'h'}};
+    ASSERT_SAME_TYPE(decltype(m.size()), std::size_t);
+    ASSERT_NOEXCEPT(m.size());
+    assert(m.size() == 3);
+  }
+  {
+    const M m = {{1, 'a'}};
+    ASSERT_SAME_TYPE(decltype(m.size()), std::size_t);
+    ASSERT_NOEXCEPT(m.size());
+    assert(m.size() == 1);
+  }
+  {
+    const M m;
+    ASSERT_SAME_TYPE(decltype(m.size()), std::size_t);
+    ASSERT_NOEXCEPT(m.size());
+    assert(m.size() == 0);
+  }
+  {
+    M m;
+    std::size_t s = 1000000;
+    for (auto i = 0u; i < s; ++i) {
+      m.emplace(i, 'a');
+    }
+    ASSERT_SAME_TYPE(decltype(m.size()), std::size_t);
+    ASSERT_NOEXCEPT(m.size());
+    assert(m.size() == s);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<char>>();
+  test<std::deque<int>, std::vector<char>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<char>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<char, min_allocator<char>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/alloc.pass.cpp

@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class Allocator>
+//   explicit flat_map(const Allocator& a);
+
+#include <cassert>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "../../../test_compare.h"
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    static_assert(std::is_constructible_v<M1, const A1&>);
+    static_assert(!std::is_constructible_v<M1, const A2&>);
+    static_assert(!std::is_constructible_v<M2, const A2&>);
+    static_assert(!std::is_constructible_v<M3, const A2&>);
+  }
+  {
+    // explicit
+    using M =
+        std::flat_map<int,
+                      long,
+                      std::less<int>,
+                      std::vector<int, test_allocator<int>>,
+                      std::vector<long, test_allocator<long>>>;
+
+    static_assert(std::is_constructible_v<M, test_allocator<int>>);
+    static_assert(!std::is_convertible_v<test_allocator<int>, M>);
+  }
+  {
+    using A = test_allocator<short>;
+    using M =
+        std::flat_map<int,
+                      long,
+                      std::less<int>,
+                      std::vector<int, test_allocator<int>>,
+                      std::vector<long, test_allocator<long>>>;
+    M m(A(0, 5));
+    assert(m.empty());
+    assert(m.begin() == m.end());
+    assert(m.keys().get_allocator().get_id() == 5);
+    assert(m.values().get_allocator().get_id() == 5);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/assign_initializer_list.pass.cpp

@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map& operator=(initializer_list<value_type> il);
+
+#include <algorithm>
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <ranges>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+#include "test_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  {
+    M m = {{8, 8}, {10, 10}};
+    assert(m.size() == 2);
+    m                              = {{3, 0}, {1, 0}, {2, 0}, {2, 1}, {3, 1}, {4, 0}, {3, 2}, {5, 0}, {6, 0}, {5, 1}};
+    std::pair<int, int> expected[] = {{1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}};
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+  }
+  {
+    M m = {{10, 1}, {8, 1}};
+    assert(m.size() == 2);
+    m                                    = {{3, 2}};
+    std::pair<double, double> expected[] = {{3, 2}};
+    assert(std::ranges::equal(m, expected));
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<int>>();
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/compare.pass.cpp

@@ -0,0 +1,93 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// explicit flat_map(const key_compare& comp);
+// template <class Alloc>
+//   flat_map(const key_compare& comp, const Alloc& a);
+
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <type_traits>
+#include <vector>
+
+#include "test_macros.h"
+#include "../../../test_compare.h"
+#include "test_allocator.h"
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using M1 = std::flat_map<int, int, C, std::vector<int, A1>, std::vector<int, A1>>;
+    using M2 = std::flat_map<int, int, C, std::vector<int, A1>, std::vector<int, A2>>;
+    using M3 = std::flat_map<int, int, C, std::vector<int, A2>, std::vector<int, A1>>;
+    static_assert(std::is_constructible_v<M1, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, const C&, const A2&>);
+  }
+  {
+    using C = test_less<int>;
+    auto m  = std::flat_map<int, char*, C>(C(3));
+    assert(m.empty());
+    assert(m.begin() == m.end());
+    assert(m.key_comp() == C(3));
+  }
+  {
+    // The one-argument ctor is explicit.
+    using C = test_less<int>;
+    static_assert(std::is_constructible_v<std::flat_map<int, char*, C>, C>);
+    static_assert(!std::is_convertible_v<C, std::flat_map<int, char*, C>>);
+
+    static_assert(std::is_constructible_v<std::flat_map<int, char*>, std::less<int>>);
+    static_assert(!std::is_convertible_v<std::less<int>, std::flat_map<int, char*>>);
+  }
+  {
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    auto m   = std::flat_map<int, short, C, std::vector<int, A1>, std::vector<short, A2>>(C(4), A1(5));
+    assert(m.empty());
+    assert(m.begin() == m.end());
+    assert(m.key_comp() == C(4));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // explicit(false)
+    using C                                                                    = test_less<int>;
+    using A1                                                                   = test_allocator<int>;
+    using A2                                                                   = test_allocator<short>;
+    std::flat_map<int, short, C, std::deque<int, A1>, std::deque<short, A2>> m = {C(4), A1(5)};
+    assert(m.empty());
+    assert(m.begin() == m.end());
+    assert(m.key_comp() == C(4));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // If an allocator is given, it must be usable by both containers.
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, std::less<>, std::vector<int>, std::vector<int, A>>;
+    static_assert(std::is_constructible_v<M, std::less<>>);
+    static_assert(!std::is_constructible_v<M, std::less<>, std::allocator<int>>);
+    static_assert(!std::is_constructible_v<M, std::less<>, A>);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/containers.pass.cpp

@@ -0,0 +1,184 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(key_container_type key_cont, mapped_container_type mapped_cont,
+//           const key_compare& comp = key_compare());
+// template<class Allocator>
+//   flat_map(const key_container_type& key_cont, const mapped_container_type& mapped_cont,
+//            const Allocator& a);
+// template<class Alloc>
+//   flat_map(const key_container_type& key_cont, const mapped_container_type& mapped_cont,
+//            const key_compare& comp, const Alloc& a);
+
+#include <algorithm>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "min_allocator.h"
+#include "MoveOnly.h"
+#include "test_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+
+struct P {
+  int first;
+  int second;
+  template <class T, class U>
+  bool operator==(const std::pair<T, U>& rhs) const {
+    return MoveOnly(first) == rhs.first && MoveOnly(second) == rhs.second;
+  }
+};
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    static_assert(std::is_constructible_v<M1, const V1&, const V1&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, const V1&, const V1&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, const V1&, const V2&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, const V2&, const V1&, const A2&>);
+
+    static_assert(std::is_constructible_v<M1, const V1&, const V1&, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, const V1&, const V1&, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, const V1&, const V2&, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, const V2&, const V1&, const C&, const A2&>);
+  }
+  {
+    // flat_map(key_container_type , mapped_container_type)
+    using M              = std::flat_map<int, char>;
+    std::vector<int> ks  = {1, 1, 1, 2, 2, 3, 2, 3, 3};
+    std::vector<char> vs = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+    auto m               = M(ks, vs);
+    assert((m.keys() == std::vector<int>{1, 2, 3}));
+    LIBCPP_ASSERT((m.values() == std::vector<char>{1, 4, 6}));
+
+    // explicit(false)
+    M m2 = {ks, vs};
+    assert(m2 == m);
+
+    m = M(std::move(ks), std::move(vs));
+    assert(ks.empty()); // it was moved-from
+    assert(vs.empty()); // it was moved-from
+    assert((m.keys() == std::vector<int>{1, 2, 3}));
+    LIBCPP_ASSERT((m.values() == std::vector<char>{1, 4, 6}));
+  }
+  {
+    // flat_map(key_container_type , mapped_container_type)
+    // move-only
+    P expected[] = {{3, 2}, {2, 1}, {1, 3}};
+    using Ks     = std::deque<int, min_allocator<int>>;
+    using Vs     = std::vector<MoveOnly, min_allocator<MoveOnly>>;
+    using M      = std::flat_map<int, MoveOnly, std::greater<int>, Ks, Vs>;
+    Ks ks        = {1, 3, 2};
+    Vs vs;
+    vs.push_back(3);
+    vs.push_back(2);
+    vs.push_back(1);
+    auto m = M(std::move(ks), std::move(vs));
+    assert(ks.empty()); // it was moved-from
+    assert(vs.empty()); // it was moved-from
+    assert(std::ranges::equal(m, expected, std::equal_to<>()));
+  }
+  {
+    // flat_map(key_container_type , mapped_container_type)
+    // container's allocators are used
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, std::less<int>, std::vector<int, A>, std::deque<int, A>>;
+    auto ks = std::vector<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(5));
+    auto vs = std::deque<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(6));
+    auto m  = M(std::move(ks), std::move(vs));
+    assert(ks.empty()); // it was moved-from
+    assert(vs.empty()); // it was moved-from
+    assert((m == M{{1, 1}, {2, 2}, {3, 3}}));
+    assert(m.keys().get_allocator() == A(5));
+    assert(m.values().get_allocator() == A(6));
+  }
+  {
+    // flat_map(key_container_type , mapped_container_type, key_compare)
+    using C              = test_less<int>;
+    using M              = std::flat_map<int, char, C>;
+    std::vector<int> ks  = {1, 1, 1, 2, 2, 3, 2, 3, 3};
+    std::vector<char> vs = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+    auto m               = M(ks, vs, C(4));
+    assert((m.keys() == std::vector<int>{1, 2, 3}));
+    LIBCPP_ASSERT((m.values() == std::vector<char>{1, 4, 6}));
+    assert(m.key_comp() == C(4));
+
+    // explicit(false)
+    M m2 = {ks, vs, C(4)};
+    assert(m2 == m);
+    assert(m2.key_comp() == C(4));
+  }
+  {
+    // flat_map(key_container_type , mapped_container_type, const Allocator&)
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, std::less<int>, std::vector<int, A>, std::deque<int, A>>;
+    auto ks = std::vector<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(5));
+    auto vs = std::deque<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(6));
+    auto m  = M(ks, vs, A(4)); // replaces the allocators
+    assert(!ks.empty());       // it was an lvalue above
+    assert(!vs.empty());       // it was an lvalue above
+    assert((m == M{{1, 1}, {2, 2}, {3, 3}}));
+    assert(m.keys().get_allocator() == A(4));
+    assert(m.values().get_allocator() == A(4));
+  }
+  {
+    // flat_map(key_container_type , mapped_container_type, const Allocator&)
+    // explicit(false)
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, std::less<int>, std::vector<int, A>, std::deque<int, A>>;
+    auto ks = std::vector<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(5));
+    auto vs = std::deque<int, A>({1, 1, 1, 2, 2, 3, 2, 3, 3}, A(6));
+    M m     = {ks, vs, A(4)}; // implicit ctor
+    assert(!ks.empty());      // it was an lvalue above
+    assert(!vs.empty());      // it was an lvalue above
+    assert((m == M{{1, 1}, {2, 2}, {3, 3}}));
+    assert(m.keys().get_allocator() == A(4));
+    assert(m.values().get_allocator() == A(4));
+  }
+  {
+    // flat_map(key_container_type , mapped_container_type, key_compare, const Allocator&)
+    using C                = test_less<int>;
+    using A                = test_allocator<int>;
+    using M                = std::flat_map<int, int, C, std::vector<int, A>, std::vector<int, A>>;
+    std::vector<int, A> ks = {1, 1, 1, 2, 2, 3, 2, 3, 3};
+    std::vector<int, A> vs = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+    auto m                 = M(ks, vs, C(4), A(5));
+    assert((m.keys() == std::vector<int, A>{1, 2, 3}));
+    LIBCPP_ASSERT((m.values() == std::vector<int, A>{1, 4, 6}));
+    assert(m.key_comp() == C(4));
+    assert(m.keys().get_allocator() == A(5));
+    assert(m.values().get_allocator() == A(5));
+
+    // explicit(false)
+    M m2 = {ks, vs, C(4), A(5)};
+    assert(m2 == m);
+    assert(m2.key_comp() == C(4));
+    assert(m2.keys().get_allocator() == A(5));
+    assert(m2.values().get_allocator() == A(5));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/copy.pass.cpp

@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(const flat_map& m);
+
+#include <cassert>
+#include <flat_map>
+#include <vector>
+
+#include "test_macros.h"
+#include "../../../test_compare.h"
+#include "test_allocator.h"
+
+int main(int, char**) {
+  {
+    using C = test_less<int>;
+    std::vector<int, test_allocator<int>> ks({1, 3, 5}, test_allocator<int>(6));
+    std::vector<char, test_allocator<char>> vs({2, 2, 1}, test_allocator<char>(7));
+    using M = std::flat_map<int, char, C, decltype(ks), decltype(vs)>;
+    auto mo = M(ks, vs, C(5));
+    auto m  = mo;
+
+    assert(m.key_comp() == C(5));
+    assert(m.keys() == ks);
+    assert(m.values() == vs);
+    assert(m.keys().get_allocator() == test_allocator<int>(6));
+    assert(m.values().get_allocator() == test_allocator<char>(7));
+
+    // mo is unchanged
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys() == ks);
+    assert(mo.values() == vs);
+    assert(mo.keys().get_allocator() == test_allocator<int>(6));
+    assert(mo.values().get_allocator() == test_allocator<char>(7));
+  }
+  {
+    using C  = test_less<int>;
+    using Ks = std::vector<int, other_allocator<int>>;
+    using Vs = std::vector<char, other_allocator<char>>;
+    auto ks  = Ks({1, 3, 5}, other_allocator<int>(6));
+    auto vs  = Vs({2, 2, 1}, other_allocator<char>(7));
+    using M  = std::flat_map<int, char, C, Ks, Vs>;
+    auto mo  = M(Ks(ks, other_allocator<int>(6)), Vs(vs, other_allocator<int>(7)), C(5));
+    auto m   = mo;
+
+    assert(m.key_comp() == C(5));
+    assert(m.keys() == ks);
+    assert(m.values() == vs);
+    assert(m.keys().get_allocator() == other_allocator<int>(-2));
+    assert(m.values().get_allocator() == other_allocator<char>(-2));
+
+    // mo is unchanged
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys() == ks);
+    assert(mo.values() == vs);
+    assert(mo.keys().get_allocator() == other_allocator<int>(6));
+    assert(mo.values().get_allocator() == other_allocator<char>(7));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/copy_alloc.pass.cpp

@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(const flat_map&, const allocator_type&);
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "test_macros.h"
+#include "../../../test_compare.h"
+#include "test_allocator.h"
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    static_assert(std::is_constructible_v<M1, const M1&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, const M1&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, const M2&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, const M3&, const A2&>);
+  }
+  {
+    using C = test_less<int>;
+    std::vector<int, test_allocator<int>> ks({1, 3, 5}, test_allocator<int>(6));
+    std::vector<char, test_allocator<char>> vs({2, 2, 1}, test_allocator<char>(7));
+    using M = std::flat_map<int, char, C, decltype(ks), decltype(vs)>;
+    auto mo = M(ks, vs, C(5));
+    auto m  = M(mo, test_allocator<int>(3));
+
+    assert(m.key_comp() == C(5));
+    assert(m.keys() == ks);
+    assert(m.values() == vs);
+    assert(m.keys().get_allocator() == test_allocator<int>(3));
+    assert(m.values().get_allocator() == test_allocator<char>(3));
+
+    // mo is unchanged
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys() == ks);
+    assert(mo.values() == vs);
+    assert(mo.keys().get_allocator() == test_allocator<int>(6));
+    assert(mo.values().get_allocator() == test_allocator<char>(7));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/copy_assign.addressof.compile.pass.cpp

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map& operator=(const flat_map& s);
+
+// Validate whether the container can be copy-assigned (move-assigned, swapped)
+// with an ADL-hijacking operator&
+
+#include <flat_map>
+#include <utility>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::flat_map<operator_hijacker, operator_hijacker> so;
+  std::flat_map<operator_hijacker, operator_hijacker> s;
+  s = so;
+  s = std::move(so);
+  swap(s, so);
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/copy_assign.pass.cpp

@@ -0,0 +1,92 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map& operator=(const flat_map& m);
+
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "test_macros.h"
+#include "../../../test_compare.h"
+#include "test_allocator.h"
+
+int main(int, char**) {
+  {
+    // test_allocator is not propagated
+    using C = test_less<int>;
+    std::vector<int, test_allocator<int>> ks({1, 3, 5}, test_allocator<int>(6));
+    std::vector<char, test_allocator<char>> vs({2, 2, 1}, test_allocator<char>(7));
+    using M = std::flat_map<int, char, C, decltype(ks), decltype(vs)>;
+    auto mo = M(ks, vs, C(5));
+    auto m  = M({{3, 3}, {4, 4}, {5, 5}}, C(3), test_allocator<int>(2));
+    m       = mo;
+
+    assert(m.key_comp() == C(5));
+    assert(m.keys() == ks);
+    assert(m.values() == vs);
+    assert(m.keys().get_allocator() == test_allocator<int>(2));
+    assert(m.values().get_allocator() == test_allocator<char>(2));
+
+    // mo is unchanged
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys() == ks);
+    assert(mo.values() == vs);
+    assert(mo.keys().get_allocator() == test_allocator<int>(6));
+    assert(mo.values().get_allocator() == test_allocator<char>(7));
+  }
+  {
+    // other_allocator is propagated
+    using C  = test_less<int>;
+    using Ks = std::vector<int, other_allocator<int>>;
+    using Vs = std::vector<char, other_allocator<char>>;
+    auto ks  = Ks({1, 3, 5}, other_allocator<int>(6));
+    auto vs  = Vs({2, 2, 1}, other_allocator<char>(7));
+    using M  = std::flat_map<int, char, C, Ks, Vs>;
+    auto mo  = M(Ks(ks, other_allocator<int>(6)), Vs(vs, other_allocator<int>(7)), C(5));
+    auto m   = M({{3, 3}, {4, 4}, {5, 5}}, C(3), other_allocator<int>(2));
+    m        = mo;
+
+    assert(m.key_comp() == C(5));
+    assert(m.keys() == ks);
+    assert(m.values() == vs);
+    assert(m.keys().get_allocator() == other_allocator<int>(6));
+    assert(m.values().get_allocator() == other_allocator<char>(7));
+
+    // mo is unchanged
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys() == ks);
+    assert(mo.values() == vs);
+    assert(mo.keys().get_allocator() == other_allocator<int>(6));
+    assert(mo.values().get_allocator() == other_allocator<char>(7));
+  }
+  {
+    // comparator is copied and invariant is preserved
+    using M = std::flat_map<int, int, std::function<bool(int, int)>>;
+    M mo    = M({{1, 2}, {3, 4}}, std::less<int>());
+    M m     = M({{1, 2}, {3, 4}}, std::greater<int>());
+    assert(m.key_comp()(2, 1) == true);
+    assert(m != mo);
+    m = mo;
+    assert(m.key_comp()(2, 1) == false);
+    assert(m == mo);
+  }
+  {
+    // self-assignment
+    using M = std::flat_map<int, int>;
+    M m     = {{1, 2}, {3, 4}};
+    m       = static_cast<const M&>(m);
+    assert((m == M{{1, 2}, {3, 4}}));
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/deduct.pass.cpp

@@ -0,0 +1,342 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+#include <algorithm>
+#include <cassert>
+#include <climits>
+#include <deque>
+#include <initializer_list>
+#include <list>
+#include <flat_map>
+#include <functional>
+#include <ranges>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "deduction_guides_sfinae_checks.h"
+#include "test_allocator.h"
+
+using P  = std::pair<int, long>;
+using PC = std::pair<const int, long>;
+
+void test_copy() {
+  {
+    std::flat_map<long, short> source = {{1, 2}, {2, 3}};
+    std::flat_map s(source);
+    ASSERT_SAME_TYPE(decltype(s), decltype(source));
+    assert(s == source);
+  }
+  {
+    std::flat_map<long, short, std::greater<long>> source = {{1, 2}, {2, 3}};
+    std::flat_map s{source}; // braces instead of parens
+    ASSERT_SAME_TYPE(decltype(s), decltype(source));
+    assert(s == source);
+  }
+  {
+    std::flat_map<long, short, std::greater<long>> source = {{1, 2}, {2, 3}};
+    std::flat_map s(source, std::allocator<int>());
+    ASSERT_SAME_TYPE(decltype(s), decltype(source));
+    assert(s == source);
+  }
+}
+
+void test_containers() {
+  std::deque<int, test_allocator<int>> ks({1, 2, 1, INT_MAX, 3}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> vs({1, 2, 1, 4, 5}, test_allocator<int>(0, 43));
+  std::deque<int, test_allocator<int>> sorted_ks({1, 2, 3, INT_MAX}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> sorted_vs({1, 2, 5, 4}, test_allocator<int>(0, 43));
+  const std::pair<int, short> expected[] = {{1, 1}, {2, 2}, {3, 5}, {INT_MAX, 4}};
+  {
+    std::flat_map s(ks, vs);
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::less<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 42);
+    assert(s.values().get_allocator().get_id() == 43);
+  }
+  {
+    std::flat_map s(std::sorted_unique, sorted_ks, sorted_vs);
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::less<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 42);
+    assert(s.values().get_allocator().get_id() == 43);
+  }
+  {
+    std::flat_map s(ks, vs, test_allocator<long>(0, 44));
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::less<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 44);
+    assert(s.values().get_allocator().get_id() == 44);
+  }
+  {
+    std::flat_map s(std::sorted_unique, sorted_ks, sorted_vs, test_allocator<long>(0, 44));
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::less<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 44);
+    assert(s.values().get_allocator().get_id() == 44);
+  }
+}
+
+void test_containers_compare() {
+  std::deque<int, test_allocator<int>> ks({1, 2, 1, INT_MAX, 3}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> vs({1, 2, 1, 4, 5}, test_allocator<int>(0, 43));
+  std::deque<int, test_allocator<int>> sorted_ks({INT_MAX, 3, 2, 1}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> sorted_vs({4, 5, 2, 1}, test_allocator<int>(0, 43));
+  const std::pair<int, short> expected[] = {{INT_MAX, 4}, {3, 5}, {2, 2}, {1, 1}};
+  {
+    std::flat_map s(ks, vs, std::greater<int>());
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::greater<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 42);
+    assert(s.values().get_allocator().get_id() == 43);
+  }
+  {
+    std::flat_map s(std::sorted_unique, sorted_ks, sorted_vs, std::greater<int>());
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::greater<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 42);
+    assert(s.values().get_allocator().get_id() == 43);
+  }
+  {
+    std::flat_map s(ks, vs, std::greater<int>(), test_allocator<long>(0, 44));
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::greater<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 44);
+    assert(s.values().get_allocator().get_id() == 44);
+  }
+  {
+    std::flat_map s(std::sorted_unique, sorted_ks, sorted_vs, std::greater<int>(), test_allocator<long>(0, 44));
+
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::greater<int>, decltype(ks), decltype(vs)>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 44);
+    assert(s.values().get_allocator().get_id() == 44);
+  }
+}
+
+void test_iter_iter() {
+  const P arr[]          = {{1, 1L}, {2, 2L}, {1, 1L}, {INT_MAX, 1L}, {3, 1L}};
+  const P sorted_arr[]   = {{1, 1L}, {2, 2L}, {3, 1L}, {INT_MAX, 1L}};
+  const PC arrc[]        = {{1, 1L}, {2, 2L}, {1, 1L}, {INT_MAX, 1L}, {3, 1L}};
+  const PC sorted_arrc[] = {{1, 1L}, {2, 2L}, {3, 1L}, {INT_MAX, 1L}};
+  {
+    std::flat_map m(std::begin(arr), std::end(arr));
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::begin(arrc), std::end(arrc));
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::sorted_unique, std::begin(sorted_arr), std::end(sorted_arr));
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::sorted_unique, std::begin(sorted_arrc), std::end(sorted_arrc));
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map<int, short> mo;
+    std::flat_map m(mo.begin(), mo.end());
+    ASSERT_SAME_TYPE(decltype(m), decltype(mo));
+  }
+  {
+    std::flat_map<int, short> mo;
+    std::flat_map m(mo.cbegin(), mo.cend());
+    ASSERT_SAME_TYPE(decltype(m), decltype(mo));
+  }
+}
+
+void test_iter_iter_compare() {
+  const P arr[]          = {{1, 1L}, {2, 2L}, {1, 1L}, {INT_MAX, 1L}, {3, 1L}};
+  const P sorted_arr[]   = {{INT_MAX, 1L}, {3, 1L}, {2, 2L}, {1, 1L}};
+  const PC arrc[]        = {{1, 1L}, {2, 2L}, {1, 1L}, {INT_MAX, 1L}, {3, 1L}};
+  const PC sorted_arrc[] = {{INT_MAX, 1L}, {3, 1L}, {2, 2L}, {1, 1L}};
+  using C                = std::greater<long long>;
+  {
+    std::flat_map m(std::begin(arr), std::end(arr), C());
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long, C>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::begin(arrc), std::end(arrc), C());
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long, C>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::sorted_unique, std::begin(sorted_arr), std::end(sorted_arr), C());
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long, C>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::sorted_unique, std::begin(sorted_arrc), std::end(sorted_arrc), C());
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long, C>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map<int, short> mo;
+    std::flat_map m(mo.begin(), mo.end(), C());
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, short, C>);
+  }
+  {
+    std::flat_map<int, short> mo;
+    std::flat_map m(mo.cbegin(), mo.cend(), C());
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, short, C>);
+  }
+}
+
+void test_initializer_list() {
+  const P sorted_arr[] = {{1, 1L}, {2, 2L}, {3, 1L}, {INT_MAX, 1L}};
+  {
+    std::flat_map m{std::pair{1, 1L}, {2, 2L}, {1, 1L}, {INT_MAX, 1L}, {3, 1L}};
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::sorted_unique, {std::pair{1, 1L}, {2, 2L}, {3, 1L}, {INT_MAX, 1L}});
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+}
+
+void test_initializer_list_compare() {
+  const P sorted_arr[] = {{INT_MAX, 1L}, {3, 1L}, {2, 2L}, {1, 1L}};
+  using C              = std::greater<long long>;
+  {
+    std::flat_map m({std::pair{1, 1L}, {2, 2L}, {1, 1L}, {INT_MAX, 1L}, {3, 1L}}, C());
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long, C>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+  {
+    std::flat_map m(std::sorted_unique, {std::pair{INT_MAX, 1L}, {3, 1L}, {2, 2L}, {1, 1L}}, C());
+
+    ASSERT_SAME_TYPE(decltype(m), std::flat_map<int, long, C>);
+    assert(std::ranges::equal(m, sorted_arr));
+  }
+}
+
+void test_from_range() {
+  std::list<std::pair<int, short>> r     = {{1, 1}, {2, 2}, {1, 1}, {INT_MAX, 4}, {3, 5}};
+  const std::pair<int, short> expected[] = {{1, 1}, {2, 2}, {3, 5}, {INT_MAX, 4}};
+  {
+    std::flat_map s(std::from_range, r);
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::less<int>>);
+    assert(std::ranges::equal(s, expected));
+  }
+  {
+    std::flat_map s(std::from_range, r, test_allocator<long>(0, 42));
+    ASSERT_SAME_TYPE(
+        decltype(s),
+        std::flat_map<int,
+                      short,
+                      std::less<int>,
+                      std::vector<int, test_allocator<int>>,
+                      std::vector<short, test_allocator<short>>>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 42);
+    assert(s.values().get_allocator().get_id() == 42);
+  }
+}
+
+void test_from_range_compare() {
+  std::list<std::pair<int, short>> r     = {{1, 1}, {2, 2}, {1, 1}, {INT_MAX, 4}, {3, 5}};
+  const std::pair<int, short> expected[] = {{INT_MAX, 4}, {3, 5}, {2, 2}, {1, 1}};
+  {
+    std::flat_map s(std::from_range, r, std::greater<int>());
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, short, std::greater<int>>);
+    assert(std::ranges::equal(s, expected));
+  }
+  {
+    std::flat_map s(std::from_range, r, std::greater<int>(), test_allocator<long>(0, 42));
+    ASSERT_SAME_TYPE(
+        decltype(s),
+        std::flat_map<int,
+                      short,
+                      std::greater<int>,
+                      std::vector<int, test_allocator<int>>,
+                      std::vector<short, test_allocator<short>>>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().get_id() == 42);
+    assert(s.values().get_allocator().get_id() == 42);
+  }
+}
+
+int main(int, char**) {
+  // Each test function also tests the sorted_unique-prefixed and allocator-suffixed overloads.
+  test_copy();
+  test_containers();
+  test_containers_compare();
+  test_iter_iter();
+  test_iter_iter_compare();
+  test_initializer_list();
+  test_initializer_list_compare();
+  test_from_range();
+  test_from_range_compare();
+
+  AssociativeContainerDeductionGuidesSfinaeAway<std::flat_map, std::flat_map<int, short>>();
+  {
+    std::flat_map s = {std::make_pair(1, 'a')}; // flat_map(initializer_list<pair<int, char>>)
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, char>);
+    assert(s.size() == 1);
+  }
+  {
+    using M = std::flat_map<int, short>;
+    M m;
+    std::flat_map s = {std::make_pair(m, m)}; // flat_map(initializer_list<pair<M, M>>)
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<M, M>);
+    assert(s.size() == 1);
+    assert(s[m] == m);
+  }
+
+  {
+    std::pair<int, int> source[3] = {{1, 1}, {2, 2}, {3, 3}};
+    std::flat_map s               = {source, source + 3}; // flat_map(InputIterator, InputIterator)
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, int>);
+    assert(s.size() == 3);
+  }
+  {
+    std::pair<int, int> source[3] = {{1, 1}, {2, 2}, {3, 3}};
+    std::flat_map s{source, source + 3}; // flat_map(InputIterator, InputIterator)
+    ASSERT_SAME_TYPE(decltype(s), std::flat_map<int, int>);
+    assert(s.size() == 3);
+  }
+  {
+    std::pair<int, int> source[3] = {{1, 1}, {2, 2}, {3, 3}};
+    std::flat_map s{std::sorted_unique, source, source + 3}; // flat_map(sorted_unique_t, InputIterator, InputIterator)
+    static_assert(std::is_same_v<decltype(s), std::flat_map<int, int>>);
+    assert(s.size() == 3);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/deduct.verify.cpp

@@ -0,0 +1,97 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// Test CTAD on cases where deduction should fail.
+
+#include <flat_map>
+#include <functional>
+#include <memory>
+#include <utility>
+#include <vector>
+
+struct NotAnAllocator {
+  friend bool operator<(NotAnAllocator, NotAnAllocator) { return false; }
+};
+
+using P  = std::pair<int, long>;
+using PC = std::pair<const int, long>;
+
+void test() {
+  {
+    // cannot deduce Key and T from just (KeyContainer), even if it's a container of pairs
+    std::vector<std::pair<int, int>> v;
+    std::flat_map s(v);
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce Key and T from just (KeyContainer, Allocator)
+    std::vector<int> v;
+    std::flat_map s(v, std::allocator<std::pair<const int, int>>());
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce Key and T from nothing
+    std::flat_map m;
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce Key and T from just (Compare)
+    std::flat_map m(std::less<int>{});
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce Key and T from just (Compare, Allocator)
+    std::flat_map m(std::less<int>{}, std::allocator<PC>{});
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce Key and T from just (Allocator)
+    std::flat_map m(std::allocator<PC>{});
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot convert from some arbitrary unrelated type
+    NotAnAllocator a;
+    std::flat_map m(a);
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce that the inner braced things should be std::pair and not something else
+    std::flat_map m{{1, 1L}, {2, 2L}, {3, 3L}};
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce that the inner braced things should be std::pair and not something else
+    std::flat_map m({{1, 1L}, {2, 2L}, {3, 3L}}, std::less<int>());
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce that the inner braced things should be std::pair and not something else
+    std::flat_map m({{1, 1L}, {2, 2L}, {3, 3L}}, std::less<int>(), std::allocator<PC>());
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // cannot deduce that the inner braced things should be std::pair and not something else
+    std::flat_map m({{1, 1L}, {2, 2L}, {3, 3L}}, std::allocator<PC>());
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // since we have parens, not braces, this deliberately does not find the initializer_list constructor
+    std::flat_map m(P{1, 1L});
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+  {
+    // since we have parens, not braces, this deliberately does not find the initializer_list constructor
+    std::flat_map m(PC{1, 1L});
+    // expected-error-re@-1{{{{no viable constructor or deduction guide for deduction of template arguments of '.*flat_map'}}}}
+  }
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/deduct_pmr.pass.cpp

@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: availability-pmr-missing
+
+// <flat_map>
+
+#include <algorithm>
+#include <cassert>
+#include <climits>
+#include <deque>
+#include <initializer_list>
+#include <list>
+#include <flat_map>
+#include <functional>
+#include <memory_resource>
+#include <ranges>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "test_allocator.h"
+
+using P  = std::pair<int, long>;
+using PC = std::pair<const int, long>;
+
+void test_containers() {
+  std::deque<int, test_allocator<int>> ks({1, 2, 1, INT_MAX, 3}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> vs({1, 2, 1, 4, 5}, test_allocator<int>(0, 43));
+  std::deque<int, test_allocator<int>> sorted_ks({1, 2, 3, INT_MAX}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> sorted_vs({1, 2, 5, 4}, test_allocator<int>(0, 43));
+  const std::pair<int, short> expected[] = {{1, 1}, {2, 2}, {3, 5}, {INT_MAX, 4}};
+  {
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::monotonic_buffer_resource mr2;
+    std::pmr::deque<int> pks(ks.begin(), ks.end(), &mr);
+    std::pmr::deque<short> pvs(vs.begin(), vs.end(), &mr);
+    std::flat_map s(std::move(pks), std::move(pvs), &mr2);
+
+    ASSERT_SAME_TYPE(
+        decltype(s), std::flat_map<int, short, std::less<int>, std::pmr::deque<int>, std::pmr::deque<short>>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().resource() == &mr2);
+    assert(s.values().get_allocator().resource() == &mr2);
+  }
+  {
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::monotonic_buffer_resource mr2;
+    std::pmr::deque<int> pks(sorted_ks.begin(), sorted_ks.end(), &mr);
+    std::pmr::deque<short> pvs(sorted_vs.begin(), sorted_vs.end(), &mr);
+    std::flat_map s(std::sorted_unique, std::move(pks), std::move(pvs), &mr2);
+
+    ASSERT_SAME_TYPE(
+        decltype(s), std::flat_map<int, short, std::less<int>, std::pmr::deque<int>, std::pmr::deque<short>>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().resource() == &mr2);
+    assert(s.values().get_allocator().resource() == &mr2);
+  }
+}
+
+void test_containers_compare() {
+  std::deque<int, test_allocator<int>> ks({1, 2, 1, INT_MAX, 3}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> vs({1, 2, 1, 4, 5}, test_allocator<int>(0, 43));
+  std::deque<int, test_allocator<int>> sorted_ks({INT_MAX, 3, 2, 1}, test_allocator<int>(0, 42));
+  std::deque<short, test_allocator<short>> sorted_vs({4, 5, 2, 1}, test_allocator<int>(0, 43));
+  const std::pair<int, short> expected[] = {{INT_MAX, 4}, {3, 5}, {2, 2}, {1, 1}};
+  {
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::monotonic_buffer_resource mr2;
+    std::pmr::deque<int> pks(ks.begin(), ks.end(), &mr);
+    std::pmr::deque<short> pvs(vs.begin(), vs.end(), &mr);
+    std::flat_map s(std::move(pks), std::move(pvs), std::greater<int>(), &mr2);
+
+    ASSERT_SAME_TYPE(
+        decltype(s), std::flat_map<int, short, std::greater<int>, std::pmr::deque<int>, std::pmr::deque<short>>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().resource() == &mr2);
+    assert(s.values().get_allocator().resource() == &mr2);
+  }
+  {
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::monotonic_buffer_resource mr2;
+    std::pmr::deque<int> pks(sorted_ks.begin(), sorted_ks.end(), &mr);
+    std::pmr::deque<short> pvs(sorted_vs.begin(), sorted_vs.end(), &mr);
+    std::flat_map s(std::sorted_unique, std::move(pks), std::move(pvs), std::greater<int>(), &mr2);
+
+    ASSERT_SAME_TYPE(
+        decltype(s), std::flat_map<int, short, std::greater<int>, std::pmr::deque<int>, std::pmr::deque<short>>);
+    assert(std::ranges::equal(s, expected));
+    assert(s.keys().get_allocator().resource() == &mr2);
+    assert(s.values().get_allocator().resource() == &mr2);
+  }
+}
+
+int main(int, char**) {
+  test_containers();
+  test_containers_compare();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/default.pass.cpp

@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map();
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <type_traits>
+#include <vector>
+
+#include "test_macros.h"
+#include "min_allocator.h"
+#include "test_allocator.h"
+
+struct DefaultCtableComp {
+  explicit DefaultCtableComp() { default_constructed_ = true; }
+  bool operator()(int, int) const { return false; }
+  bool default_constructed_ = false;
+};
+
+int main(int, char**) {
+  {
+    std::flat_map<int, char*> m;
+    assert(m.empty());
+  }
+  {
+    // explicit(false)
+    std::flat_map<int, char*> m = {};
+    assert(m.empty());
+  }
+  {
+    std::flat_map<int, char*, DefaultCtableComp, std::deque<int, min_allocator<int>>> m;
+    assert(m.empty());
+    assert(m.begin() == m.end());
+    assert(m.key_comp().default_constructed_);
+  }
+  {
+    using A1 = explicit_allocator<int>;
+    using A2 = explicit_allocator<char*>;
+    {
+      std::flat_map<int, char*, DefaultCtableComp, std::vector<int, A1>, std::vector<char*, A2>> m;
+      assert(m.empty());
+      assert(m.key_comp().default_constructed_);
+    }
+    {
+      A1 a1;
+      std::flat_map<int, int, DefaultCtableComp, std::vector<int, A1>, std::vector<int, A1>> m(a1);
+      assert(m.empty());
+      assert(m.key_comp().default_constructed_);
+    }
+  }
+  {
+    // If an allocator is given, it must be usable by both containers.
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, std::less<>, std::vector<int>, std::vector<int, A>>;
+    static_assert(std::is_constructible_v<M>);
+    static_assert(!std::is_constructible_v<M, std::allocator<int>>);
+    static_assert(!std::is_constructible_v<M, A>);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/default_noexcept.pass.cpp

@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map()
+//    noexcept(
+//        is_nothrow_default_constructible_v<key_container_type> &&
+//        is_nothrow_default_constructible_v<mapped_container_type> &&
+//        is_nothrow_default_constructible_v<key_compare>);
+
+// This tests a conforming extension
+
+#include <cassert>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "test_macros.h"
+#include "MoveOnly.h"
+#include "test_allocator.h"
+
+struct ThrowingCtorComp {
+  ThrowingCtorComp() noexcept(false) {}
+  bool operator()(const auto&, const auto&) const { return false; }
+};
+
+int main(int, char**) {
+#if defined(_LIBCPP_VERSION)
+  {
+    using C = std::flat_map<MoveOnly, MoveOnly>;
+    static_assert(std::is_nothrow_default_constructible_v<C>);
+  }
+  {
+    using C = std::flat_map<MoveOnly, MoveOnly, std::less<MoveOnly>, std::vector<MoveOnly, test_allocator<MoveOnly>>>;
+    static_assert(std::is_nothrow_default_constructible_v<C>);
+  }
+#endif // _LIBCPP_VERSION
+  {
+    using C = std::flat_map<MoveOnly, MoveOnly, std::less<MoveOnly>, std::vector<MoveOnly, other_allocator<MoveOnly>>>;
+    static_assert(!std::is_nothrow_default_constructible_v<C>);
+    C c;
+  }
+  {
+    using C = std::flat_map<MoveOnly, MoveOnly, ThrowingCtorComp>;
+    static_assert(!std::is_nothrow_default_constructible_v<C>);
+    C c;
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/dtor_noexcept.pass.cpp

@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// ~flat_map();
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "test_macros.h"
+#include "MoveOnly.h"
+#include "test_allocator.h"
+
+struct ThrowingDtorComp {
+  bool operator()(const auto&, const auto&) const;
+  ~ThrowingDtorComp() noexcept(false);
+};
+
+int main(int, char**) {
+  {
+    using C = std::flat_map<MoveOnly, MoveOnly>;
+    static_assert(std::is_nothrow_destructible_v<C>);
+  }
+  {
+    using V = std::vector<MoveOnly, test_allocator<MoveOnly>>;
+    using C = std::flat_map<MoveOnly, MoveOnly, std::less<MoveOnly>, V, V>;
+    static_assert(std::is_nothrow_destructible_v<C>);
+  }
+  {
+    using V = std::deque<MoveOnly, other_allocator<MoveOnly>>;
+    using C = std::flat_map<MoveOnly, MoveOnly, std::greater<MoveOnly>, V, V>;
+    static_assert(std::is_nothrow_destructible_v<C>);
+  }
+#if defined(_LIBCPP_VERSION)
+  {
+    using C = std::flat_map<MoveOnly, MoveOnly, ThrowingDtorComp>;
+    static_assert(!std::is_nothrow_destructible_v<C>);
+  }
+#endif // _LIBCPP_VERSION
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/initializer_list.pass.cpp

@@ -0,0 +1,157 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(initializer_list<value_type> il, const key_compare& comp = key_compare());
+// template<class Alloc>
+//    flat_map(initializer_list<value_type> il, const Alloc& a);
+// template<class Alloc>
+//    flat_map(initializer_list<value_type> il, const key_compare& comp, const Alloc& a);
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <type_traits>
+#include <vector>
+
+#include "test_macros.h"
+#include "min_allocator.h"
+#include "test_allocator.h"
+
+#include "../../../test_compare.h"
+
+struct DefaultCtableComp {
+  explicit DefaultCtableComp() { default_constructed_ = true; }
+  bool operator()(int, int) const { return false; }
+  bool default_constructed_ = false;
+};
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    using IL = std::initializer_list<std::pair<int, int>>;
+    static_assert(std::is_constructible_v<M1, IL, const A1&>);
+    static_assert(!std::is_constructible_v<M1, IL, const A2&>);
+    static_assert(!std::is_constructible_v<M2, IL, const A2&>);
+    static_assert(!std::is_constructible_v<M3, IL, const A2&>);
+
+    static_assert(std::is_constructible_v<M1, IL, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, IL, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, IL, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, IL, const C&, const A2&>);
+  }
+
+  {
+    // initializer_list<value_type> needs to match exactly
+    using M = std::flat_map<int, short>;
+    using C = typename M::key_compare;
+    static_assert(std::is_constructible_v<M, std::initializer_list<std::pair<int, short>>>);
+    static_assert(std::is_constructible_v<M, std::initializer_list<std::pair<int, short>>, C>);
+    static_assert(std::is_constructible_v<M, std::initializer_list<std::pair<int, short>>, C, std::allocator<int>>);
+    static_assert(std::is_constructible_v<M, std::initializer_list<std::pair<int, short>>, std::allocator<int>>);
+    static_assert(!std::is_constructible_v<M, std::initializer_list<std::pair<const int, short>>>);
+    static_assert(!std::is_constructible_v<M, std::initializer_list<std::pair<const int, short>>, C>);
+    static_assert(
+        !std::is_constructible_v<M, std::initializer_list<std::pair<const int, short>>, C, std::allocator<int>>);
+    static_assert(!std::is_constructible_v<M, std::initializer_list<std::pair<const int, short>>, std::allocator<int>>);
+    static_assert(!std::is_constructible_v<M, std::initializer_list<std::pair<const int, const short>>>);
+    static_assert(!std::is_constructible_v<M, std::initializer_list<std::pair<const int, const short>>, C>);
+    static_assert(
+        !std::is_constructible_v<M, std::initializer_list<std::pair<const int, const short>>, C, std::allocator<int>>);
+    static_assert(
+        !std::is_constructible_v<M, std::initializer_list<std::pair<const int, const short>>, std::allocator<int>>);
+  }
+
+  std::pair<int, short> expected[] = {{1, 1}, {2, 2}, {3, 3}, {5, 2}};
+  {
+    // flat_map(initializer_list<value_type>);
+    using M                                         = std::flat_map<int, short>;
+    std::initializer_list<std::pair<int, short>> il = {{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}};
+    M m(il);
+    assert(std::equal(m.begin(), m.end(), expected, expected + 4));
+  }
+  {
+    // flat_map(initializer_list<value_type>);
+    // explicit(false)
+    using M = std::flat_map<int, short>;
+    M m     = {{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}};
+    assert(std::equal(m.begin(), m.end(), expected, expected + 4));
+  }
+  {
+    // flat_map(initializer_list<value_type>);
+    using M = std::flat_map<int, short, std::greater<int>, std::deque<int, min_allocator<int>>>;
+    M m     = {{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}};
+    assert(std::equal(m.rbegin(), m.rend(), expected, expected + 4));
+  }
+  {
+    using A = explicit_allocator<int>;
+    {
+      // flat_map(initializer_list<value_type>);
+      // different comparator
+      using M = std::flat_map<int, int, DefaultCtableComp, std::vector<int, A>, std::deque<int, A>>;
+      M m     = {{1, 1}, {2, 2}, {3, 3}};
+      assert(m.size() == 1);
+      assert(m.begin()->first == m.begin()->second);
+      LIBCPP_ASSERT(*m.begin() == std::make_pair(1, 1));
+      assert(m.key_comp().default_constructed_);
+    }
+    {
+      // flat_map(initializer_list<value_type>, const Allocator&);
+      using M = std::flat_map<int, int, std::greater<int>, std::deque<int, A>, std::vector<int, A>>;
+      A a;
+      M m({{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}}, a);
+      assert(std::equal(m.rbegin(), m.rend(), expected, expected + 4));
+    }
+  }
+  {
+    // flat_map(initializer_list<value_type>, const key_compare&);
+    using C = test_less<int>;
+    using M = std::flat_map<int, short, C>;
+    auto m  = M({{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}}, C(10));
+    assert(std::equal(m.begin(), m.end(), expected, expected + 4));
+    assert(m.key_comp() == C(10));
+
+    // explicit(false)
+    M m2 = {{{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}}, C(10)};
+    assert(m2 == m);
+    assert(m2.key_comp() == C(10));
+  }
+  {
+    // flat_map(initializer_list<value_type>, const key_compare&);
+    // Sorting uses the comparator that was passed in
+    using M = std::flat_map<int, short, std::function<bool(int, int)>, std::deque<int, min_allocator<int>>>;
+    auto m  = M({{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}}, std::greater<int>());
+    assert(std::equal(m.rbegin(), m.rend(), expected, expected + 4));
+    assert(m.key_comp()(2, 1) == true);
+  }
+  {
+    // flat_map(initializer_list<value_type> il, const key_compare& comp, const Alloc& a);
+    using A = explicit_allocator<int>;
+    using M = std::flat_map<int, int, std::greater<int>, std::deque<int, A>, std::vector<int, A>>;
+    A a;
+    M m({{5, 2}, {2, 2}, {2, 2}, {3, 3}, {1, 1}, {3, 3}}, {}, a);
+    assert(std::equal(m.rbegin(), m.rend(), expected, expected + 4));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/iter_iter.pass.cpp

@@ -0,0 +1,154 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template <class InputIterator>
+//   flat_map(InputIterator first, InputIterator last, const key_compare& comp = key_compare());
+// template<class InputIterator, class Allocator>
+//   flat_map(InputIterator first, InputIterator last, const Allocator& a);
+// template<class InputIterator, class Allocator>
+//   flat_map(InputIterator first, InputIterator last, const key_compare& comp, const Allocator& a);
+
+#include <algorithm>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "min_allocator.h"
+#include "test_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C     = test_less<int>;
+    using A1    = test_allocator<int>;
+    using A2    = other_allocator<int>;
+    using V1    = std::vector<int, A1>;
+    using V2    = std::vector<int, A2>;
+    using M1    = std::flat_map<int, int, C, V1, V1>;
+    using M2    = std::flat_map<int, int, C, V1, V2>;
+    using M3    = std::flat_map<int, int, C, V2, V1>;
+    using Iter1 = typename M1::iterator;
+    using Iter2 = typename M2::iterator;
+    using Iter3 = typename M3::iterator;
+    static_assert(std::is_constructible_v<M1, Iter1, Iter1, const A1&>);
+    static_assert(!std::is_constructible_v<M1, Iter1, Iter1, const A2&>);
+    static_assert(!std::is_constructible_v<M2, Iter2, Iter2, const A2&>);
+    static_assert(!std::is_constructible_v<M3, Iter3, Iter3, const A2&>);
+
+    static_assert(std::is_constructible_v<M1, Iter1, Iter1, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, Iter1, Iter1, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, Iter2, Iter2, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, Iter3, Iter3, const C&, const A2&>);
+  }
+
+  using P      = std::pair<int, short>;
+  P ar[]       = {{1, 1}, {1, 2}, {1, 3}, {2, 4}, {2, 5}, {3, 6}, {2, 7}, {3, 8}, {3, 9}};
+  P expected[] = {{1, 1}, {2, 4}, {3, 6}};
+  {
+    // flat_map(InputIterator , InputIterator)
+    // cpp17_input_iterator
+    using M = std::flat_map<int, short>;
+    auto m  = M(cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 9));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+
+    // explicit(false)
+    M m2 = {cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 9)};
+    assert(m2 == m);
+  }
+  {
+    // flat_map(InputIterator , InputIterator)
+    // greater
+    using M = std::flat_map<int, short, std::greater<int>, std::deque<int, min_allocator<int>>, std::deque<short>>;
+    auto m  = M(cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 9));
+    assert((m.keys() == std::deque<int, min_allocator<int>>{3, 2, 1}));
+    LIBCPP_ASSERT((m.values() == std::deque<short>{6, 4, 1}));
+  }
+  {
+    // flat_map(InputIterator , InputIterator)
+    // Test when the operands are of array type (also contiguous iterator type)
+    using M = std::flat_map<int, short, std::greater<int>, std::vector<int, min_allocator<int>>>;
+    auto m  = M(ar, ar);
+    assert(m.empty());
+  }
+  {
+    // flat_map(InputIterator , InputIterator, const key_compare&)
+    using C = test_less<int>;
+    using M = std::flat_map<int, short, C, std::vector<int>, std::deque<short>>;
+    auto m  = M(ar, ar + 9, C(3));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.key_comp() == C(3));
+
+    // explicit(false)
+    M m2 = {ar, ar + 9, C(3)};
+    assert(m2 == m);
+    assert(m2.key_comp() == C(3));
+  }
+  {
+    // flat_map(InputIterator , InputIterator, const Allocator&)
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, std::less<int>, std::vector<int, A1>, std::deque<short, A2>>;
+    auto m   = M(ar, ar + 9, A1(5));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(InputIterator , InputIterator, const Allocator&)
+    // explicit(false)
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, std::less<int>, std::vector<int, A1>, std::deque<short, A2>>;
+    M m      = {ar, ar + 9, A1(5)}; // implicit ctor
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(InputIterator , InputIterator, const key_compare&, const Allocator&)
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, C, std::vector<int, A1>, std::deque<short, A2>>;
+    auto m   = M(ar, ar + 9, C(3), A1(5));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.key_comp() == C(3));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(InputIterator , InputIterator, const key_compare&, const Allocator&)
+    // explicit(false)
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, std::less<int>, std::deque<int, A1>, std::vector<short, A2>>;
+    M m      = {ar, ar + 9, {}, A2(5)}; // implicit ctor
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/iter_iter_stability.pass.cpp

@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class InputIterator>
+//   flat_map(InputIterator first, InputIterator last, const key_compare& comp = key_compare())
+//
+// libc++ uses stable_sort to ensure that flat_map's behavior matches map's,
+// in terms of which duplicate items are kept.
+// This tests a conforming extension.
+
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <flat_map>
+#include <random>
+#include <map>
+
+#include "test_macros.h"
+
+struct Mod256 {
+  bool operator()(int x, int y) const { return (x % 256) < (y % 256); }
+};
+
+int main(int, char**) {
+  std::mt19937 randomness;
+  std::pair<uint16_t, uint16_t> pairs[200];
+  for (auto& pair : pairs) {
+    pair = {uint16_t(randomness()), uint16_t(randomness())};
+  }
+
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs, pairs + 200);
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(pairs, pairs + 200);
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs, pairs + 200, std::allocator<int>());
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(pairs, pairs + 200, std::allocator<int>());
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs, pairs + 200, Mod256());
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(pairs, pairs + 200, Mod256());
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  {
+    std::map<uint16_t, uint16_t, Mod256> m(pairs, pairs + 200, Mod256(), std::allocator<int>());
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(pairs, pairs + 200, Mod256(), std::allocator<int>());
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/move.pass.cpp

@@ -0,0 +1,88 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(flat_map&&);
+
+#include <algorithm>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "../helpers.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+int main(int, char**) {
+  {
+    using C = test_less<int>;
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, C, std::vector<int, A>, std::deque<int, A>>;
+    M mo    = M({{1, 1}, {2, 2}, {3, 1}}, C(5), A(7));
+    M m     = std::move(mo);
+    assert((m == M{{1, 1}, {2, 2}, {3, 1}}));
+    assert(m.key_comp() == C(5));
+    assert(m.keys().get_allocator() == A(7));
+    assert(m.values().get_allocator() == A(7));
+
+    assert(mo.empty());
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys().get_allocator().get_id() == test_alloc_base::moved_value);
+    assert(mo.values().get_allocator().get_id() == test_alloc_base::moved_value);
+  }
+  {
+    using C = test_less<int>;
+    using A = min_allocator<int>;
+    using M = std::flat_map<int, int, C, std::vector<int, A>, std::deque<int, A>>;
+    M mo    = M({{1, 1}, {2, 2}, {3, 1}}, C(5), A());
+    M m     = std::move(mo);
+    assert((m == M{{1, 1}, {2, 2}, {3, 1}}));
+    assert(m.key_comp() == C(5));
+    assert(m.keys().get_allocator() == A());
+    assert(m.values().get_allocator() == A());
+
+    assert(mo.empty());
+    assert(mo.key_comp() == C(5));
+    assert(m.keys().get_allocator() == A());
+    assert(m.values().get_allocator() == A());
+  }
+  {
+    // A moved-from flat_map maintains its class invariant in the presence of moved-from comparators.
+    using M = std::flat_map<int, int, std::function<bool(int, int)>>;
+    M mo    = M({{1, 1}, {2, 2}, {3, 1}}, std::less<int>());
+    M m     = std::move(mo);
+    assert(m.size() == 3);
+    assert(std::is_sorted(m.begin(), m.end(), m.value_comp()));
+    assert(m.key_comp()(1, 2) == true);
+
+    assert(std::is_sorted(mo.begin(), mo.end(), mo.value_comp()));
+    LIBCPP_ASSERT(m.key_comp()(1, 2) == true);
+    LIBCPP_ASSERT(mo.empty());
+    mo.insert({{1, 1}, {2, 2}, {3, 1}}); // insert has no preconditions
+    assert(m == mo);
+  }
+  {
+    // moved-from object maintains invariant if one of underlying container does not clear after move
+    using M = std::flat_map<int, int, std::less<>, std::vector<int>, CopyOnlyVector<int>>;
+    M m1    = M({1, 2, 3}, {1, 2, 3});
+    M m2    = std::move(m1);
+    assert(m2.size() == 3);
+    check_invariant(m1);
+    LIBCPP_ASSERT(m1.empty());
+    LIBCPP_ASSERT(m1.keys().size() == 0);
+    LIBCPP_ASSERT(m1.values().size() == 0);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/move_alloc.pass.cpp

@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(flat_map&&, const allocator_type&);
+
+#include <algorithm>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <ranges>
+#include <vector>
+
+#include "../helpers.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+#include "test_allocator.h"
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    static_assert(std::is_constructible_v<M1, M1&&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, M1&&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, M2&&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, M3&&, const A2&>);
+  }
+  {
+    std::pair<int, int> expected[] = {{1, 1}, {2, 2}, {3, 1}};
+    using C                        = test_less<int>;
+    using A                        = test_allocator<int>;
+    using M                        = std::flat_map<int, int, C, std::vector<int, A>, std::deque<int, A>>;
+    auto mo                        = M(expected, expected + 3, C(5), A(7));
+    auto m                         = M(std::move(mo), A(3));
+
+    assert(m.key_comp() == C(5));
+    assert(m.size() == 3);
+    auto [keys, values] = std::move(m).extract();
+    assert(keys.get_allocator() == A(3));
+    assert(values.get_allocator() == A(3));
+    assert(std::ranges::equal(keys, expected | std::views::elements<0>));
+    assert(std::ranges::equal(values, expected | std::views::elements<1>));
+
+    // The original flat_map is moved-from.
+    assert(std::is_sorted(mo.begin(), mo.end(), mo.value_comp()));
+    assert(mo.empty());
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys().get_allocator() == A(7));
+    assert(mo.values().get_allocator() == A(7));
+  }
+  {
+    // moved-from object maintains invariant if one of underlying container does not clear after move
+    using M = std::flat_map<int, int, std::less<>, std::vector<int>, CopyOnlyVector<int>>;
+    M m1    = M({1, 2, 3}, {1, 2, 3});
+    M m2(std::move(m1), std::allocator<int>{});
+    assert(m2.size() == 3);
+    check_invariant(m1);
+    LIBCPP_ASSERT(m1.empty());
+    LIBCPP_ASSERT(m1.keys().size() == 0);
+    LIBCPP_ASSERT(m1.values().size() == 0);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/move_assign.pass.cpp

@@ -0,0 +1,74 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map& operator=(flat_map&&);
+
+#include <algorithm>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "test_macros.h"
+#include "MoveOnly.h"
+#include "../../../test_compare.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+int main(int, char**) {
+  {
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<char>;
+    using M  = std::flat_map<int, char, C, std::vector<int, A1>, std::vector<char, A2>>;
+    M mo     = M({{1, 1}, {2, 3}, {3, 2}}, C(5), A1(7));
+    M m      = M({}, C(3), A1(7));
+    m        = std::move(mo);
+    assert((m == M{{1, 1}, {2, 3}, {3, 2}}));
+    assert(m.key_comp() == C(5));
+    auto [ks, vs] = std::move(m).extract();
+    assert(ks.get_allocator() == A1(7));
+    assert(vs.get_allocator() == A2(7));
+    assert(mo.empty());
+  }
+  {
+    using C  = test_less<int>;
+    using A1 = other_allocator<int>;
+    using A2 = other_allocator<char>;
+    using M  = std::flat_map<int, char, C, std::deque<int, A1>, std::deque<char, A2>>;
+    M mo     = M({{4, 5}, {5, 4}}, C(5), A1(7));
+    M m      = M({{1, 1}, {2, 2}, {3, 3}, {4, 4}}, C(3), A1(7));
+    m        = std::move(mo);
+    assert((m == M{{4, 5}, {5, 4}}));
+    assert(m.key_comp() == C(5));
+    auto [ks, vs] = std::move(m).extract();
+    assert(ks.get_allocator() == A1(7));
+    assert(vs.get_allocator() == A2(7));
+    assert(mo.empty());
+  }
+  {
+    using A = min_allocator<int>;
+    using M = std::flat_map<int, int, std::greater<int>, std::vector<int, A>, std::vector<int, A>>;
+    M mo    = M({{5, 1}, {4, 2}, {3, 3}}, A());
+    M m     = M({{4, 4}, {3, 3}, {2, 2}, {1, 1}}, A());
+    m       = std::move(mo);
+    assert((m == M{{5, 1}, {4, 2}, {3, 3}}));
+    auto [ks, vs] = std::move(m).extract();
+    assert(ks.get_allocator() == A());
+    assert(vs.get_allocator() == A());
+    assert(mo.empty());
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/move_assign_clears.pass.cpp

@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map& operator=(flat_map&&);
+// Preserves the class invariant for the moved-from flat_map.
+
+#include <algorithm>
+#include <cassert>
+#include <compare>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "../helpers.h"
+#include "test_macros.h"
+
+struct MoveNegates {
+  int value_    = 0;
+  MoveNegates() = default;
+  MoveNegates(int v) : value_(v) {}
+  MoveNegates(MoveNegates&& rhs) : value_(rhs.value_) { rhs.value_ = -rhs.value_; }
+  MoveNegates& operator=(MoveNegates&& rhs) {
+    value_     = rhs.value_;
+    rhs.value_ = -rhs.value_;
+    return *this;
+  }
+  ~MoveNegates()                             = default;
+  auto operator<=>(const MoveNegates&) const = default;
+};
+
+struct MoveClears {
+  int value_   = 0;
+  MoveClears() = default;
+  MoveClears(int v) : value_(v) {}
+  MoveClears(MoveClears&& rhs) : value_(rhs.value_) { rhs.value_ = 0; }
+  MoveClears& operator=(MoveClears&& rhs) {
+    value_     = rhs.value_;
+    rhs.value_ = 0;
+    return *this;
+  }
+  ~MoveClears()                             = default;
+  auto operator<=>(const MoveClears&) const = default;
+};
+
+int main(int, char**) {
+  auto value_eq = [](auto&& p, auto&& q) { return p.first == q.first; };
+  {
+    const std::pair<int, int> expected[] = {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}, {8, 8}};
+    using M = std::flat_map<MoveNegates, int, std::less<MoveNegates>, std::vector<MoveNegates>>;
+    M m     = M(expected, expected + 8);
+    M m2    = M(expected, expected + 3);
+
+    m2 = std::move(m);
+
+    assert(std::equal(m2.begin(), m2.end(), expected, expected + 8));
+    LIBCPP_ASSERT(m.empty());
+    assert(std::is_sorted(m.begin(), m.end(), m.value_comp()));          // still sorted
+    assert(std::adjacent_find(m.begin(), m.end(), value_eq) == m.end()); // still contains no duplicates
+    m.insert({1, 1});
+    m.insert({2, 2});
+    assert(m.contains(1));
+    assert(m.find(2) != m.end());
+  }
+  {
+    const std::pair<int, int> expected[] = {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}, {8, 8}};
+    using M = std::flat_map<MoveClears, int, std::less<MoveClears>, std::vector<MoveClears>>;
+    M m     = M(expected, expected + 8);
+    M m2    = M(expected, expected + 3);
+
+    m2 = std::move(m);
+
+    assert(std::equal(m2.begin(), m2.end(), expected, expected + 8));
+    LIBCPP_ASSERT(m.empty());
+    assert(std::is_sorted(m.begin(), m.end(), m.value_comp()));          // still sorted
+    assert(std::adjacent_find(m.begin(), m.end(), value_eq) == m.end()); // still contains no duplicates
+    m.insert({1, 1});
+    m.insert({2, 2});
+    assert(m.contains(1));
+    assert(m.find(2) != m.end());
+  }
+  {
+    // moved-from object maintains invariant if one of underlying container does not clear after move
+    using M = std::flat_map<int, int, std::less<>, std::vector<int>, CopyOnlyVector<int>>;
+    M m1    = M({1, 2, 3}, {1, 2, 3});
+    M m2    = M({1, 2}, {1, 2});
+    m2      = std::move(m1);
+    assert(m2.size() == 3);
+    check_invariant(m1);
+    LIBCPP_ASSERT(m1.empty());
+    LIBCPP_ASSERT(m1.keys().size() == 0);
+    LIBCPP_ASSERT(m1.values().size() == 0);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/move_assign_noexcept.pass.cpp

@@ -0,0 +1,110 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map& operator=(flat_map&& c)
+//     noexcept(
+//          is_nothrow_move_assignable<key_container_type>::value &&
+//          is_nothrow_move_assignable<mapped_container_type>::value &&
+//          is_nothrow_copy_assignable<key_compare>::value);
+
+// This tests a conforming extension
+
+#include <flat_map>
+#include <functional>
+#include <memory_resource>
+#include <type_traits>
+#include <vector>
+
+#include "MoveOnly.h"
+#include "test_allocator.h"
+#include "test_macros.h"
+
+struct MoveSensitiveComp {
+  MoveSensitiveComp() noexcept(false)                         = default;
+  MoveSensitiveComp(const MoveSensitiveComp&) noexcept(false) = default;
+  MoveSensitiveComp(MoveSensitiveComp&& rhs) { rhs.is_moved_from_ = true; }
+  MoveSensitiveComp& operator=(const MoveSensitiveComp&) noexcept = default;
+  MoveSensitiveComp& operator=(MoveSensitiveComp&& rhs) {
+    rhs.is_moved_from_ = true;
+    return *this;
+  }
+  bool operator()(const auto&, const auto&) const { return false; }
+  bool is_moved_from_ = false;
+};
+
+struct MoveThrowsComp {
+  MoveThrowsComp(MoveThrowsComp&&) noexcept(false);
+  MoveThrowsComp(const MoveThrowsComp&) noexcept(true);
+  MoveThrowsComp& operator=(MoveThrowsComp&&) noexcept(false);
+  MoveThrowsComp& operator=(const MoveThrowsComp&) noexcept(true);
+  bool operator()(const auto&, const auto&) const;
+};
+
+int main(int, char**) {
+  {
+    using C = std::flat_map<int, int>;
+    LIBCPP_STATIC_ASSERT(std::is_nothrow_move_assignable_v<C>);
+  }
+  {
+    using C =
+        std::flat_map<MoveOnly,
+                      int,
+                      std::less<MoveOnly>,
+                      std::vector<MoveOnly, test_allocator<MoveOnly>>,
+                      std::vector<int, test_allocator<int>>>;
+    static_assert(!std::is_nothrow_move_assignable_v<C>);
+  }
+  {
+    using C =
+        std::flat_map<int,
+                      MoveOnly,
+                      std::less<int>,
+                      std::vector<int, test_allocator<int>>,
+                      std::vector<MoveOnly, test_allocator<MoveOnly>>>;
+    static_assert(!std::is_nothrow_move_assignable_v<C>);
+  }
+  {
+    using C =
+        std::flat_map<MoveOnly,
+                      int,
+                      std::less<MoveOnly>,
+                      std::vector<MoveOnly, other_allocator<MoveOnly>>,
+                      std::vector<int, other_allocator<int>>>;
+    LIBCPP_STATIC_ASSERT(std::is_nothrow_move_assignable_v<C>);
+  }
+  {
+    using C =
+        std::flat_map<int,
+                      MoveOnly,
+                      std::less<int>,
+                      std::vector<int, other_allocator<int>>,
+                      std::vector<MoveOnly, other_allocator<MoveOnly>>>;
+    LIBCPP_STATIC_ASSERT(std::is_nothrow_move_assignable_v<C>);
+  }
+  {
+    // Test with a comparator that throws on move-assignment.
+    using C = std::flat_map<int, int, MoveThrowsComp>;
+    LIBCPP_STATIC_ASSERT(!std::is_nothrow_move_assignable_v<C>);
+  }
+  {
+    // Test with a container that throws on move-assignment.
+    using C = std::flat_map<int, int, std::less<int>, std::pmr::vector<int>, std::vector<int>>;
+    static_assert(!std::is_nothrow_move_assignable_v<C>);
+  }
+  {
+    // Test with a container that throws on move-assignment.
+    using C = std::flat_map<int, int, std::less<int>, std::vector<int>, std::pmr::vector<int>>;
+    static_assert(!std::is_nothrow_move_assignable_v<C>);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/move_exceptions.pass.cpp

@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: no-exceptions
+
+// <flat_map>
+
+// flat_map(flat_map&& s);
+// If any member function in [flat.map.defn] exits via an exception, the invariant is restored.
+
+#include <algorithm>
+#include <cassert>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "../helpers.h"
+#include "test_macros.h"
+
+static int countdown = 0;
+
+struct EvilContainer : std::vector<int> {
+  EvilContainer() = default;
+  EvilContainer(EvilContainer&& rhs) {
+    // Throw on move-construction.
+    if (--countdown == 0) {
+      rhs.insert(rhs.end(), 0);
+      rhs.insert(rhs.end(), 0);
+      throw 42;
+    }
+  }
+};
+
+int main(int, char**) {
+  {
+    using M   = std::flat_map<int, int, std::less<int>, EvilContainer, std::vector<int>>;
+    M mo      = {{1, 1}, {2, 2}, {3, 3}};
+    countdown = 1;
+    try {
+      M m = std::move(mo);
+      assert(false); // not reached
+    } catch (int x) {
+      assert(x == 42);
+    }
+    // The source flat_map maintains its class invariant.
+    check_invariant(mo);
+    LIBCPP_ASSERT(mo.empty());
+  }
+  {
+    using M   = std::flat_map<int, int, std::less<int>, std::vector<int>, EvilContainer>;
+    M mo      = {{1, 1}, {2, 2}, {3, 3}};
+    countdown = 1;
+    try {
+      M m = std::move(mo);
+      assert(false); // not reached
+    } catch (int x) {
+      assert(x == 42);
+    }
+    // The source flat_map maintains its class invariant.
+    check_invariant(mo);
+    LIBCPP_ASSERT(mo.empty());
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/move_noexcept.pass.cpp

@@ -0,0 +1,102 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(flat_map&&)
+//        noexcept(is_nothrow_move_constructible<key_container_type>::value &&
+//                 is_nothrow_move_constructible<mapped_container_type>::value &&
+//                 is_nothrow_copy_constructible<key_compare>::value);
+
+// This tests a conforming extension
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <memory>
+#include <type_traits>
+#include <vector>
+
+#include "test_macros.h"
+#include "MoveOnly.h"
+#include "test_allocator.h"
+
+template <class T>
+struct ThrowingMoveAllocator {
+  using value_type                                    = T;
+  explicit ThrowingMoveAllocator()                    = default;
+  ThrowingMoveAllocator(const ThrowingMoveAllocator&) = default;
+  ThrowingMoveAllocator(ThrowingMoveAllocator&&) noexcept(false) {}
+  T* allocate(std::ptrdiff_t n) { return std::allocator<T>().allocate(n); }
+  void deallocate(T* p, std::ptrdiff_t n) { return std::allocator<T>().deallocate(p, n); }
+  friend bool operator==(ThrowingMoveAllocator, ThrowingMoveAllocator) = default;
+};
+
+struct ThrowingMoveComp {
+  ThrowingMoveComp() = default;
+  ThrowingMoveComp(const ThrowingMoveComp&) noexcept(true) {}
+  ThrowingMoveComp(ThrowingMoveComp&&) noexcept(false) {}
+  bool operator()(const auto&, const auto&) const { return false; }
+};
+
+struct MoveSensitiveComp {
+  MoveSensitiveComp() noexcept(false)                  = default;
+  MoveSensitiveComp(const MoveSensitiveComp&) noexcept = default;
+  MoveSensitiveComp(MoveSensitiveComp&& rhs) { rhs.is_moved_from_ = true; }
+  MoveSensitiveComp& operator=(const MoveSensitiveComp&) noexcept(false) = default;
+  MoveSensitiveComp& operator=(MoveSensitiveComp&& rhs) {
+    rhs.is_moved_from_ = true;
+    return *this;
+  }
+  bool operator()(const auto&, const auto&) const { return false; }
+  bool is_moved_from_ = false;
+};
+
+int main(int, char**) {
+  {
+    using C = std::flat_map<int, int>;
+    LIBCPP_STATIC_ASSERT(std::is_nothrow_move_constructible_v<C>);
+    C c;
+    C d = std::move(c);
+  }
+  {
+    using C = std::flat_map<int, int, std::less<int>, std::deque<int, test_allocator<int>>>;
+    LIBCPP_STATIC_ASSERT(std::is_nothrow_move_constructible_v<C>);
+    C c;
+    C d = std::move(c);
+  }
+#if _LIBCPP_VERSION
+  {
+    // Container fails to be nothrow-move-constructible; this relies on libc++'s support for non-nothrow-copyable allocators
+    using C = std::flat_map<int, int, std::less<int>, std::deque<int, ThrowingMoveAllocator<int>>, std::vector<int>>;
+    static_assert(!std::is_nothrow_move_constructible_v<std::deque<int, ThrowingMoveAllocator<int>>>);
+    static_assert(!std::is_nothrow_move_constructible_v<C>);
+    C c;
+    C d = std::move(c);
+  }
+  {
+    // Container fails to be nothrow-move-constructible; this relies on libc++'s support for non-nothrow-copyable allocators
+    using C = std::flat_map<int, int, std::less<int>, std::vector<int>, std::deque<int, ThrowingMoveAllocator<int>>>;
+    static_assert(!std::is_nothrow_move_constructible_v<std::deque<int, ThrowingMoveAllocator<int>>>);
+    static_assert(!std::is_nothrow_move_constructible_v<C>);
+    C c;
+    C d = std::move(c);
+  }
+#endif // _LIBCPP_VERSION
+  {
+    // Comparator fails to be nothrow-move-constructible
+    using C = std::flat_map<int, int, ThrowingMoveComp>;
+    static_assert(!std::is_nothrow_move_constructible_v<C>);
+    C c;
+    C d = std::move(c);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/pmr.pass.cpp

@@ -0,0 +1,361 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: availability-pmr-missing
+
+// <flat_map>
+
+// Test various constructors with pmr
+
+#include <algorithm>
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <memory_resource>
+#include <ranges>
+#include <vector>
+#include <string>
+
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "../../../test_compare.h"
+
+int main(int, char**) {
+  {
+    // flat_map(const Allocator& a);
+    using M = std::flat_map<int, short, std::less<int>, std::pmr::vector<int>, std::pmr::vector<short>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::polymorphic_allocator<int> pa = &mr;
+    auto m1                                 = M(pa);
+    assert(m1.empty());
+    assert(m1.keys().get_allocator() == pa);
+    assert(m1.values().get_allocator() == pa);
+    auto m2 = M(&mr);
+    assert(m2.empty());
+    assert(m2.keys().get_allocator() == pa);
+    assert(m2.values().get_allocator() == pa);
+  }
+  {
+    // flat_map(const key_compare& comp, const Alloc& a);
+    using M = std::flat_map<int, int, std::function<bool(int, int)>, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    vm.emplace_back(std::greater<int>());
+    assert(vm[0] == M{});
+    assert(vm[0].key_comp()(2, 1) == true);
+    assert(vm[0].value_comp()({2, 0}, {1, 0}) == true);
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    // flat_map(const key_container_type& key_cont, const mapped_container_type& mapped_cont,
+    //          const Allocator& a);
+    using M = std::flat_map<int, int, std::less<int>, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    std::pmr::vector<int> ks = {1, 1, 1, 2, 2, 3, 2, 3, 3};
+    std::pmr::vector<int> vs = {1, 1, 1, 2, 2, 3, 2, 3, 3};
+    assert(ks.get_allocator().resource() != &mr);
+    assert(vs.get_allocator().resource() != &mr);
+    vm.emplace_back(ks, vs);
+    assert(ks.size() == 9); // ks' value is unchanged, since it was an lvalue above
+    assert(vs.size() == 9); // vs' value is unchanged, since it was an lvalue above
+    assert((vm[0] == M{{1, 1}, {2, 2}, {3, 3}}));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    // flat_map(const flat_map&, const allocator_type&);
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr1;
+    std::pmr::monotonic_buffer_resource mr2;
+    M mo = M({1, 2, 3}, {2, 2, 1}, C(5), &mr1);
+    M m  = {mo, &mr2}; // also test the implicitness of this constructor
+
+    assert(m.key_comp() == C(5));
+    assert((m.keys() == std::pmr::vector<int>{1, 2, 3}));
+    assert((m.values() == std::pmr::vector<int>{2, 2, 1}));
+    assert(m.keys().get_allocator().resource() == &mr2);
+    assert(m.values().get_allocator().resource() == &mr2);
+
+    // mo is unchanged
+    assert(mo.key_comp() == C(5));
+    assert((mo.keys() == std::pmr::vector<int>{1, 2, 3}));
+    assert((mo.values() == std::pmr::vector<int>{2, 2, 1}));
+    assert(mo.keys().get_allocator().resource() == &mr1);
+    assert(mo.values().get_allocator().resource() == &mr1);
+  }
+  {
+    // flat_map(const flat_map&, const allocator_type&);
+    using M = std::flat_map<int, int, std::less<>, std::pmr::vector<int>, std::pmr::deque<int>>;
+    std::pmr::vector<M> vs;
+    M m = {{1, 2}, {2, 2}, {3, 1}};
+    vs.push_back(m);
+    assert(vs[0] == m);
+  }
+  {
+    // flat_map& operator=(const flat_map& m);
+    // pmr allocator is not propagated
+    using M = std::flat_map<int, int, std::less<>, std::pmr::deque<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr1;
+    std::pmr::monotonic_buffer_resource mr2;
+    M mo = M({{1, 1}, {2, 2}, {3, 3}}, &mr1);
+    M m  = M({{4, 4}, {5, 5}}, &mr2);
+    m    = mo;
+    assert((m == M{{1, 1}, {2, 2}, {3, 3}}));
+    assert(m.keys().get_allocator().resource() == &mr2);
+    assert(m.values().get_allocator().resource() == &mr2);
+
+    // mo is unchanged
+    assert((mo == M{{1, 1}, {2, 2}, {3, 3}}));
+    assert(mo.keys().get_allocator().resource() == &mr1);
+  }
+  {
+    // flat_map(const flat_map& m);
+    using C = test_less<int>;
+    std::pmr::monotonic_buffer_resource mr;
+    using M = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::vector<int>>;
+    auto mo = M({{1, 1}, {2, 2}, {3, 3}}, C(5), &mr);
+    auto m  = mo;
+
+    assert(m.key_comp() == C(5));
+    assert((m == M{{1, 1}, {2, 2}, {3, 3}}));
+    auto [ks, vs] = std::move(m).extract();
+    assert(ks.get_allocator().resource() == std::pmr::get_default_resource());
+    assert(vs.get_allocator().resource() == std::pmr::get_default_resource());
+
+    // mo is unchanged
+    assert(mo.key_comp() == C(5));
+    assert((mo == M{{1, 1}, {2, 2}, {3, 3}}));
+    auto [kso, vso] = std::move(mo).extract();
+    assert(kso.get_allocator().resource() == &mr);
+    assert(vso.get_allocator().resource() == &mr);
+  }
+  {
+    //  flat_map(initializer_list<value_type> il, const Alloc& a);
+    using M = std::flat_map<int, int, std::less<int>, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    std::initializer_list<M::value_type> il = {{3, 3}, {1, 1}, {4, 4}, {1, 1}, {5, 5}};
+    vm.emplace_back(il);
+    assert((vm[0] == M{{1, 1}, {3, 3}, {4, 4}, {5, 5}}));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    //  flat_map(initializer_list<value_type> il, const key_compare& comp, const Alloc& a);
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::deque<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    std::initializer_list<M::value_type> il = {{3, 3}, {1, 1}, {4, 4}, {1, 1}, {5, 5}};
+    vm.emplace_back(il, C(5));
+    assert((vm[0] == M{{1, 1}, {3, 3}, {4, 4}, {5, 5}}));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+    assert(vm[0].key_comp() == C(5));
+  }
+  {
+    // flat_map(InputIterator first, InputIterator last, const Allocator& a);
+    using P      = std::pair<int, short>;
+    P ar[]       = {{1, 1}, {1, 2}, {1, 3}, {2, 4}, {2, 5}, {3, 6}, {2, 7}, {3, 8}, {3, 9}};
+    P expected[] = {{1, 1}, {2, 4}, {3, 6}};
+    {
+      //  cpp17 iterator
+      using M = std::flat_map<int, short, std::less<int>, std::pmr::vector<int>, std::pmr::vector<short>>;
+      std::pmr::monotonic_buffer_resource mr;
+      std::pmr::vector<M> vm(&mr);
+      vm.emplace_back(cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 9));
+      assert(std::ranges::equal(vm[0].keys(), expected | std::views::elements<0>));
+      LIBCPP_ASSERT(std::ranges::equal(vm[0], expected));
+      assert(vm[0].keys().get_allocator().resource() == &mr);
+      assert(vm[0].values().get_allocator().resource() == &mr);
+    }
+    {
+      using M = std::flat_map<int, short, std::less<int>, std::pmr::vector<int>, std::pmr::vector<short>>;
+      std::pmr::monotonic_buffer_resource mr;
+      std::pmr::vector<M> vm(&mr);
+      vm.emplace_back(ar, ar);
+      assert(vm[0].empty());
+      assert(vm[0].keys().get_allocator().resource() == &mr);
+      assert(vm[0].values().get_allocator().resource() == &mr);
+    }
+  }
+  {
+    // flat_map(flat_map&&, const allocator_type&);
+    std::pair<int, int> expected[] = {{1, 1}, {2, 2}, {3, 1}};
+    using C                        = test_less<int>;
+    using M                        = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::deque<int>>;
+    std::pmr::monotonic_buffer_resource mr1;
+    std::pmr::monotonic_buffer_resource mr2;
+    M mo = M({{1, 1}, {3, 1}, {1, 1}, {2, 2}}, C(5), &mr1);
+    M m  = {std::move(mo), &mr2}; // also test the implicitness of this constructor
+
+    assert(m.key_comp() == C(5));
+    assert(m.size() == 3);
+    assert(m.keys().get_allocator().resource() == &mr2);
+    assert(m.values().get_allocator().resource() == &mr2);
+    assert(std::equal(m.begin(), m.end(), expected, expected + 3));
+
+    // The original flat_map is moved-from.
+    assert(std::is_sorted(mo.begin(), mo.end(), mo.value_comp()));
+    assert(mo.key_comp() == C(5));
+    assert(mo.keys().get_allocator().resource() == &mr1);
+    assert(mo.values().get_allocator().resource() == &mr1);
+  }
+  {
+    // flat_map(flat_map&&, const allocator_type&);
+    using M = std::flat_map<int, int, std::less<>, std::pmr::deque<int>, std::pmr::vector<int>>;
+    std::pmr::vector<M> vs;
+    M m = {{1, 1}, {3, 1}, {1, 1}, {2, 2}};
+    vs.push_back(std::move(m));
+    assert((vs[0].keys() == std::pmr::deque<int>{1, 2, 3}));
+    assert((vs[0].values() == std::pmr::vector<int>{1, 2, 1}));
+  }
+  {
+    // flat_map& operator=(flat_map&&);
+    using M =
+        std::flat_map<std::pmr::string, int, std::less<>, std::pmr::vector<std::pmr::string>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr1;
+    std::pmr::monotonic_buffer_resource mr2;
+    M mo = M({{"short", 1},
+              {"very long string that definitely won't fit in the SSO buffer and therefore becomes empty on move", 2}},
+             &mr1);
+    M m  = M({{"don't care", 3}}, &mr2);
+    m    = std::move(mo);
+    assert(m.size() == 2);
+    assert(std::is_sorted(m.begin(), m.end(), m.value_comp()));
+    assert(m.begin()->first.get_allocator().resource() == &mr2);
+
+    assert(std::is_sorted(mo.begin(), mo.end(), mo.value_comp()));
+    mo.insert({"foo", 1});
+    assert(mo.begin()->first.get_allocator().resource() == &mr1);
+  }
+  {
+    //  flat_map(from_range_t, R&&, const Alloc&);
+    using P      = std::pair<int, short>;
+    P ar[]       = {{1, 1}, {1, 2}, {1, 3}, {2, 4}, {2, 5}, {3, 6}, {2, 7}, {3, 8}, {3, 9}};
+    P expected[] = {{1, 1}, {2, 4}, {3, 6}};
+    {
+      // input_range
+      using M    = std::flat_map<int, short, std::less<int>, std::pmr::vector<int>, std::pmr::vector<short>>;
+      using Iter = cpp20_input_iterator<const P*>;
+      using Sent = sentinel_wrapper<Iter>;
+      using R    = std::ranges::subrange<Iter, Sent>;
+      std::pmr::monotonic_buffer_resource mr;
+      std::pmr::vector<M> vm(&mr);
+      vm.emplace_back(std::from_range, R(Iter(ar), Sent(Iter(ar + 9))));
+      assert(std::ranges::equal(vm[0].keys(), expected | std::views::elements<0>));
+      LIBCPP_ASSERT(std::ranges::equal(vm[0], expected));
+      assert(vm[0].keys().get_allocator().resource() == &mr);
+      assert(vm[0].values().get_allocator().resource() == &mr);
+    }
+    {
+      using M = std::flat_map<int, short, std::less<int>, std::pmr::vector<int>, std::pmr::vector<short>>;
+      using R = std::ranges::subrange<const P*>;
+      std::pmr::monotonic_buffer_resource mr;
+      std::pmr::vector<M> vm(&mr);
+      vm.emplace_back(std::from_range, R(ar, ar));
+      assert(vm[0].empty());
+      assert(vm[0].keys().get_allocator().resource() == &mr);
+      assert(vm[0].values().get_allocator().resource() == &mr);
+    }
+  }
+  {
+    // flat_map(sorted_unique_t, const key_container_type& key_cont,
+    //          const mapped_container_type& mapped_cont, const Alloc& a);
+    using M = std::flat_map<int, int, std::less<int>, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    std::pmr::vector<int> ks = {1, 2, 4, 10};
+    std::pmr::vector<int> vs = {4, 3, 2, 1};
+    vm.emplace_back(std::sorted_unique, ks, vs);
+    assert(!ks.empty()); // it was an lvalue above
+    assert(!vs.empty()); // it was an lvalue above
+    assert((vm[0] == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    // flat_map(sorted_unique_t, const key_container_type& key_cont,
+    //          const mapped_container_type& mapped_cont, const Alloc& a);
+    using M = std::flat_map<int, int, std::less<int>, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    std::pmr::vector<int> ks({1, 2, 4, 10}, &mr);
+    std::pmr::vector<int> vs({4, 3, 2, 1}, &mr);
+    vm.emplace_back(std::sorted_unique, ks, vs);
+    assert((vm[0] == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type> il, const Alloc& a);
+    // cpp_17
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    using P = std::pair<int, int>;
+    P ar[]  = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    vm.emplace_back(
+        std::sorted_unique, cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 4), C(3));
+    assert((vm[0] == M{{1, 1}, {2, 2}, {4, 4}, {5, 5}}));
+    assert(vm[0].key_comp() == C(3));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type> il, const Alloc& a);
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    std::pair<int, int> ar[1] = {{42, 42}};
+    vm.emplace_back(std::sorted_unique, ar, ar, C(4));
+    assert(vm[0] == M{});
+    assert(vm[0].key_comp() == C(4));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    // flat_map(InputIterator first, InputIterator last, const Alloc& a);
+    // cpp_17
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    using P = std::pair<int, int>;
+    P ar[]  = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    vm.emplace_back(
+        std::sorted_unique, cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 4), C(3));
+    assert((vm[0] == M{{1, 1}, {2, 2}, {4, 4}, {5, 5}}));
+    assert(vm[0].key_comp() == C(3));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+  {
+    // flat_map(InputIterator first, InputIterator last, const Alloc& a);
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::pmr::vector<int>, std::pmr::vector<int>>;
+    std::pmr::monotonic_buffer_resource mr;
+    std::pmr::vector<M> vm(&mr);
+    std::pair<int, int> ar[1] = {{42, 42}};
+    vm.emplace_back(std::sorted_unique, ar, ar, C(4));
+    assert(vm[0] == M{});
+    assert(vm[0].key_comp() == C(4));
+    assert(vm[0].keys().get_allocator().resource() == &mr);
+    assert(vm[0].values().get_allocator().resource() == &mr);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/range.pass.cpp

@@ -0,0 +1,227 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<container-compatible-range<value_type> R>
+//     flat_map(from_range_t, R&&)
+// template<container-compatible-range<value_type> R>
+//     flat_map(from_range_t, R&&, const key_compare&)
+// template<container-compatible-range<value_type> R, class Alloc>
+//      flat_map(from_range_t, R&&, const Alloc&);
+// template<container-compatible-range<value_type> R, class Alloc>
+//      flat_map(from_range_t, R&&, const key_compare&, const Alloc&);
+
+#include <algorithm>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <string>
+#include <vector>
+
+#include "min_allocator.h"
+#include "test_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+
+// test constraint container-compatible-range
+
+template <class V>
+using RangeOf = std::ranges::subrange<V*>;
+using Map     = std::flat_map<int, double>;
+
+static_assert(std::is_constructible_v<Map, std::from_range_t, RangeOf<std::pair<int, double>>>);
+static_assert(std::is_constructible_v<Map, std::from_range_t, RangeOf<std::pair<short, double>>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<int>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<double>>);
+
+static_assert(std::is_constructible_v<Map, std::from_range_t, RangeOf<std::pair<int, double>>, std::less<int>>);
+static_assert(std::is_constructible_v<Map, std::from_range_t, RangeOf<std::pair<short, double>>, std::less<int>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<int>, std::less<int>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<double>, std::less<int>>);
+
+static_assert(std::is_constructible_v<Map, std::from_range_t, RangeOf<std::pair<int, double>>, std::allocator<int>>);
+static_assert(std::is_constructible_v<Map, std::from_range_t, RangeOf<std::pair<short, double>>, std::allocator<int>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<int>, std::allocator<int>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<double>, std::allocator<int>>);
+
+static_assert(std::is_constructible_v<Map,
+                                      std::from_range_t,
+                                      RangeOf<std::pair<int, double>>,
+                                      std::less<int>,
+                                      std::allocator<int>>);
+static_assert(std::is_constructible_v<Map,
+                                      std::from_range_t,
+                                      RangeOf<std::pair<short, double>>,
+                                      std::less<int>,
+                                      std::allocator<int>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<int>, std::less<int>, std::allocator<int>>);
+static_assert(!std::is_constructible_v<Map, std::from_range_t, RangeOf<double>, std::less<int>, std::allocator<int>>);
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    static_assert(std::is_constructible_v<M1, std::from_range_t, M1, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::from_range_t, M1, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::from_range_t, M2, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::from_range_t, M3, const A2&>);
+
+    static_assert(std::is_constructible_v<M1, std::from_range_t, M1, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::from_range_t, M1, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::from_range_t, M2, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::from_range_t, M3, const C&, const A2&>);
+  }
+  {
+    // container-compatible-range
+    using C           = test_less<int>;
+    using A1          = test_allocator<int>;
+    using A2          = test_allocator<std::string>;
+    using M           = std::flat_map<int, std::string, C, std::vector<int, A1>, std::vector<std::string, A2>>;
+    using Pair        = std::pair<int, std::string>;
+    using PairLike    = std::tuple<int, std::string>;
+    using NonPairLike = int;
+
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<Pair>&>);
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<PairLike>&>);
+    static_assert(!std::is_constructible_v<M, std::from_range_t, std::vector<NonPairLike>&>);
+
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<Pair>&, const C&>);
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<PairLike>&, const C&>);
+    static_assert(!std::is_constructible_v<M, std::from_range_t, std::vector<NonPairLike>&, const C&>);
+
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<Pair>&, const A1&>);
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<PairLike>&, const A1&>);
+    static_assert(!std::is_constructible_v<M, std::from_range_t, std::vector<NonPairLike>&, const A1&>);
+
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<Pair>&, const C&, const A1&>);
+    static_assert(std::is_constructible_v<M, std::from_range_t, std::vector<PairLike>&, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M, std::from_range_t, std::vector<NonPairLike>&, const C&, const A1&>);
+  }
+
+  using P      = std::pair<int, short>;
+  P ar[]       = {{1, 1}, {1, 2}, {1, 3}, {2, 4}, {2, 5}, {3, 6}, {2, 7}, {3, 8}, {3, 9}};
+  P expected[] = {{1, 1}, {2, 4}, {3, 6}};
+  {
+    // flat_map(from_range_t, R&&)
+    // input_range && !common
+    using M    = std::flat_map<int, short>;
+    using Iter = cpp20_input_iterator<const P*>;
+    using Sent = sentinel_wrapper<Iter>;
+    using R    = std::ranges::subrange<Iter, Sent>;
+    auto m     = M(std::from_range, R(Iter(ar), Sent(Iter(ar + 9))));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+
+    // explicit(false)
+    M m2 = {std::from_range, R(Iter(ar), Sent(Iter(ar + 9)))};
+    assert(m2 == m);
+  }
+  {
+    // flat_map(from_range_t, R&&)
+    // greater
+    using M    = std::flat_map<int, short, std::greater<int>, std::deque<int, min_allocator<int>>, std::deque<short>>;
+    using Iter = cpp20_input_iterator<const P*>;
+    using Sent = sentinel_wrapper<Iter>;
+    using R    = std::ranges::subrange<Iter, Sent>;
+    auto m     = M(std::from_range, R(Iter(ar), Sent(Iter(ar + 9))));
+    assert((m.keys() == std::deque<int, min_allocator<int>>{3, 2, 1}));
+    LIBCPP_ASSERT((m.values() == std::deque<short>{6, 4, 1}));
+  }
+  {
+    // flat_map(from_range_t, R&&)
+    // contiguous range
+    using M = std::flat_map<int, short>;
+    using R = std::ranges::subrange<const P*>;
+    auto m  = M(std::from_range, R(ar, ar + 9));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+  }
+  {
+    // flat_map(from_range_t, R&&, const key_compare&)
+    using C = test_less<int>;
+    using M = std::flat_map<int, short, C, std::vector<int>, std::deque<short>>;
+    using R = std::ranges::subrange<const P*>;
+    auto m  = M(std::from_range, R(ar, ar + 9), C(3));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.key_comp() == C(3));
+
+    // explicit(false)
+    M m2 = {std::from_range, R(ar, ar + 9), C(3)};
+    assert(m2 == m);
+    assert(m2.key_comp() == C(3));
+  }
+  {
+    // flat_map(from_range_t, R&&, const Allocator&)
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, std::less<int>, std::vector<int, A1>, std::deque<short, A2>>;
+    using R  = std::ranges::subrange<const P*>;
+    auto m   = M(std::from_range, R(ar, ar + 9), A1(5));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(from_range_t, R&&, const Allocator&)
+    // explicit(false)
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, std::less<int>, std::vector<int, A1>, std::deque<short, A2>>;
+    using R  = std::ranges::subrange<const P*>;
+    M m      = {std::from_range, R(ar, ar + 9), A1(5)}; // implicit ctor
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(from_range_t, R&&, const key_compare&, const Allocator&)
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, C, std::vector<int, A1>, std::deque<short, A2>>;
+    using R  = std::ranges::subrange<const P*>;
+    auto m   = M(std::from_range, R(ar, ar + 9), C(3), A1(5));
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.key_comp() == C(3));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(from_range_t, R&&, const key_compare&, const Allocator&)
+    // explicit(false)
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, std::less<int>, std::deque<int, A1>, std::vector<short, A2>>;
+    using R  = std::ranges::subrange<const P*>;
+    M m      = {std::from_range, R(ar, ar + 9), {}, A2(5)}; // implicit ctor
+    assert(std::ranges::equal(m.keys(), expected | std::views::elements<0>));
+    LIBCPP_ASSERT(std::ranges::equal(m, expected));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/sorted_container.pass.cpp

@@ -0,0 +1,165 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map(sorted_unique_t, key_container_type key_cont, mapped_container_type mapped_cont,
+//          const key_compare& comp = key_compare());
+//
+// template<class Alloc>
+//   flat_map(sorted_unique_t, const key_container_type& key_cont,
+//            const mapped_container_type& mapped_cont, const Alloc& a);
+// template<class Alloc>
+//   flat_map(sorted_unique_t, const key_container_type& key_cont,
+//            const mapped_container_type& mapped_cont,
+//            const key_compare& comp, const Alloc& a);
+
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "min_allocator.h"
+#include "MoveOnly.h"
+#include "test_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    static_assert(std::is_constructible_v<M1, std::sorted_unique_t, const V1&, const V1&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::sorted_unique_t, const V1&, const V1&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::sorted_unique_t, const V1&, const V2&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::sorted_unique_t, const V2&, const V1&, const A2&>);
+
+    static_assert(std::is_constructible_v<M1, std::sorted_unique_t, const V1&, const V1&, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::sorted_unique_t, const V1&, const V1&, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::sorted_unique_t, const V1&, const V2&, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::sorted_unique_t, const V2&, const V1&, const C&, const A2&>);
+  }
+  {
+    // flat_map(sorted_unique_t, key_container_type , mapped_container_type)
+    using M              = std::flat_map<int, char>;
+    std::vector<int> ks  = {1, 2, 4, 10};
+    std::vector<char> vs = {4, 3, 2, 1};
+    auto ks2             = ks;
+    auto vs2             = vs;
+
+    auto m = M(std::sorted_unique, ks, vs);
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    m = M(std::sorted_unique, std::move(ks), std::move(vs));
+    assert(ks.empty()); // it was moved-from
+    assert(vs.empty()); // it was moved-from
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, std::move(ks2), std::move(vs2)};
+    assert(m == m2);
+  }
+  {
+    // flat_map(sorted_unique_t, key_container_type , mapped_container_type)
+    // non-default container, comparator and allocator type
+    using Ks = std::deque<int, min_allocator<int>>;
+    using Vs = std::deque<char, min_allocator<char>>;
+    using M  = std::flat_map<int, char, std::greater<int>, Ks, Vs>;
+    Ks ks    = {10, 4, 2, 1};
+    Vs vs    = {1, 2, 3, 4};
+    auto m   = M(std::sorted_unique, ks, vs);
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    m = M(std::sorted_unique, std::move(ks), std::move(vs));
+    assert(ks.empty()); // it was moved-from
+    assert(vs.empty()); // it was moved-from
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+  }
+  {
+    // flat_map(sorted_unique_t, key_container_type , mapped_container_type)
+    // allocator copied into the containers
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, std::less<int>, std::vector<int, A>, std::deque<int, A>>;
+    auto ks = std::vector<int, A>({1, 2, 4, 10}, A(4));
+    auto vs = std::deque<int, A>({4, 3, 2, 1}, A(5));
+    auto m  = M(std::sorted_unique, std::move(ks), std::move(vs));
+    assert(ks.empty()); // it was moved-from
+    assert(vs.empty()); // it was moved-from
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    assert(m.keys().get_allocator() == A(4));
+    assert(m.values().get_allocator() == A(5));
+  }
+  {
+    // flat_map(sorted_unique_t, key_container_type , mapped_container_type, key_compare)
+    using C              = test_less<int>;
+    using M              = std::flat_map<int, char, C>;
+    std::vector<int> ks  = {1, 2, 4, 10};
+    std::vector<char> vs = {4, 3, 2, 1};
+
+    auto m = M(std::sorted_unique, ks, vs, C(4));
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    assert(m.key_comp() == C(4));
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, ks, vs, C(4)};
+    assert(m2 == m);
+    assert(m2.key_comp() == C(4));
+  }
+  {
+    // flat_map(sorted_unique_t, key_container_type , mapped_container_type, key_compare, const Allocator&)
+    using C                = test_less<int>;
+    using A                = test_allocator<int>;
+    using M                = std::flat_map<int, int, C, std::vector<int, A>, std::vector<int, A>>;
+    std::vector<int, A> ks = {1, 2, 4, 10};
+    std::vector<int, A> vs = {4, 3, 2, 1};
+    auto m                 = M(std::sorted_unique, ks, vs, C(4), A(5));
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    assert(m.key_comp() == C(4));
+    assert(m.keys().get_allocator() == A(5));
+    assert(m.values().get_allocator() == A(5));
+
+    // explicit(false)
+    M m2 = {ks, vs, C(4), A(5)};
+    assert(m2 == m);
+    assert(m2.key_comp() == C(4));
+    assert(m2.keys().get_allocator() == A(5));
+    assert(m2.values().get_allocator() == A(5));
+  }
+  {
+    // flat_map(sorted_unique_t, key_container_type , mapped_container_type, const Allocator&)
+    using A = test_allocator<int>;
+    using M = std::flat_map<int, int, std::less<int>, std::vector<int, A>, std::deque<int, A>>;
+    auto ks = std::vector<int, A>({1, 2, 4, 10}, A(4));
+    auto vs = std::deque<int, A>({4, 3, 2, 1}, A(5));
+    auto m  = M(std::sorted_unique, ks, vs, A(6)); // replaces the allocators
+    assert(!ks.empty());                           // it was an lvalue above
+    assert(!vs.empty());                           // it was an lvalue above
+    assert((m == M{{1, 4}, {2, 3}, {4, 2}, {10, 1}}));
+    assert(m.keys().get_allocator() == A(6));
+    assert(m.values().get_allocator() == A(6));
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, ks, vs, A(6)};
+    assert(m2 == m);
+    assert(m2.keys().get_allocator() == A(6));
+    assert(m2.values().get_allocator() == A(6));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/sorted_initializer_list.pass.cpp

@@ -0,0 +1,179 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template <class InputIterator>
+//   flat_map(sorted_unique_t s, initializer_list<value_type> il,
+//            const key_compare& comp = key_compare())
+// template<class Alloc>
+//   flat_map(sorted_unique_t, initializer_list<value_type> il, const Alloc& a);
+// template<class Alloc>
+//   flat_map(sorted_unique_t, initializer_list<value_type> il,
+//            const key_compare& comp, const Alloc& a);
+
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "min_allocator.h"
+#include "test_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+
+template <class T, class U>
+std::initializer_list<std::pair<T, U>> il = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+
+const auto il1 = il<int, int>;
+const auto il2 = il<int, short>;
+const auto il3 = il<short, int>;
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = other_allocator<int>;
+    using V1 = std::vector<int, A1>;
+    using V2 = std::vector<int, A2>;
+    using M1 = std::flat_map<int, int, C, V1, V1>;
+    using M2 = std::flat_map<int, int, C, V1, V2>;
+    using M3 = std::flat_map<int, int, C, V2, V1>;
+    using IL = std::initializer_list<std::pair<int, int>>;
+    static_assert(std::is_constructible_v<M1, std::sorted_unique_t, IL, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::sorted_unique_t, IL, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::sorted_unique_t, IL, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::sorted_unique_t, IL, const A2&>);
+
+    static_assert(std::is_constructible_v<M1, std::sorted_unique_t, IL, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::sorted_unique_t, IL, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::sorted_unique_t, IL, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::sorted_unique_t, IL, const C&, const A2&>);
+  }
+  {
+    // initializer_list<value_type> needs to match exactly
+    using M = std::flat_map<int, short>;
+    using C = typename M::key_compare;
+    static_assert(std::is_constructible_v<M, std::sorted_unique_t, std::initializer_list<std::pair<int, short>>>);
+    static_assert(std::is_constructible_v<M, std::sorted_unique_t, std::initializer_list<std::pair<int, short>>, C>);
+    static_assert(std::is_constructible_v<M,
+                                          std::sorted_unique_t,
+                                          std::initializer_list<std::pair<int, short>>,
+                                          C,
+                                          std::allocator<int>>);
+    static_assert(std::is_constructible_v<M,
+                                          std::sorted_unique_t,
+                                          std::initializer_list<std::pair<int, short>>,
+                                          std::allocator<int>>);
+    static_assert(
+        !std::is_constructible_v<M, std::sorted_unique_t, std::initializer_list<std::pair<const int, short>>>);
+    static_assert(
+        !std::is_constructible_v<M, std::sorted_unique_t, std::initializer_list<std::pair<const int, short>>, C>);
+    static_assert(!std::is_constructible_v<M,
+                                           std::sorted_unique_t,
+                                           std::initializer_list<std::pair<const int, short>>,
+                                           C,
+                                           std::allocator<int>>);
+    static_assert(!std::is_constructible_v<M,
+                                           std::sorted_unique_t,
+                                           std::initializer_list<std::pair<const int, short>>,
+                                           std::allocator<int>>);
+    static_assert(
+        !std::is_constructible_v<M, std::sorted_unique_t, std::initializer_list<std::pair<const int, const short>>>);
+    static_assert(
+        !std::is_constructible_v<M, std::sorted_unique_t, std::initializer_list<std::pair<const int, const short>>, C>);
+    static_assert(!std::is_constructible_v<M,
+                                           std::sorted_unique_t,
+                                           std::initializer_list<std::pair<const int, const short>>,
+                                           C,
+                                           std::allocator<int>>);
+    static_assert(!std::is_constructible_v<M,
+                                           std::sorted_unique_t,
+                                           std::initializer_list<std::pair<const int, const short>>,
+                                           std::allocator<int>>);
+  }
+
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type>);
+    using M       = std::flat_map<int, int>;
+    auto m        = M(std::sorted_unique, il1);
+    auto expected = M{{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    assert(m == expected);
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, il1};
+    assert(m2 == m);
+  }
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type>, const key_compare&);
+    using M = std::flat_map<int, int, std::function<bool(int, int)>>;
+    auto m  = M(std::sorted_unique, il1, std::less<int>());
+    assert(m == M({{1, 1}, {2, 2}, {4, 4}, {5, 5}}, std::less<>()));
+    assert(m.key_comp()(1, 2) == true);
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, il1, std::less<int>()};
+    assert(m2 == m);
+  }
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type>, const key_compare&);
+    // greater
+    using M = std::flat_map<int, int, std::greater<int>, std::deque<int, min_allocator<int>>, std::vector<int>>;
+    std::initializer_list<std::pair<int, int>> il4{{5, 5}, {4, 4}, {2, 2}, {1, 1}};
+    auto m = M(std::sorted_unique, il4, std::greater<int>());
+    assert((m == M{{5, 5}, {4, 4}, {2, 2}, {1, 1}}));
+  }
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type>,  const Allocator&)
+    using A1      = test_allocator<int>;
+    using A2      = test_allocator<short>;
+    using M       = std::flat_map<int, short, std::less<int>, std::vector<int, A1>, std::deque<short, A2>>;
+    auto m        = M(std::sorted_unique, il2, A1(5));
+    auto expected = M{{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    assert(m == expected);
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, il2, A1(5)};
+    assert(m2 == m);
+    assert(m2.keys().get_allocator() == A1(5));
+    assert(m2.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type>, const key_compare&, const Allocator&);
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, C, std::vector<int, A1>, std::deque<short, A2>>;
+    auto m   = M(std::sorted_unique, il2, C(3), A1(5));
+    assert((m == M{{1, 1}, {2, 2}, {4, 4}, {5, 5}}));
+    assert(m.key_comp() == C(3));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(sorted_unique_t, initializer_list<value_type>, const key_compare&, const Allocator&);
+    // explicit(false)
+    using A1 = test_allocator<short>;
+    using A2 = test_allocator<int>;
+    using M  = std::flat_map<short, int, std::less<int>, std::deque<short, A1>, std::vector<int, A2>>;
+    M m      = {std::sorted_unique, il3, {}, A1(5)}; // implicit ctor
+    assert((m == M{{1, 1}, {2, 2}, {4, 4}, {5, 5}}));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.cons/sorted_iter_iter.pass.cpp

@@ -0,0 +1,171 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template <class InputIterator>
+//   flat_map(sorted_unique_t, InputIterator first, InputIterator last, const key_compare& comp = key_compare());
+// template<class InputIterator, class Alloc>
+//   flat_map(InputIterator first, InputIterator last, const Alloc& a);
+// template<class InputIterator, class Allocator>
+//   flat_map(sorted_unique_t, InputIterator first, InputIterator last, const key_compare& comp, const Allocator& a);
+
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "min_allocator.h"
+#include "test_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+#include "../../../test_compare.h"
+
+int main(int, char**) {
+  {
+    // The constructors in this subclause shall not participate in overload
+    // resolution unless uses_allocator_v<key_container_type, Alloc> is true
+    // and uses_allocator_v<mapped_container_type, Alloc> is true.
+    using C     = test_less<int>;
+    using A1    = test_allocator<int>;
+    using A2    = other_allocator<int>;
+    using V1    = std::vector<int, A1>;
+    using V2    = std::vector<int, A2>;
+    using M1    = std::flat_map<int, int, C, V1, V1>;
+    using M2    = std::flat_map<int, int, C, V1, V2>;
+    using M3    = std::flat_map<int, int, C, V2, V1>;
+    using Iter1 = typename M1::iterator;
+    using Iter2 = typename M2::iterator;
+    using Iter3 = typename M3::iterator;
+    static_assert(std::is_constructible_v<M1, std::sorted_unique_t, Iter1, Iter1, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::sorted_unique_t, Iter1, Iter1, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::sorted_unique_t, Iter2, Iter2, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::sorted_unique_t, Iter3, Iter3, const A2&>);
+
+    static_assert(std::is_constructible_v<M1, std::sorted_unique_t, Iter1, Iter1, const C&, const A1&>);
+    static_assert(!std::is_constructible_v<M1, std::sorted_unique_t, Iter1, Iter1, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M2, std::sorted_unique_t, Iter2, Iter2, const C&, const A2&>);
+    static_assert(!std::is_constructible_v<M3, std::sorted_unique_t, Iter3, Iter3, const C&, const A2&>);
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator, InputIterator);
+    // cpp17_input_iterator
+    using M       = std::flat_map<int, int>;
+    using P       = std::pair<int, int>;
+    P ar[]        = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    auto m        = M(std::sorted_unique, cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 4));
+    auto expected = M{{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    assert(m == expected);
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, cpp17_input_iterator<const P*>(ar), cpp17_input_iterator<const P*>(ar + 4)};
+    assert(m2 == m);
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator, InputIterator);
+    // contiguous iterator
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>;
+    std::pair<int, int> ar[] = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    auto m                   = M(std::sorted_unique, ar, ar + 4);
+    auto expected            = M{{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    assert(m == expected);
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator, InputIterator, const key_compare&);
+    // cpp_17_input_iterator
+    using M = std::flat_map<int, int, std::function<bool(int, int)>>;
+    using P = std::pair<int, int>;
+    P ar[]  = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    auto m  = M(std::sorted_unique,
+               cpp17_input_iterator<const P*>(ar),
+               cpp17_input_iterator<const P*>(ar + 4),
+               std::less<int>());
+    assert(m == M({{1, 1}, {2, 2}, {4, 4}, {5, 5}}, std::less<>()));
+    assert(m.key_comp()(1, 2) == true);
+
+    // explicit(false)
+    M m2 = {std::sorted_unique,
+            cpp17_input_iterator<const P*>(ar),
+            cpp17_input_iterator<const P*>(ar + 4),
+            std::less<int>()};
+    assert(m2 == m);
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator, InputIterator, const key_compare&);
+    // greater
+    using M = std::flat_map<int, int, std::greater<int>, std::deque<int, min_allocator<int>>, std::vector<int>>;
+    using P = std::pair<int, int>;
+    P ar[]  = {{5, 5}, {4, 4}, {2, 2}, {1, 1}};
+    auto m  = M(std::sorted_unique,
+               cpp17_input_iterator<const P*>(ar),
+               cpp17_input_iterator<const P*>(ar + 4),
+               std::greater<int>());
+    assert((m == M{{5, 5}, {4, 4}, {2, 2}, {1, 1}}));
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator, InputIterator, const key_compare&);
+    // contiguous iterator
+    using C = test_less<int>;
+    using M = std::flat_map<int, int, C, std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>;
+    std::pair<int, int> ar[1] = {{42, 42}};
+    auto m                    = M(std::sorted_unique, ar, ar, C(5));
+    assert(m.empty());
+    assert(m.key_comp() == C(5));
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator , InputIterator, const Allocator&)
+    using A1      = test_allocator<int>;
+    using A2      = test_allocator<short>;
+    using M       = std::flat_map<int, short, std::less<int>, std::vector<int, A1>, std::deque<short, A2>>;
+    using P       = std::pair<int, int>;
+    P ar[]        = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    auto m        = M(std::sorted_unique, ar, ar + 4, A1(5));
+    auto expected = M{{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    assert(m == expected);
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+
+    // explicit(false)
+    M m2 = {std::sorted_unique, ar, ar + 4, A1(5)};
+    assert(m2 == m);
+    assert(m2.keys().get_allocator() == A1(5));
+    assert(m2.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator, InputIterator, const key_compare&, const Allocator&);
+    using C  = test_less<int>;
+    using A1 = test_allocator<int>;
+    using A2 = test_allocator<short>;
+    using M  = std::flat_map<int, short, C, std::vector<int, A1>, std::deque<short, A2>>;
+    using P  = std::pair<int, int>;
+    P ar[]   = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    auto m   = M(std::sorted_unique, ar, ar + 4, C(3), A1(5));
+    assert((m == M{{1, 1}, {2, 2}, {4, 4}, {5, 5}}));
+    assert(m.key_comp() == C(3));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+  {
+    // flat_map(sorted_unique_t, InputIterator, InputIterator, const key_compare&, const Allocator&);
+    // explicit(false)
+    using A1 = test_allocator<short>;
+    using A2 = test_allocator<int>;
+    using M  = std::flat_map<short, int, std::less<int>, std::deque<short, A1>, std::vector<int, A2>>;
+    using P  = std::pair<int, int>;
+    P ar[]   = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    M m      = {std::sorted_unique, ar, ar + 4, {}, A1(5)}; // implicit ctor
+    assert((m == M{{1, 1}, {2, 2}, {4, 4}, {5, 5}}));
+    assert(m.keys().get_allocator() == A1(5));
+    assert(m.values().get_allocator() == A2(5));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.erasure/erase_if.pass.cpp

@@ -0,0 +1,93 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class Key, class T, class Compare, class KeyContainer, class MappedContainer, class Predicate>
+//   typename flat_map<Key, T, Compare, KeyContainer, MappedContainer>::size_type
+//   erase_if(flat_map<Key, T, Compare, KeyContainer, MappedContainer>& c, Predicate pred);
+
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <initializer_list>
+#include <vector>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+// Verify that `flat_map` (like `map`) does NOT support std::erase.
+//
+template <class S>
+concept HasStdErase = requires(S& s, typename S::value_type x) { std::erase(s, x); };
+static_assert(HasStdErase<std::vector<int>>);
+static_assert(!HasStdErase<std::flat_map<int, int>>);
+
+template <class M>
+M make(std::initializer_list<int> vals) {
+  M ret;
+  for (int v : vals)
+    ret[static_cast<typename M::key_type>(v)] = static_cast<typename M::mapped_type>(v + 10);
+  return ret;
+}
+
+template <class M, class Pred>
+void test0(
+    std::initializer_list<int> vals, Pred p, std::initializer_list<int> expected, std::size_t expected_erased_count) {
+  M s = make<M>(vals);
+  ASSERT_SAME_TYPE(typename M::size_type, decltype(std::erase_if(s, p)));
+  assert(expected_erased_count == std::erase_if(s, p));
+  assert(s == make<M>(expected));
+}
+
+template <class S>
+void test() {
+  // Test all the plausible signatures for this predicate.
+  auto is1   = [](typename S::const_reference v) { return v.first == 1; };
+  auto is2   = [](typename S::value_type v) { return v.first == 2; };
+  auto is3   = [](const typename S::value_type& v) { return v.first == 3; };
+  auto is4   = [](auto v) { return v.first == 4; };
+  auto True  = [](const auto&) { return true; };
+  auto False = [](auto&&) { return false; };
+
+  test0<S>({}, is1, {}, 0);
+
+  test0<S>({1}, is1, {}, 1);
+  test0<S>({1}, is2, {1}, 0);
+
+  test0<S>({1, 2}, is1, {2}, 1);
+  test0<S>({1, 2}, is2, {1}, 1);
+  test0<S>({1, 2}, is3, {1, 2}, 0);
+
+  test0<S>({1, 2, 3}, is1, {2, 3}, 1);
+  test0<S>({1, 2, 3}, is2, {1, 3}, 1);
+  test0<S>({1, 2, 3}, is3, {1, 2}, 1);
+  test0<S>({1, 2, 3}, is4, {1, 2, 3}, 0);
+
+  test0<S>({1, 2, 3}, True, {}, 3);
+  test0<S>({1, 2, 3}, False, {1, 2, 3}, 0);
+}
+
+int main(int, char**) {
+  test<std::flat_map<int, char>>();
+  test<std::flat_map<int,
+                     char,
+                     std::less<int>,
+                     std::vector<int, min_allocator<int>>,
+                     std::vector<char, min_allocator<char>>>>();
+  test<std::flat_map<int, char, std::greater<int>, std::vector<int, test_allocator<int>>>>();
+  test<std::flat_map<int, char, std::less<int>, std::deque<int, min_allocator<int>>>>();
+  test<std::flat_map<int, char, std::greater<int>, std::deque<int, test_allocator<int>>>>();
+  test<std::flat_map<long, int>>();
+  test<std::flat_map<double, int>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.erasure/erase_if_exceptions.pass.cpp

@@ -0,0 +1,155 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: no-exceptions
+
+// <flat_map>
+
+// template<class Key, class T, class Compare, class KeyContainer, class MappedContainer, class Predicate>
+//   typename flat_map<Key, T, Compare, KeyContainer, MappedContainer>::size_type
+//   erase_if(flat_map<Key, T, Compare, KeyContainer, MappedContainer>& c, Predicate pred);
+// If any member function in [flat.set.defn] exits via an exception, the invariant is restored.
+// (This is not a member function, but let's respect the invariant anyway.)
+
+#include <algorithm>
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "../helpers.h"
+#include "test_macros.h"
+
+struct Counter {
+  int c1, c2, throws;
+  void tick() {
+    c1 -= 1;
+    if (c1 == 0) {
+      c1 = c2;
+      throws += 1;
+      throw 42;
+    }
+  }
+};
+Counter g_counter = {0, 0, 0};
+
+struct ThrowingAssignment {
+  ThrowingAssignment(int i) : i_(i) {}
+  ThrowingAssignment(const ThrowingAssignment&) = default;
+  ThrowingAssignment& operator=(const ThrowingAssignment& rhs) {
+    g_counter.tick();
+    i_ = rhs.i_;
+    g_counter.tick();
+    return *this;
+  }
+  operator int() const { return i_; }
+  int i_;
+};
+
+struct ThrowingComparator {
+  bool operator()(const ThrowingAssignment& a, const ThrowingAssignment& b) const {
+    g_counter.tick();
+    return a.i_ < b.i_;
+  }
+};
+
+struct ErasurePredicate {
+  bool operator()(const auto& x) const { return (3 <= x.first && x.first <= 5); }
+};
+
+int main(int, char**) {
+  const std::pair<int, int> expected[] = {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}, {8, 8}};
+  {
+    using M = std::flat_map<ThrowingAssignment, int, ThrowingComparator>;
+    for (int first_throw = 1; first_throw < 99; ++first_throw) {
+      for (int second_throw = 1; second_throw < 99; ++second_throw) {
+        g_counter = {0, 0, 0};
+        M m       = M({1, 2, 3, 4, 5, 6, 7, 8}, {1, 2, 3, 4, 5, 6, 7, 8});
+        try {
+          g_counter = {first_throw, second_throw, 0};
+          auto n    = std::erase_if(m, ErasurePredicate());
+          assert(n == 3);
+          // If it didn't throw at all, we're done.
+          g_counter = {0, 0, 0};
+          assert((m == M{{1, 1}, {2, 2}, {6, 6}, {7, 7}, {8, 8}}));
+          first_throw = 99; // "done"
+          break;
+        } catch (int ex) {
+          assert(ex == 42);
+          check_invariant(m);
+          LIBCPP_ASSERT(m.empty() || std::equal(m.begin(), m.end(), expected, expected + 8));
+          if (g_counter.throws == 1) {
+            // We reached the first throw but not the second throw.
+            break;
+          }
+        }
+      }
+    }
+  }
+  {
+    using M = std::flat_map<int, ThrowingAssignment, ThrowingComparator>;
+    for (int first_throw = 1; first_throw < 99; ++first_throw) {
+      for (int second_throw = 1; second_throw < 99; ++second_throw) {
+        g_counter = {0, 0, 0};
+        M m       = M({1, 2, 3, 4, 5, 6, 7, 8}, {1, 2, 3, 4, 5, 6, 7, 8});
+        try {
+          g_counter = {first_throw, second_throw, 0};
+          auto n    = std::erase_if(m, ErasurePredicate());
+          assert(n == 3);
+          // If it didn't throw at all, we're done.
+          g_counter = {0, 0, 0};
+          assert((m == M{{1, 1}, {2, 2}, {6, 6}, {7, 7}, {8, 8}}));
+          first_throw = 99; // "done"
+          break;
+        } catch (int ex) {
+          assert(ex == 42);
+          check_invariant(m);
+          LIBCPP_ASSERT(m.empty() || std::equal(m.begin(), m.end(), expected, expected + 8));
+          if (g_counter.throws == 1) {
+            // We reached the first throw but not the second throw.
+            break;
+          }
+        }
+      }
+    }
+  }
+  {
+    using M =
+        std::flat_map<ThrowingAssignment, int, ThrowingComparator, std::deque<ThrowingAssignment>, std::deque<int>>;
+    for (int first_throw = 1; first_throw < 99; ++first_throw) {
+      for (int second_throw = 1; second_throw < 99; ++second_throw) {
+        g_counter                                = {0, 0, 0};
+        std::deque<ThrowingAssignment> container = {5, 6, 7, 8};
+        container.insert(container.begin(), {1, 2, 3, 4});
+        M m = M(std::move(container), {1, 2, 3, 4, 5, 6, 7, 8});
+        try {
+          g_counter = {first_throw, second_throw, 0};
+          auto n    = std::erase_if(m, ErasurePredicate());
+          assert(n == 3);
+          // If it didn't throw at all, we're done.
+          g_counter = {0, 0, 0};
+          assert((m == M{{1, 1}, {2, 2}, {6, 6}, {7, 7}, {8, 8}}));
+          first_throw = 99; // "done"
+          break;
+        } catch (int ex) {
+          assert(ex == 42);
+          check_invariant(m);
+          LIBCPP_ASSERT(m.empty() || std::equal(m.begin(), m.end(), expected, expected + 8));
+          if (g_counter.throws == 1) {
+            // We reached the first throw but not the second throw.
+            break;
+          }
+        }
+      }
+    }
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.iterators/iterator.pass.cpp

@@ -0,0 +1,96 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+//       iterator begin()   noexcept;
+// const_iterator begin()   const noexcept
+//       iterator end()     noexcept;
+// const_iterator end()     const noexcept;
+//
+// const_iterator cbegin()  const noexcept;
+// const_iterator cend()    const noexcept;
+
+#include <cassert>
+#include <cstddef>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <string>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  M m         = {{1, 'a'}, {2, 'b'}, {3, 'c'}, {4, 'd'}};
+  const M& cm = m;
+  ASSERT_SAME_TYPE(decltype(m.begin()), typename M::iterator);
+  ASSERT_SAME_TYPE(decltype(m.cbegin()), typename M::const_iterator);
+  ASSERT_SAME_TYPE(decltype(cm.begin()), typename M::const_iterator);
+  ASSERT_SAME_TYPE(decltype(m.end()), typename M::iterator);
+  ASSERT_SAME_TYPE(decltype(m.cend()), typename M::const_iterator);
+  ASSERT_SAME_TYPE(decltype(cm.end()), typename M::const_iterator);
+  static_assert(noexcept(m.begin()));
+  static_assert(noexcept(cm.begin()));
+  static_assert(noexcept(m.cbegin()));
+  static_assert(noexcept(m.end()));
+  static_assert(noexcept(cm.end()));
+  static_assert(noexcept(m.cend()));
+  assert(m.size() == 4);
+  assert(std::distance(m.begin(), m.end()) == 4);
+  assert(std::distance(cm.begin(), cm.end()) == 4);
+  assert(std::distance(m.cbegin(), m.cend()) == 4);
+  typename M::iterator i;                   // default-construct
+  i                            = m.begin(); // move-assignment
+  typename M::const_iterator k = i;         // converting constructor
+  assert(i == k);                           // comparison
+  for (int j = 1; j <= 4; ++j, ++i) {       // pre-increment
+    assert(i->first == j);                  // operator->
+    assert(i->second == 'a' + j - 1);
+  }
+  assert(i == m.end());
+  for (int j = 4; j >= 1; --j) {
+    --i; // pre-decrement
+    assert((*i).first == j);
+    assert((*i).second == 'a' + j - 1);
+  }
+  assert(i == m.begin());
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<char>>();
+  test<std::deque<int>, std::vector<char>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<char>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<char, min_allocator<char>>>();
+
+  {
+    // N3644 testing
+    using C = std::flat_map<int, char>;
+    C::iterator ii1{}, ii2{};
+    C::iterator ii4 = ii1;
+    C::const_iterator cii{};
+    assert(ii1 == ii2);
+    assert(ii1 == ii4);
+    assert(!(ii1 != ii2));
+
+    assert((ii1 == cii));
+    assert((cii == ii1));
+    assert(!(ii1 != cii));
+    assert(!(cii != ii1));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.iterators/iterator_comparison.pass.cpp

@@ -0,0 +1,155 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// flat_map iterators should be C++20 random access iterators
+
+#include <compare>
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using KI    = typename KeyContainer::iterator;
+  using I     = M::iterator;
+  using CI    = M::const_iterator;
+  using RI    = M::reverse_iterator;
+  using CRI   = M::const_reverse_iterator;
+
+  static_assert(std::equality_comparable<I>);
+  static_assert(std::equality_comparable<CI>);
+  static_assert(std::equality_comparable<RI>);
+  static_assert(std::equality_comparable<CRI>);
+
+  static_assert(std::totally_ordered<I>);
+  static_assert(std::totally_ordered<CI>);
+  static_assert(std::totally_ordered<RI>);
+  static_assert(std::totally_ordered<CRI>);
+
+  M m = {{1, 'a'}, {2, 'b'}, {3, 'c'}, {4, 'd'}};
+
+  I i1 = m.begin();
+  I i2 = m.begin() + 1;
+
+  assert(i1 == i1);
+  assert(!(i1 != i1));
+  assert(i1 != i2);
+  assert(!(i1 == i2));
+  assert(i1 < i2);
+  assert(!(i1 < i1));
+  assert(i1 <= i1);
+  assert(i1 <= i2);
+  assert(!(i2 <= i1));
+  assert(i2 > i1);
+  assert(!(i2 > i2));
+  assert(i2 >= i1);
+  assert(i2 >= i2);
+  assert(!(i1 >= i2));
+
+  CI ci1 = m.cbegin();
+  CI ci2 = m.cbegin() + 1;
+  assert(ci1 == ci1);
+  assert(!(ci1 != ci1));
+  assert(ci1 != ci2);
+  assert(!(ci1 == ci2));
+  assert(ci1 < ci2);
+  assert(!(ci1 < ci1));
+  assert(ci1 <= ci1);
+  assert(ci1 <= ci2);
+  assert(!(ci2 <= ci1));
+  assert(ci2 > ci1);
+  assert(!(ci2 > ci2));
+  assert(ci2 >= ci1);
+  assert(ci2 >= ci2);
+  assert(!(ci1 >= ci2));
+
+  RI ri1 = m.rbegin();
+  RI ri2 = m.rbegin() + 1;
+  assert(ri1 == ri1);
+  assert(!(ri1 != ri1));
+  assert(ri1 != ri2);
+  assert(!(ri1 == ri2));
+  assert(ri1 < ri2);
+  assert(!(ri1 < ri1));
+  assert(ri1 <= ri1);
+  assert(ri1 <= ri2);
+  assert(!(ri2 <= ri1));
+  assert(ri2 > ri1);
+  assert(!(ri2 > ri2));
+  assert(ri2 >= ri1);
+  assert(ri2 >= ri2);
+  assert(!(ri1 >= ri2));
+
+  CRI cri1 = m.crbegin();
+  CRI cri2 = m.crbegin() + 1;
+  assert(cri1 == cri1);
+  assert(!(cri1 != cri1));
+  assert(cri1 != cri2);
+  assert(!(cri1 == cri2));
+  assert(cri1 < cri2);
+  assert(!(cri1 < cri1));
+  assert(cri1 <= cri1);
+  assert(cri1 <= cri2);
+  assert(!(cri2 <= cri1));
+  assert(cri2 > cri1);
+  assert(!(cri2 > cri2));
+  assert(cri2 >= cri1);
+  assert(cri2 >= cri2);
+  assert(!(cri1 >= cri2));
+
+  if constexpr (std::three_way_comparable<KI>) {
+    static_assert(std::three_way_comparable<I>); // ...of course the wrapped iterators still support <=>.
+    static_assert(std::three_way_comparable<CI>);
+    static_assert(std::three_way_comparable<RI>);
+    static_assert(std::three_way_comparable<CRI>);
+    static_assert(std::same_as<decltype(I() <=> I()), std::strong_ordering>);
+    static_assert(std::same_as<decltype(I() <=> CI()), std::strong_ordering>);
+    static_assert(std::same_as<decltype(CI() <=> CI()), std::strong_ordering>);
+    static_assert(std::same_as<decltype(RI() <=> RI()), std::strong_ordering>);
+    static_assert(std::same_as<decltype(RI() <=> CRI()), std::strong_ordering>);
+    static_assert(std::same_as<decltype(CRI() <=> CRI()), std::strong_ordering>);
+
+    assert(i1 <=> i1 == std::strong_ordering::equivalent);
+    assert(i1 <=> i2 == std::strong_ordering::less);
+    assert(i2 <=> i1 == std::strong_ordering::greater);
+
+    assert(ci1 <=> ci1 == std::strong_ordering::equivalent);
+    assert(ci1 <=> ci2 == std::strong_ordering::less);
+    assert(ci2 <=> ci1 == std::strong_ordering::greater);
+
+    assert(ri1 <=> ri1 == std::strong_ordering::equivalent);
+    assert(ri1 <=> ri2 == std::strong_ordering::less);
+    assert(ri2 <=> ri1 == std::strong_ordering::greater);
+
+    assert(cri1 <=> cri1 == std::strong_ordering::equivalent);
+    assert(cri1 <=> cri2 == std::strong_ordering::less);
+    assert(cri2 <=> cri1 == std::strong_ordering::greater);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<char>>();
+  test<std::deque<int>, std::vector<char>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<char>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<char, min_allocator<char>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.iterators/iterator_concept_conformance.compile.pass.cpp

@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// iterator, const_iterator, reverse_iterator, const_reverse_iterator
+
+#include <flat_map>
+#include <deque>
+#include <functional>
+#include <iterator>
+#include <string>
+#include <vector>
+#include <type_traits>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using C     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using I     = C::iterator;
+  using CI    = C::const_iterator;
+  using RI    = C::reverse_iterator;
+  using CRI   = C::const_reverse_iterator;
+  static_assert(std::random_access_iterator<I>);
+  static_assert(std::random_access_iterator<CI>);
+  static_assert(std::random_access_iterator<RI>);
+  static_assert(std::random_access_iterator<CRI>);
+  static_assert(!std::contiguous_iterator<I>);
+  static_assert(!std::contiguous_iterator<CI>);
+  static_assert(!std::contiguous_iterator<RI>);
+  static_assert(!std::contiguous_iterator<CRI>);
+  static_assert(!std::indirectly_writable<I, std::pair<int, char>>);
+  static_assert(!std::indirectly_writable<CI, std::pair<int, char>>);
+  static_assert(!std::indirectly_writable<RI, std::pair<int, char>>);
+  static_assert(!std::indirectly_writable<CRI, std::pair<int, char>>);
+  static_assert(std::sentinel_for<I, I>);
+  static_assert(std::sentinel_for<I, CI>);
+  static_assert(!std::sentinel_for<I, RI>);
+  static_assert(!std::sentinel_for<I, CRI>);
+  static_assert(std::sentinel_for<CI, I>);
+  static_assert(std::sentinel_for<CI, CI>);
+  static_assert(!std::sentinel_for<CI, RI>);
+  static_assert(!std::sentinel_for<CI, CRI>);
+  static_assert(!std::sentinel_for<RI, I>);
+  static_assert(!std::sentinel_for<RI, CI>);
+  static_assert(std::sentinel_for<RI, RI>);
+  static_assert(std::sentinel_for<RI, CRI>);
+  static_assert(!std::sentinel_for<CRI, I>);
+  static_assert(!std::sentinel_for<CRI, CI>);
+  static_assert(std::sentinel_for<CRI, RI>);
+  static_assert(std::sentinel_for<CRI, CRI>);
+  static_assert(std::indirectly_movable_storable<I, std::pair<int, char>*>);
+  static_assert(std::indirectly_movable_storable<CI, std::pair<int, char>*>);
+  static_assert(std::indirectly_movable_storable<RI, std::pair<int, char>*>);
+  static_assert(std::indirectly_movable_storable<CRI, std::pair<int, char>*>);
+
+#ifdef _LIBCPP_VERSION
+  static_assert(std::is_same_v<typename std::iterator_traits<I>::iterator_category, std::random_access_iterator_tag>);
+  static_assert(std::is_same_v<typename std::iterator_traits<CI>::iterator_category, std::random_access_iterator_tag>);
+  static_assert(std::is_same_v<typename std::iterator_traits<RI>::iterator_category, std::random_access_iterator_tag>);
+  static_assert(std::is_same_v<typename std::iterator_traits<CRI>::iterator_category, std::random_access_iterator_tag>);
+#endif
+}
+
+void test() {
+  test<std::vector<int>, std::vector<char>>();
+  test<std::deque<int>, std::vector<char>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<char>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<char, min_allocator<char>>>();
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.iterators/range_concept_conformance.compile.pass.cpp

@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <ranges>
+#include <string>
+#include <vector>
+#include "MinSequenceContainer.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  {
+    using Key   = typename KeyContainer::value_type;
+    using Value = typename ValueContainer::value_type;
+    using C     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+    static_assert(std::same_as<std::ranges::iterator_t<C>, typename C::iterator>);
+    static_assert(std::ranges::random_access_range<C>);
+    static_assert(!std::ranges::contiguous_range<C>);
+    static_assert(std::ranges::common_range<C>);
+    static_assert(std::ranges::input_range<C>);
+    static_assert(!std::ranges::view<C>);
+    static_assert(std::ranges::sized_range<C>);
+    static_assert(!std::ranges::borrowed_range<C>);
+    static_assert(std::ranges::viewable_range<C>);
+
+    static_assert(std::same_as<std::ranges::iterator_t<const C>, typename C::const_iterator>);
+    static_assert(std::ranges::random_access_range<const C>);
+    static_assert(!std::ranges::contiguous_range<const C>);
+    static_assert(std::ranges::common_range<const C>);
+    static_assert(std::ranges::input_range<const C>);
+    static_assert(!std::ranges::view<const C>);
+    static_assert(std::ranges::sized_range<const C>);
+    static_assert(!std::ranges::borrowed_range<const C>);
+    static_assert(!std::ranges::viewable_range<const C>);
+  }
+}
+
+void test() {
+  test<std::vector<int>, std::vector<char>>();
+  test<std::deque<int>, std::vector<char>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<char>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<char, min_allocator<char>>>();
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.iterators/reverse_iterator.pass.cpp

@@ -0,0 +1,90 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+//       reverse_iterator rbegin() noexcept;
+// const_reverse_iterator rbegin() const noexcept;
+//       reverse_iterator rend()   noexcept;
+// const_reverse_iterator rend()   const noexcept;
+//
+// const_reverse_iterator crbegin() const noexcept;
+// const_reverse_iterator crend()   const noexcept;
+
+#include <cassert>
+#include <cstddef>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <string>
+
+#include <iterator>
+
+#include "test_macros.h"
+#include <iostream>
+
+int main(int, char**) {
+  {
+    using M     = std::flat_map<int, char, std::less<int>, std::deque<int>, std::deque<char>>;
+    M m         = {{1, 'a'}, {2, 'b'}, {3, 'c'}, {4, 'd'}};
+    const M& cm = m;
+    ASSERT_SAME_TYPE(decltype(m.rbegin()), M::reverse_iterator);
+    ASSERT_SAME_TYPE(decltype(m.crbegin()), M::const_reverse_iterator);
+    ASSERT_SAME_TYPE(decltype(cm.rbegin()), M::const_reverse_iterator);
+    ASSERT_SAME_TYPE(decltype(m.rend()), M::reverse_iterator);
+    ASSERT_SAME_TYPE(decltype(m.crend()), M::const_reverse_iterator);
+    ASSERT_SAME_TYPE(decltype(cm.rend()), M::const_reverse_iterator);
+    static_assert(noexcept(m.rbegin()));
+    static_assert(noexcept(cm.rbegin()));
+    static_assert(noexcept(m.crbegin()));
+    static_assert(noexcept(m.rend()));
+    static_assert(noexcept(cm.rend()));
+    static_assert(noexcept(m.crend()));
+    assert(m.size() == 4);
+    assert(std::distance(m.rbegin(), m.rend()) == 4);
+    assert(std::distance(cm.rbegin(), cm.rend()) == 4);
+    assert(std::distance(m.crbegin(), m.crend()) == 4);
+    assert(std::distance(cm.crbegin(), cm.crend()) == 4);
+    M::reverse_iterator i; // default-construct
+    ASSERT_SAME_TYPE(decltype(i->first), const int&);
+    ASSERT_SAME_TYPE(decltype(i->second), char&);
+    i                           = m.rbegin(); // move-assignment
+    M::const_reverse_iterator k = i;          // converting constructor
+    assert(i == k);                           // comparison
+    for (int j = 4; j >= 1; --j, ++i) {       // pre-increment
+      assert(i->first == j);                  // operator->
+      assert(i->second == 'a' + j - 1);
+    }
+    assert(i == m.rend());
+    for (int j = 1; j <= 4; ++j) {
+      --i; // pre-decrement
+      assert((*i).first == j);
+      assert((*i).second == 'a' + j - 1);
+    }
+    assert(i == m.rbegin());
+  }
+  {
+    // N3644 testing
+    using C = std::flat_map<int, char>;
+    C::reverse_iterator ii1{}, ii2{};
+    C::reverse_iterator ii4 = ii1;
+    C::const_reverse_iterator cii{};
+    assert(ii1 == ii2);
+    assert(ii1 == ii4);
+    assert(!(ii1 != ii2));
+
+    assert((ii1 == cii));
+    assert((cii == ii1));
+    assert(!(ii1 != cii));
+    assert(!(cii != ii1));
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/clear.pass.cpp

@@ -0,0 +1,64 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// class flat_map
+
+// void clear() noexcept;
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+// test noexcept
+
+template <class T>
+concept NoExceptClear = requires(T t) {
+  { t.clear() } noexcept;
+};
+
+static_assert(NoExceptClear<std::flat_map<int, int>>);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+static_assert(
+    NoExceptClear<std::flat_map<int, int, std::less<int>, ThrowOnMoveContainer<int>, ThrowOnMoveContainer<int>>>);
+#endif
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  M m = {{1, 2}, {2, 1}, {3, 3}, {4, 1}, {5, 0}};
+  assert(m.size() == 5);
+  ASSERT_NOEXCEPT(m.clear());
+  ASSERT_SAME_TYPE(decltype(m.clear()), void);
+  m.clear();
+  assert(m.size() == 0);
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<int>>();
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/emplace.pass.cpp

@@ -0,0 +1,103 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template <class... Args>
+//   pair<iterator, bool> emplace(Args&&... args);
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+#include <tuple>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "../../../Emplaceable.h"
+#include "DefaultOnly.h"
+#include "min_allocator.h"
+
+// Constraints: is_constructible_v<pair<key_type, mapped_type>, Args...> is true.
+template <class M, class... Args>
+concept CanEmplace = requires(M m, Args&&... args) { m.emplace(std::forward<Args>(args)...); };
+
+using Map = std::flat_map<Emplaceable, Emplaceable>;
+static_assert(CanEmplace<Map>);
+static_assert(CanEmplace<Map, Emplaceable, Emplaceable>);
+static_assert(CanEmplace<Map, std::piecewise_construct_t, std::tuple<int, double>, std::tuple<int, double>>);
+static_assert(!CanEmplace<Map, Emplaceable>);
+static_assert(!CanEmplace<Map, int, double>);
+
+template <class KeyContainer, class ValueContainer>
+void test_simple() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using R     = std::pair<typename M::iterator, bool>;
+  M m;
+  ASSERT_SAME_TYPE(decltype(m.emplace()), R);
+  R r = m.emplace(typename M::value_type(2, 3.5));
+  assert(r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 1);
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == 3.5);
+}
+
+template <class KeyContainer, class ValueContainer>
+void test_emplaceable() {
+  using M = std::flat_map<int, Emplaceable, std::less<int>, KeyContainer, ValueContainer>;
+  using R = std::pair<typename M::iterator, bool>;
+
+  M m;
+  ASSERT_SAME_TYPE(decltype(m.emplace()), R);
+  R r = m.emplace(std::piecewise_construct, std::forward_as_tuple(2), std::forward_as_tuple());
+  assert(r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 1);
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == Emplaceable());
+  r = m.emplace(std::piecewise_construct, std::forward_as_tuple(1), std::forward_as_tuple(2, 3.5));
+  assert(r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 2);
+  assert(m.begin()->first == 1);
+  assert(m.begin()->second == Emplaceable(2, 3.5));
+  r = m.emplace(std::piecewise_construct, std::forward_as_tuple(1), std::forward_as_tuple(2, 3.5));
+  assert(!r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 2);
+  assert(m.begin()->first == 1);
+  assert(m.begin()->second == Emplaceable(2, 3.5));
+}
+
+int main(int, char**) {
+  test_simple<std::vector<int>, std::vector<double>>();
+  test_simple<std::deque<int>, std::vector<double>>();
+  test_simple<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test_simple<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  test_emplaceable<std::vector<int>, std::vector<Emplaceable>>();
+  test_emplaceable<std::deque<int>, std::vector<Emplaceable>>();
+  test_emplaceable<MinSequenceContainer<int>, MinSequenceContainer<Emplaceable>>();
+  test_emplaceable<std::vector<int, min_allocator<int>>, std::vector<Emplaceable, min_allocator<Emplaceable>>>();
+
+  {
+    auto emplace_func = [](auto& m, auto key_arg, auto value_arg) {
+      m.emplace(std::piecewise_construct, std::tuple(key_arg), std::tuple(value_arg));
+    };
+    test_emplace_exception_guarantee(emplace_func);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/emplace_hint.pass.cpp

@@ -0,0 +1,102 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template <class... Args>
+//   iterator emplace_hint(const_iterator position, Args&&... args);
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "../../../Emplaceable.h"
+#include "DefaultOnly.h"
+#include "min_allocator.h"
+#include "../helpers.h"
+
+#if defined(_LIBCPP_VERSION)
+// spec only specifies `emplace(Args&&...)` is_constructible_v<pair<key_type, mapped_type>, Args...> is true.
+// nothing mentioned for emplace_hint
+template <class M, class... Args>
+concept CanEmplaceHint =
+    requires(M m, typename M::const_iterator i, Args&&... args) { m.emplace_hint(i, std::forward<Args>(args)...); };
+
+using Map = std::flat_map<Emplaceable, Emplaceable>;
+static_assert(CanEmplaceHint<Map>);
+static_assert(CanEmplaceHint<Map, Emplaceable, Emplaceable>);
+static_assert(CanEmplaceHint<Map, std::piecewise_construct_t, std::tuple<int, double>, std::tuple<int, double>>);
+static_assert(!CanEmplaceHint<Map, Emplaceable>);
+static_assert(!CanEmplaceHint<Map, int, double>);
+#endif
+
+template <class KeyContainer, class ValueContainer>
+void test_simple() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using R     = M::iterator;
+  M m;
+  ASSERT_SAME_TYPE(decltype(m.emplace_hint(m.cbegin())), R);
+  R r = m.emplace_hint(m.end(), typename M::value_type(2, 3.5));
+  assert(r == m.begin());
+  assert(m.size() == 1);
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == 3.5);
+}
+
+template <class KeyContainer, class ValueContainer>
+void test_emplaceable() {
+  using M = std::flat_map<int, Emplaceable, std::less<int>, KeyContainer, ValueContainer>;
+  using R = M::iterator;
+
+  M m;
+  ASSERT_SAME_TYPE(decltype(m.emplace_hint(m.cbegin())), R);
+  R r = m.emplace_hint(m.end(), std::piecewise_construct, std::forward_as_tuple(2), std::forward_as_tuple());
+  assert(r == m.begin());
+  assert(m.size() == 1);
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == Emplaceable());
+  r = m.emplace_hint(m.end(), std::piecewise_construct, std::forward_as_tuple(1), std::forward_as_tuple(2, 3.5));
+  assert(r == m.begin());
+  assert(m.size() == 2);
+  assert(m.begin()->first == 1);
+  assert(m.begin()->second == Emplaceable(2, 3.5));
+  r = m.emplace_hint(m.end(), std::piecewise_construct, std::forward_as_tuple(1), std::forward_as_tuple(2, 3.5));
+  assert(r == m.begin());
+  assert(m.size() == 2);
+  assert(m.begin()->first == 1);
+  assert(m.begin()->second == Emplaceable(2, 3.5));
+}
+
+int main(int, char**) {
+  test_simple<std::vector<int>, std::vector<double>>();
+  test_simple<std::deque<int>, std::vector<double>>();
+  test_simple<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test_simple<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  test_emplaceable<std::vector<int>, std::vector<Emplaceable>>();
+  test_emplaceable<std::deque<int>, std::vector<Emplaceable>>();
+  test_emplaceable<MinSequenceContainer<int>, MinSequenceContainer<Emplaceable>>();
+  test_emplaceable<std::vector<int, min_allocator<int>>, std::vector<Emplaceable, min_allocator<Emplaceable>>>();
+
+  {
+    auto emplace_func = [](auto& m, auto key_arg, auto value_arg) {
+      m.emplace_hint(m.begin(), std::piecewise_construct, std::tuple(key_arg), std::tuple(value_arg));
+    };
+    test_emplace_exception_guarantee(emplace_func);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/erase_iter.pass.cpp

@@ -0,0 +1,151 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// iterator erase(iterator position);
+// iterator erase(const_iterator position);
+
+#include <compare>
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using P     = std::pair<Key, Value>;
+  using I     = M::iterator;
+
+  P ar[] = {
+      P(1, 1.5),
+      P(2, 2.5),
+      P(3, 3.5),
+      P(4, 4.5),
+      P(5, 5.5),
+      P(6, 6.5),
+      P(7, 7.5),
+      P(8, 8.5),
+  };
+  M m(ar, ar + sizeof(ar) / sizeof(ar[0]));
+  assert(m.size() == 8);
+  std::same_as<I> decltype(auto) i1 = m.erase(std::next(m.cbegin(), 3));
+  assert(m.size() == 7);
+  assert(i1 == std::next(m.begin(), 3));
+  assert(m.begin()->first == 1);
+  assert(m.begin()->second == 1.5);
+  assert(std::next(m.begin())->first == 2);
+  assert(std::next(m.begin())->second == 2.5);
+  assert(std::next(m.begin(), 2)->first == 3);
+  assert(std::next(m.begin(), 2)->second == 3.5);
+  assert(std::next(m.begin(), 3)->first == 5);
+  assert(std::next(m.begin(), 3)->second == 5.5);
+  assert(std::next(m.begin(), 4)->first == 6);
+  assert(std::next(m.begin(), 4)->second == 6.5);
+  assert(std::next(m.begin(), 5)->first == 7);
+  assert(std::next(m.begin(), 5)->second == 7.5);
+  assert(std::next(m.begin(), 6)->first == 8);
+  assert(std::next(m.begin(), 6)->second == 8.5);
+
+  std::same_as<I> decltype(auto) i2 = m.erase(std::next(m.begin(), 0));
+  assert(m.size() == 6);
+  assert(i2 == m.begin());
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == 2.5);
+  assert(std::next(m.begin())->first == 3);
+  assert(std::next(m.begin())->second == 3.5);
+  assert(std::next(m.begin(), 2)->first == 5);
+  assert(std::next(m.begin(), 2)->second == 5.5);
+  assert(std::next(m.begin(), 3)->first == 6);
+  assert(std::next(m.begin(), 3)->second == 6.5);
+  assert(std::next(m.begin(), 4)->first == 7);
+  assert(std::next(m.begin(), 4)->second == 7.5);
+  assert(std::next(m.begin(), 5)->first == 8);
+  assert(std::next(m.begin(), 5)->second == 8.5);
+
+  std::same_as<I> decltype(auto) i3 = m.erase(std::next(m.cbegin(), 5));
+  assert(m.size() == 5);
+  assert(i3 == m.end());
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == 2.5);
+  assert(std::next(m.begin())->first == 3);
+  assert(std::next(m.begin())->second == 3.5);
+  assert(std::next(m.begin(), 2)->first == 5);
+  assert(std::next(m.begin(), 2)->second == 5.5);
+  assert(std::next(m.begin(), 3)->first == 6);
+  assert(std::next(m.begin(), 3)->second == 6.5);
+  assert(std::next(m.begin(), 4)->first == 7);
+  assert(std::next(m.begin(), 4)->second == 7.5);
+
+  std::same_as<I> decltype(auto) i4 = m.erase(std::next(m.begin(), 1));
+  assert(m.size() == 4);
+  assert(i4 == std::next(m.begin()));
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == 2.5);
+  assert(std::next(m.begin())->first == 5);
+  assert(std::next(m.begin())->second == 5.5);
+  assert(std::next(m.begin(), 2)->first == 6);
+  assert(std::next(m.begin(), 2)->second == 6.5);
+  assert(std::next(m.begin(), 3)->first == 7);
+  assert(std::next(m.begin(), 3)->second == 7.5);
+
+  std::same_as<I> decltype(auto) i5 = m.erase(std::next(m.cbegin(), 2));
+  assert(m.size() == 3);
+  assert(i5 == std::next(m.begin(), 2));
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == 2.5);
+  assert(std::next(m.begin())->first == 5);
+  assert(std::next(m.begin())->second == 5.5);
+  assert(std::next(m.begin(), 2)->first == 7);
+  assert(std::next(m.begin(), 2)->second == 7.5);
+
+  std::same_as<I> decltype(auto) i6 = m.erase(std::next(m.begin(), 2));
+  assert(m.size() == 2);
+  assert(i6 == std::next(m.begin(), 2));
+  assert(m.begin()->first == 2);
+  assert(m.begin()->second == 2.5);
+  assert(std::next(m.begin())->first == 5);
+  assert(std::next(m.begin())->second == 5.5);
+
+  std::same_as<I> decltype(auto) i7 = m.erase(std::next(m.cbegin(), 0));
+  assert(m.size() == 1);
+  assert(i7 == std::next(m.begin(), 0));
+  assert(m.begin()->first == 5);
+  assert(m.begin()->second == 5.5);
+
+  std::same_as<I> decltype(auto) i8 = m.erase(m.begin());
+  assert(m.size() == 0);
+  assert(i8 == m.begin());
+  assert(i8 == m.end());
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto erase_function = [](auto& m, auto) { m.erase(m.begin() + 2); };
+    test_erase_exception_guarantee(erase_function);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/erase_iter_iter.pass.cpp

@@ -0,0 +1,109 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// iterator erase(const_iterator first, const_iterator last);
+
+#include <compare>
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using P     = std::pair<Key, Value>;
+  using I     = M::iterator;
+
+  P ar[] = {
+      P(1, 1.5),
+      P(2, 2.5),
+      P(3, 3.5),
+      P(4, 4.5),
+      P(5, 5.5),
+      P(6, 6.5),
+      P(7, 7.5),
+      P(8, 8.5),
+  };
+  M m(ar, ar + sizeof(ar) / sizeof(ar[0]));
+  assert(m.size() == 8);
+  std::same_as<I> decltype(auto) i1 = m.erase(m.cbegin(), m.cbegin());
+  assert(m.size() == 8);
+  assert(i1 == m.begin());
+  assert(m.begin()->first == 1);
+  assert(m.begin()->second == 1.5);
+  assert(std::next(m.begin())->first == 2);
+  assert(std::next(m.begin())->second == 2.5);
+  assert(std::next(m.begin(), 2)->first == 3);
+  assert(std::next(m.begin(), 2)->second == 3.5);
+  assert(std::next(m.begin(), 3)->first == 4);
+  assert(std::next(m.begin(), 3)->second == 4.5);
+  assert(std::next(m.begin(), 4)->first == 5);
+  assert(std::next(m.begin(), 4)->second == 5.5);
+  assert(std::next(m.begin(), 5)->first == 6);
+  assert(std::next(m.begin(), 5)->second == 6.5);
+  assert(std::next(m.begin(), 6)->first == 7);
+  assert(std::next(m.begin(), 6)->second == 7.5);
+  assert(std::next(m.begin(), 7)->first == 8);
+  assert(std::next(m.begin(), 7)->second == 8.5);
+
+  std::same_as<I> decltype(auto) i2 = m.erase(m.cbegin(), std::next(m.cbegin(), 2));
+  assert(m.size() == 6);
+  assert(i2 == m.begin());
+  assert(std::next(m.begin(), 0)->first == 3);
+  assert(std::next(m.begin(), 0)->second == 3.5);
+  assert(std::next(m.begin(), 1)->first == 4);
+  assert(std::next(m.begin(), 1)->second == 4.5);
+  assert(std::next(m.begin(), 2)->first == 5);
+  assert(std::next(m.begin(), 2)->second == 5.5);
+  assert(std::next(m.begin(), 3)->first == 6);
+  assert(std::next(m.begin(), 3)->second == 6.5);
+  assert(std::next(m.begin(), 4)->first == 7);
+  assert(std::next(m.begin(), 4)->second == 7.5);
+  assert(std::next(m.begin(), 5)->first == 8);
+  assert(std::next(m.begin(), 5)->second == 8.5);
+
+  std::same_as<I> decltype(auto) i3 = m.erase(std::next(m.cbegin(), 2), std::next(m.cbegin(), 6));
+  assert(m.size() == 2);
+  assert(i3 == std::next(m.begin(), 2));
+  assert(std::next(m.begin(), 0)->first == 3);
+  assert(std::next(m.begin(), 0)->second == 3.5);
+  assert(std::next(m.begin(), 1)->first == 4);
+  assert(std::next(m.begin(), 1)->second == 4.5);
+
+  std::same_as<I> decltype(auto) i4 = m.erase(m.cbegin(), m.cend());
+  assert(m.size() == 0);
+  assert(i4 == m.begin());
+  assert(i4 == m.end());
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto erase_function = [](auto& m, auto) { m.erase(m.begin(), m.begin() + 2); };
+    test_erase_exception_guarantee(erase_function);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/erase_key.pass.cpp

@@ -0,0 +1,91 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// size_type erase(const key_type& k);
+
+#include <compare>
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer, class Compare = std::less<>>
+void test() {
+  using M = std::flat_map<int, char, Compare, KeyContainer, ValueContainer>;
+
+  auto make = [](std::initializer_list<int> il) {
+    M m;
+    for (int i : il) {
+      m.emplace(i, i);
+    }
+    return m;
+  };
+  M m = make({1, 2, 3, 4, 5, 6, 7, 8});
+  ASSERT_SAME_TYPE(decltype(m.erase(9)), typename M::size_type);
+  auto n = m.erase(9);
+  assert(n == 0);
+  assert(m == make({1, 2, 3, 4, 5, 6, 7, 8}));
+  n = m.erase(4);
+  assert(n == 1);
+  assert(m == make({1, 2, 3, 5, 6, 7, 8}));
+  n = m.erase(1);
+  assert(n == 1);
+  assert(m == make({2, 3, 5, 6, 7, 8}));
+  n = m.erase(8);
+  assert(n == 1);
+  assert(m == make({2, 3, 5, 6, 7}));
+  n = m.erase(3);
+  assert(n == 1);
+  assert(m == make({2, 5, 6, 7}));
+  n = m.erase(4);
+  assert(n == 0);
+  assert(m == make({2, 5, 6, 7}));
+  n = m.erase(6);
+  assert(n == 1);
+  assert(m == make({2, 5, 7}));
+  n = m.erase(7);
+  assert(n == 1);
+  assert(m == make({2, 5}));
+  n = m.erase(2);
+  assert(n == 1);
+  assert(m == make({5}));
+  n = m.erase(5);
+  assert(n == 1);
+  assert(m.empty());
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<char>>();
+  test<std::vector<int>, std::vector<char>, std::greater<>>();
+  test<std::deque<int>, std::vector<char>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<char>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<char, min_allocator<char>>>();
+
+  {
+    auto erase_function = [](auto& m, auto key_arg) {
+      using Map = std::decay_t<decltype(m)>;
+      using Key = typename Map::key_type;
+      const Key key{key_arg};
+      m.erase(key);
+    };
+    test_erase_exception_guarantee(erase_function);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/erase_key_transparent.pass.cpp

@@ -0,0 +1,144 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// size_type erase(K&& k);
+
+#include <compare>
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+// Constraints: The qualified-id Compare::is_transparent is valid and denotes a type.
+template <class M>
+concept CanErase        = requires(M m, Transparent<int> k) { m.erase(k); };
+using TransparentMap    = std::flat_map<int, double, TransparentComparator>;
+using NonTransparentMap = std::flat_map<int, double, NonTransparentComparator>;
+static_assert(CanErase<TransparentMap>);
+static_assert(!CanErase<const TransparentMap>);
+static_assert(!CanErase<NonTransparentMap>);
+static_assert(!CanErase<const NonTransparentMap>);
+
+template <class Key, class It>
+struct HeterogeneousKey {
+  explicit HeterogeneousKey(Key key, It it) : key_(key), it_(it) {}
+  operator It() && { return it_; }
+  auto operator<=>(Key key) const { return key_ <=> key; }
+  friend bool operator<(const HeterogeneousKey&, const HeterogeneousKey&) {
+    assert(false);
+    return false;
+  }
+  Key key_;
+  It it_;
+};
+
+template <class KeyContainer, class ValueContainer>
+void test_simple() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  M m = {{1, 1}, {2, 2}, {3, 3}, {4, 4}};
+  ASSERT_SAME_TYPE(decltype(m.erase(9)), typename M::size_type);
+  auto n = m.erase(3); // erase(K&&) [with K=int]
+  assert(n == 1);
+  assert((m == M{{1, 1}, {2, 2}, {4, 4}}));
+  typename M::key_type lvalue = 2;
+  n                           = m.erase(lvalue); // erase(K&&) [with K=int&]
+  assert(n == 1);
+  assert((m == M{{1, 1}, {4, 4}}));
+  const typename M::key_type const_lvalue = 1;
+  n                                       = m.erase(const_lvalue); // erase(const key_type&)
+  assert(n == 1);
+  assert((m == M{{4, 4}}));
+}
+
+template <class KeyContainer, class ValueContainer>
+void test_transparent_comparator() {
+  using M = std::flat_map<std::string, int, TransparentComparator, KeyContainer, ValueContainer>;
+  M m     = {{"alpha", 1}, {"beta", 2}, {"epsilon", 3}, {"eta", 4}, {"gamma", 5}};
+  ASSERT_SAME_TYPE(decltype(m.erase(Transparent<std::string>{"abc"})), typename M::size_type);
+
+  auto n = m.erase(Transparent<std::string>{"epsilon"});
+  assert(n == 1);
+
+  M expected = {{"alpha", 1}, {"beta", 2}, {"eta", 4}, {"gamma", 5}};
+  assert(m == expected);
+
+  auto n2 = m.erase(Transparent<std::string>{"aaa"});
+  assert(n2 == 0);
+  assert(m == expected);
+}
+
+int main(int, char**) {
+  test_simple<std::vector<int>, std::vector<double>>();
+  test_simple<std::deque<int>, std::vector<double>>();
+  test_simple<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test_simple<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  test_transparent_comparator<std::vector<std::string>, std::vector<int>>();
+  test_transparent_comparator<std::deque<std::string>, std::vector<int>>();
+  test_transparent_comparator<MinSequenceContainer<std::string>, MinSequenceContainer<int>>();
+  test_transparent_comparator<std::vector<std::string, min_allocator<std::string>>,
+                              std::vector<int, min_allocator<int>>>();
+
+  {
+    // P2077's HeterogeneousKey example
+    using M                           = std::flat_map<int, int, std::less<>>;
+    M m                               = {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}, {8, 8}};
+    auto h1                           = HeterogeneousKey<int, M::iterator>(8, m.begin());
+    std::same_as<M::size_type> auto n = m.erase(h1); // lvalue is not convertible to It; erase(K&&) is the best match
+    assert(n == 1);
+    assert((m == M{{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}}));
+    std::same_as<M::iterator> auto it = m.erase(std::move(h1)); // rvalue is convertible to It; erase(K&&) drops out
+    assert(it == m.begin());
+    assert((m == M{{2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}}));
+  }
+  {
+    using M                           = std::flat_map<int, int, std::less<>>;
+    M m                               = {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}, {8, 8}};
+    auto h1                           = HeterogeneousKey<int, M::const_iterator>(8, m.begin());
+    std::same_as<M::size_type> auto n = m.erase(h1); // lvalue is not convertible to It; erase(K&&) is the best match
+    assert(n == 1);
+    assert((m == M{{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}}));
+    std::same_as<M::iterator> auto it = m.erase(std::move(h1)); // rvalue is convertible to It; erase(K&&) drops out
+    assert(it == m.begin());
+    assert((m == M{{2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}}));
+  }
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    auto n = m.erase(Transparent<int>{3});
+    assert(n == 1);
+    assert(transparent_used);
+  }
+  {
+    auto erase_transparent = [](auto& m, auto key_arg) {
+      using Map = std::decay_t<decltype(m)>;
+      using Key = typename Map::key_type;
+      m.erase(Transparent<Key>{key_arg});
+    };
+    test_erase_exception_guarantee(erase_transparent);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/extract.pass.cpp

@@ -0,0 +1,91 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// containers extract() &&;
+
+#include <algorithm>
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class T>
+concept CanExtract = requires(T&& t) { std::forward<T>(t).extract(); };
+
+static_assert(CanExtract<std::flat_map<int, int>&&>);
+static_assert(!CanExtract<std::flat_map<int, int>&>);
+static_assert(!CanExtract<std::flat_map<int, int> const&>);
+static_assert(!CanExtract<std::flat_map<int, int> const&&>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using M = std::flat_map<int, int, std::less<int>, KeyContainer, ValueContainer>;
+  M m     = M({1, 2, 3}, {4, 5, 6});
+
+  std::same_as<typename M::containers> auto containers = std::move(m).extract();
+
+  auto expected_keys   = {1, 2, 3};
+  auto expected_values = {4, 5, 6};
+  assert(std::ranges::equal(containers.keys, expected_keys));
+  assert(std::ranges::equal(containers.values, expected_values));
+  check_invariant(m);
+  LIBCPP_ASSERT(m.empty());
+  LIBCPP_ASSERT(m.keys().size() == 0);
+  LIBCPP_ASSERT(m.values().size() == 0);
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<int>>();
+  test<std::deque<int>, std::vector<int>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<int>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>();
+  {
+    // extracted object maintains invariant if one of underlying container does not clear after move
+    using M = std::flat_map<int, int, std::less<>, std::vector<int>, CopyOnlyVector<int>>;
+    M m     = M({1, 2, 3}, {1, 2, 3});
+    std::same_as<M::containers> auto containers = std::move(m).extract();
+    assert(containers.keys.size() == 3);
+    assert(containers.values.size() == 3);
+    check_invariant(m);
+    LIBCPP_ASSERT(m.empty());
+    LIBCPP_ASSERT(m.keys().size() == 0);
+    LIBCPP_ASSERT(m.values().size() == 0);
+  }
+
+  {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    using KeyContainer   = std::vector<int>;
+    using ValueContainer = ThrowOnMoveContainer<int>;
+    using M              = std::flat_map<int, int, std::ranges::less, KeyContainer, ValueContainer>;
+
+    M m;
+    m.emplace(1, 1);
+    m.emplace(2, 2);
+    try {
+      auto c = std::move(m).extract();
+      assert(false);
+    } catch (int) {
+      check_invariant(m);
+      // In libc++, we try to erase the key after value emplacement failure.
+      // and after erasure failure, we clear the flat_map
+      LIBCPP_ASSERT(m.size() == 0);
+    }
+#endif
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_cv.pass.cpp

@@ -0,0 +1,83 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// pair<iterator, bool> insert(const value_type& v);
+
+#include <flat_map>
+#include <deque>
+#include <cassert>
+#include <functional>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "../helpers.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using R     = std::pair<typename M::iterator, bool>;
+  using VT    = typename M::value_type;
+  M m;
+
+  const VT v1(2, 2.5);
+  std::same_as<R> decltype(auto) r = m.insert(v1);
+  assert(r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 1);
+  assert(r.first->first == 2);
+  assert(r.first->second == 2.5);
+
+  const VT v2(1, 1.5);
+  r = m.insert(v2);
+  assert(r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 2);
+  assert(r.first->first == 1);
+  assert(r.first->second == 1.5);
+
+  const VT v3(3, 3.5);
+  r = m.insert(v3);
+  assert(r.second);
+  assert(r.first == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r.first->first == 3);
+  assert(r.first->second == 3.5);
+
+  const VT v4(3, 4.5);
+  r = m.insert(v4);
+  assert(!r.second);
+  assert(r.first == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r.first->first == 3);
+  assert(r.first->second == 3.5);
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto insert_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap    = std::decay_t<decltype(m)>;
+      using value_type = typename FlatMap::value_type;
+      const value_type p(std::piecewise_construct, std::tuple(key_arg), std::tuple(value_arg));
+      m.insert(p);
+    };
+    test_emplace_exception_guarantee(insert_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_initializer_list.pass.cpp

@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// void insert(initializer_list<value_type> il);
+
+#include <flat_map>
+#include <cassert>
+#include <functional>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using V     = std::pair<const int, double>;
+
+  M m = {{1, 1}, {1, 1.5}, {1, 2}, {3, 1}, {3, 1.5}, {3, 2}};
+  m.insert({
+      {4, 1},
+      {4, 1.5},
+      {4, 2},
+      {1, 1},
+      {1, 1.5},
+      {1, 2},
+      {2, 1},
+      {2, 1.5},
+      {2, 2},
+  });
+  assert(m.size() == 4);
+  assert(std::distance(m.begin(), m.end()) == 4);
+  assert(*m.begin() == V(1, 1));
+  assert(*std::next(m.begin()) == V(2, 1));
+  assert(*std::next(m.begin(), 2) == V(3, 1));
+  assert(*std::next(m.begin(), 3) == V(4, 1));
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto insert_func = [](auto& m, const auto& newValues) {
+      using FlatMap                        = std::decay_t<decltype(m)>;
+      using value_type                     = typename FlatMap::value_type;
+      std::initializer_list<value_type> il = {{newValues[0].first, newValues[0].second}};
+      m.insert(il);
+    };
+    test_insert_range_exception_guarantee(insert_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_iter_cv.pass.cpp

@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// iterator insert(const_iterator position, const value_type& v);
+
+#include <flat_map>
+#include <cassert>
+#include <functional>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "../helpers.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using R     = typename M::iterator;
+  using VT    = typename M::value_type;
+
+  M m;
+  const VT v1(2, 2.5);
+  std::same_as<R> decltype(auto) r = m.insert(m.end(), v1);
+  assert(r == m.begin());
+  assert(m.size() == 1);
+  assert(r->first == 2);
+  assert(r->second == 2.5);
+
+  const VT v2(1, 1.5);
+  r = m.insert(m.end(), v2);
+  assert(r == m.begin());
+  assert(m.size() == 2);
+  assert(r->first == 1);
+  assert(r->second == 1.5);
+
+  const VT v3(3, 3.5);
+  r = m.insert(m.end(), v3);
+  assert(r == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r->first == 3);
+  assert(r->second == 3.5);
+
+  const VT v4(3, 4.5);
+  r = m.insert(m.end(), v4);
+  assert(r == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r->first == 3);
+  assert(r->second == 3.5);
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto insert_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap    = std::decay_t<decltype(m)>;
+      using value_type = typename FlatMap::value_type;
+      const value_type p(std::piecewise_construct, std::tuple(key_arg), std::tuple(value_arg));
+      m.insert(m.begin(), p);
+    };
+    test_emplace_exception_guarantee(insert_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_iter_iter.pass.cpp

@@ -0,0 +1,89 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template <class InputIterator>
+//   void insert(InputIterator first, InputIterator last);
+
+#include <flat_map>
+#include <cassert>
+#include <functional>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "test_iterators.h"
+#include "min_allocator.h"
+
+// test constraint InputIterator
+template <class M, class... Args>
+concept CanInsert = requires(M m, Args&&... args) { m.insert(std::forward<Args>(args)...); };
+
+using Map  = std::flat_map<int, int>;
+using Pair = std::pair<int, int>;
+
+static_assert(CanInsert<Map, Pair*, Pair*>);
+static_assert(CanInsert<Map, cpp17_input_iterator<Pair*>, cpp17_input_iterator<Pair*>>);
+static_assert(!CanInsert<Map, int, int>);
+static_assert(!CanInsert<Map, cpp20_input_iterator<Pair*>, cpp20_input_iterator<Pair*>>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using P = std::pair<int, double>;
+  using M = std::flat_map<int, double, std::less<int>, KeyContainer, ValueContainer>;
+
+  P ar1[] = {
+      P(2, 1),
+      P(2, 1.5),
+      P(2, 2),
+      P(1, 1),
+      P(1, 1.5),
+      P(1, 2),
+      P(3, 1),
+      P(3, 1.5),
+      P(3, 2),
+  };
+  P ar2[] = {
+      P(4, 1),
+      P(4, 1.5),
+      P(4, 2),
+      P(1, 1),
+      P(1, 1.5),
+      P(1, 2),
+      P(0, 1),
+      P(0, 1.5),
+      P(0, 2),
+  };
+
+  M m;
+  m.insert(cpp17_input_iterator<P*>(ar1), cpp17_input_iterator<P*>(ar1 + sizeof(ar1) / sizeof(ar1[0])));
+  assert(m.size() == 3);
+  M expected{{1, 1}, {2, 1}, {3, 1}};
+  assert(m == expected);
+
+  m.insert(cpp17_input_iterator<P*>(ar2), cpp17_input_iterator<P*>(ar2 + sizeof(ar2) / sizeof(ar2[0])));
+  assert(m.size() == 5);
+  M expected2{{0, 1}, {1, 1}, {2, 1}, {3, 1}, {4, 1}};
+  assert(m == expected2);
+}
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto insert_func = [](auto& m, const auto& newValues) { m.insert(newValues.begin(), newValues.end()); };
+    test_insert_range_exception_guarantee(insert_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_iter_rv.pass.cpp

@@ -0,0 +1,88 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+//     iterator insert(const_iterator position, value_type&&);
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "MoveOnly.h"
+#include "min_allocator.h"
+#include "../helpers.h"
+#include "test_macros.h"
+
+template <class Container, class Pair>
+void do_insert_iter_rv_test() {
+  using M = Container;
+  using P = Pair;
+  using R = typename M::iterator;
+  M m;
+  std::same_as<R> decltype(auto) r = m.insert(m.end(), P(2, 2));
+  assert(r == m.begin());
+  assert(m.size() == 1);
+  assert(r->first == 2);
+  assert(r->second == 2);
+
+  r = m.insert(m.end(), P(1, 1));
+  assert(r == m.begin());
+  assert(m.size() == 2);
+  assert(r->first == 1);
+  assert(r->second == 1);
+
+  r = m.insert(m.end(), P(3, 3));
+  assert(r == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r->first == 3);
+  assert(r->second == 3);
+
+  r = m.insert(m.end(), P(3, 4));
+  assert(r == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r->first == 3);
+  assert(r->second == 3);
+}
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using P     = std::pair<Key, Value>;
+  using CP    = std::pair<const Key, Value>;
+
+  do_insert_iter_rv_test<M, P>();
+  do_insert_iter_rv_test<M, CP>();
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::vector<int>, std::vector<MoveOnly>>();
+  test<std::deque<int>, std::deque<double>>();
+  test<std::deque<int>, std::deque<MoveOnly>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<MoveOnly>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<MoveOnly, min_allocator<MoveOnly>>>();
+
+  {
+    auto insert_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap    = std::decay_t<decltype(m)>;
+      using value_type = typename FlatMap::value_type;
+      value_type p(std::piecewise_construct, std::tuple(key_arg), std::tuple(value_arg));
+      m.insert(m.begin(), std::move(p));
+    };
+    test_emplace_exception_guarantee(insert_func);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_or_assign.pass.cpp

@@ -0,0 +1,326 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "MoveOnly.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+#include "../helpers.h"
+
+// template<class M>
+//   pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
+// template<class M>
+//   pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
+// template<class M>
+//   iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
+// template<class M>
+//   iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
+
+// Constraints: is_assignable_v<mapped_type&, M> is true and is_constructible_v<mapped_type, M> is true.
+template <class Map, class K, class M>
+concept CanInsertOrAssign =
+    requires(Map map, K&& k, M&& m) { map.insert_or_assign(std::forward<K>(k), std::forward<M>(m)); };
+
+template <class Map, class K, class M>
+concept CanInsertOrAssignIter = requires(Map map, typename Map::const_iterator iter, K&& k, M&& m) {
+  map.insert_or_assign(iter, std::forward<K>(k), std::forward<M>(m));
+};
+
+template <class From>
+struct ConstructAndAssignFrom {
+  explicit ConstructAndAssignFrom(From);
+  ConstructAndAssignFrom& operator=(From);
+};
+
+template <class From>
+struct ConstructFrom {
+  explicit ConstructFrom(From);
+};
+
+template <class From>
+struct AssignFrom {
+  AssignFrom& operator=(From);
+};
+
+struct V {};
+
+static_assert(CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>>, const int&, V>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>>, const int&, int>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, ConstructFrom<V>>, const int&, V>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, AssignFrom<V>>, const int&, V>);
+
+static_assert(CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>>, int&&, V>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>>, int&&, int>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, ConstructFrom<V>>, int&&, V>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, AssignFrom<V>>, int&&, V>);
+
+static_assert(CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>>, const int&, V>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>>, const int&, int>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructFrom<V>>, const int&, V>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, AssignFrom<V>>, const int&, V>);
+
+static_assert(CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>>, int&&, V>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>>, int&&, int>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructFrom<V>>, int&&, V>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, AssignFrom<V>>, int&&, V>);
+
+template <class KeyContainer, class ValueContainer>
+void test_cv_key() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, TransparentComparator, KeyContainer, ValueContainer>;
+  { // pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
+    using R = std::pair<typename M::iterator, bool>;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(i, Moveable(i, (double)i));
+    assert(m.size() == 10);
+
+    for (int i = 0; i < 20; i += 2) {
+      Moveable mv(i + 1, i + 1);
+      std::same_as<R> decltype(auto) r1 = m.insert_or_assign(i, std::move(mv));
+      assert(m.size() == 10);
+      assert(!r1.second);                      // was not inserted
+      assert(mv.moved());                      // was moved from
+      assert(r1.first->first == i);            // key
+      assert(r1.first->second.get() == i + 1); // value
+    }
+
+    Moveable mv1(5, 5.0);
+    std::same_as<R> decltype(auto) r2 = m.insert_or_assign(-1, std::move(mv1));
+    assert(m.size() == 11);
+    assert(r2.second);                   // was inserted
+    assert(mv1.moved());                 // was moved from
+    assert(r2.first->first == -1);       // key
+    assert(r2.first->second.get() == 5); // value
+
+    Moveable mv2(9, 9.0);
+    std::same_as<R> decltype(auto) r3 = m.insert_or_assign(3, std::move(mv2));
+    assert(m.size() == 12);
+    assert(r3.second);                   // was inserted
+    assert(mv2.moved());                 // was moved from
+    assert(r3.first->first == 3);        // key
+    assert(r3.first->second.get() == 9); // value
+
+    Moveable mv3(-1, 5.0);
+    std::same_as<R> decltype(auto) r4 = m.insert_or_assign(117, std::move(mv3));
+    assert(m.size() == 13);
+    assert(r4.second);                    // was inserted
+    assert(mv3.moved());                  // was moved from
+    assert(r4.first->first == 117);       // key
+    assert(r4.first->second.get() == -1); // value
+  }
+
+  { // iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
+    M m;
+    using R = M::iterator;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(i, Moveable(i, (double)i));
+    assert(m.size() == 10);
+    typename M::const_iterator it = m.find(2);
+
+    Moveable mv1(3, 3.0);
+    std::same_as<R> decltype(auto) r1 = m.insert_or_assign(it, 2, std::move(mv1));
+    assert(m.size() == 10);
+    assert(mv1.moved());           // was moved from
+    assert(r1->first == 2);        // key
+    assert(r1->second.get() == 3); // value
+
+    Moveable mv2(5, 5.0);
+    std::same_as<R> decltype(auto) r2 = m.insert_or_assign(it, 3, std::move(mv2));
+    assert(m.size() == 11);
+    assert(mv2.moved());           // was moved from
+    assert(r2->first == 3);        // key
+    assert(r2->second.get() == 5); // value
+
+    // wrong hint: begin()
+    Moveable mv3(7, 7.0);
+    std::same_as<R> decltype(auto) r3 = m.insert_or_assign(m.begin(), 4, std::move(mv3));
+    assert(m.size() == 11);
+    assert(mv3.moved());           // was moved from
+    assert(r3->first == 4);        // key
+    assert(r3->second.get() == 7); // value
+
+    Moveable mv4(9, 9.0);
+    std::same_as<R> decltype(auto) r4 = m.insert_or_assign(m.begin(), 5, std::move(mv4));
+    assert(m.size() == 12);
+    assert(mv4.moved());           // was moved from
+    assert(r4->first == 5);        // key
+    assert(r4->second.get() == 9); // value
+
+    // wrong hint: end()
+    Moveable mv5(11, 11.0);
+    std::same_as<R> decltype(auto) r5 = m.insert_or_assign(m.end(), 6, std::move(mv5));
+    assert(m.size() == 12);
+    assert(mv5.moved());            // was moved from
+    assert(r5->first == 6);         // key
+    assert(r5->second.get() == 11); // value
+
+    Moveable mv6(13, 13.0);
+    std::same_as<R> decltype(auto) r6 = m.insert_or_assign(m.end(), 7, std::move(mv6));
+    assert(m.size() == 13);
+    assert(mv6.moved());            // was moved from
+    assert(r6->first == 7);         // key
+    assert(r6->second.get() == 13); // value
+
+    // wrong hint: third element
+    Moveable mv7(15, 15.0);
+    std::same_as<R> decltype(auto) r7 = m.insert_or_assign(std::next(m.begin(), 2), 8, std::move(mv7));
+    assert(m.size() == 13);
+    assert(mv7.moved());            // was moved from
+    assert(r7->first == 8);         // key
+    assert(r7->second.get() == 15); // value
+
+    Moveable mv8(17, 17.0);
+    std::same_as<R> decltype(auto) r8 = m.insert_or_assign(std::next(m.begin(), 2), 9, std::move(mv8));
+    assert(m.size() == 14);
+    assert(mv8.moved());            // was moved from
+    assert(r8->first == 9);         // key
+    assert(r8->second.get() == 17); // value
+  }
+}
+
+template <class KeyContainer, class ValueContainer>
+void test_rv_key() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, TransparentComparator, KeyContainer, ValueContainer>;
+
+  { // pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
+    using R = std::pair<typename M::iterator, bool>;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(Moveable(i, (double)i), Moveable(i + 1, (double)i + 1));
+    assert(m.size() == 10);
+
+    Moveable mvkey1(2, 2.0);
+    Moveable mv1(4, 4.0);
+    std::same_as<R> decltype(auto) r1 = m.insert_or_assign(std::move(mvkey1), std::move(mv1));
+    assert(m.size() == 10);
+    assert(!r1.second);                  // was not inserted
+    assert(!mvkey1.moved());             // was not moved from
+    assert(mv1.moved());                 // was moved from
+    assert(r1.first->first == mvkey1);   // key
+    assert(r1.first->second.get() == 4); // value
+
+    Moveable mvkey2(3, 3.0);
+    Moveable mv2(5, 5.0);
+    std::same_as<R> decltype(auto) r2 = m.try_emplace(std::move(mvkey2), std::move(mv2));
+    assert(m.size() == 11);
+    assert(r2.second);                   // was inserted
+    assert(mv2.moved());                 // was moved from
+    assert(mvkey2.moved());              // was moved from
+    assert(r2.first->first.get() == 3);  // key
+    assert(r2.first->second.get() == 5); // value
+  }
+  { // iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
+    using R = M::iterator;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(Moveable(i, (double)i), Moveable(i + 1, (double)i + 1));
+    assert(m.size() == 10);
+    typename M::const_iterator it = std::next(m.cbegin());
+
+    Moveable mvkey1(2, 2.0);
+    Moveable mv1(4, 4.0);
+    std::same_as<R> decltype(auto) r1 = m.insert_or_assign(it, std::move(mvkey1), std::move(mv1));
+    assert(m.size() == 10);
+    assert(mv1.moved());           // was moved from
+    assert(!mvkey1.moved());       // was not moved from
+    assert(r1->first == mvkey1);   // key
+    assert(r1->second.get() == 4); // value
+
+    Moveable mvkey2(3, 3.0);
+    Moveable mv2(5, 5.0);
+    std::same_as<R> decltype(auto) r2 = m.insert_or_assign(it, std::move(mvkey2), std::move(mv2));
+    assert(m.size() == 11);
+    assert(mv2.moved());           // was moved from
+    assert(mvkey2.moved());        // was moved from
+    assert(r2->first.get() == 3);  // key
+    assert(r2->second.get() == 5); // value
+
+    // wrong hint: begin()
+    Moveable mvkey3(6, 6.0);
+    Moveable mv3(8, 8.0);
+    std::same_as<R> decltype(auto) r3 = m.insert_or_assign(m.begin(), std::move(mvkey3), std::move(mv3));
+    assert(m.size() == 11);
+    assert(mv3.moved());           // was moved from
+    assert(!mvkey3.moved());       // was not moved from
+    assert(r3->first == mvkey3);   // key
+    assert(r3->second.get() == 8); // value
+
+    Moveable mvkey4(7, 7.0);
+    Moveable mv4(9, 9.0);
+    std::same_as<R> decltype(auto) r4 = m.insert_or_assign(m.begin(), std::move(mvkey4), std::move(mv4));
+    assert(m.size() == 12);
+    assert(mv4.moved());           // was moved from
+    assert(mvkey4.moved());        // was moved from
+    assert(r4->first.get() == 7);  // key
+    assert(r4->second.get() == 9); // value
+
+    // wrong hint: end()
+    Moveable mvkey5(8, 8.0);
+    Moveable mv5(10, 10.0);
+    std::same_as<R> decltype(auto) r5 = m.insert_or_assign(m.end(), std::move(mvkey5), std::move(mv5));
+    assert(m.size() == 12);
+    assert(mv5.moved());            // was moved from
+    assert(!mvkey5.moved());        // was not moved from
+    assert(r5->first == mvkey5);    // key
+    assert(r5->second.get() == 10); // value
+
+    Moveable mvkey6(9, 9.0);
+    Moveable mv6(11, 11.0);
+    std::same_as<R> decltype(auto) r6 = m.insert_or_assign(m.end(), std::move(mvkey6), std::move(mv6));
+    assert(m.size() == 13);
+    assert(mv6.moved());            // was moved from
+    assert(mvkey6.moved());         // was moved from
+    assert(r6->first.get() == 9);   // key
+    assert(r6->second.get() == 11); // value
+
+    // wrong hint: third element
+    Moveable mvkey7(10, 10.0);
+    Moveable mv7(12, 12.0);
+    std::same_as<R> decltype(auto) r7 = m.insert_or_assign(std::next(m.begin(), 2), std::move(mvkey7), std::move(mv7));
+    assert(m.size() == 13);
+    assert(mv7.moved());            // was moved from
+    assert(!mvkey7.moved());        // was not moved from
+    assert(r7->first == mvkey7);    // key
+    assert(r7->second.get() == 12); // value
+
+    Moveable mvkey8(11, 11.0);
+    Moveable mv8(13, 13.0);
+    std::same_as<R> decltype(auto) r8 = m.insert_or_assign(std::next(m.begin(), 2), std::move(mvkey8), std::move(mv8));
+    assert(m.size() == 14);
+    assert(mv8.moved());            // was moved from
+    assert(mvkey8.moved());         // was moved from
+    assert(r8->first.get() == 11);  // key
+    assert(r8->second.get() == 13); // value
+  }
+}
+
+int main(int, char**) {
+  test_cv_key<std::vector<int>, std::vector<Moveable>>();
+  test_cv_key<std::deque<int>, std::vector<Moveable>>();
+  test_cv_key<MinSequenceContainer<int>, MinSequenceContainer<Moveable>>();
+  test_cv_key<std::vector<int, min_allocator<int>>, std::vector<Moveable, min_allocator<Moveable>>>();
+
+  test_rv_key<std::vector<Moveable>, std::vector<Moveable>>();
+  test_rv_key<std::deque<Moveable>, std::vector<Moveable>>();
+  test_rv_key<MinSequenceContainer<Moveable>, MinSequenceContainer<Moveable>>();
+  test_rv_key<std::vector<Moveable, min_allocator<Moveable>>, std::vector<Moveable, min_allocator<Moveable>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_or_assign_transparent.pass.cpp

@@ -0,0 +1,259 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "MoveOnly.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+#include "../helpers.h"
+
+// template<class K, class M>
+//   pair<iterator, bool> insert_or_assign(K&& k, M&& obj);
+// template<class K, class M>
+//   iterator insert_or_assign(const_iterator hint, K&& k, M&& obj);
+
+// Constraints:
+// The qualified-id Compare::is_transparent is valid and denotes a type.
+// is_constructible_v<key_type, K> is true.
+// is_assignable_v<mapped_type&, M> is true.
+// is_constructible_v<mapped_type, M> is true.
+
+template <class Map, class K, class M>
+concept CanInsertOrAssign =
+    requires(Map map, K&& k, M&& m) { map.insert_or_assign(std::forward<K>(k), std::forward<M>(m)); };
+
+template <class Map, class K, class M>
+concept CanInsertOrAssignIter = requires(Map map, typename Map::const_iterator iter, K&& k, M&& m) {
+  map.insert_or_assign(iter, std::forward<K>(k), std::forward<M>(m));
+};
+
+template <class From>
+struct ConstructAndAssignFrom {
+  explicit ConstructAndAssignFrom(From);
+  ConstructAndAssignFrom& operator=(From);
+};
+
+template <class From>
+struct ConstructFrom {
+  explicit ConstructFrom(From);
+};
+
+template <class From>
+struct AssignFrom {
+  AssignFrom& operator=(From);
+};
+
+struct V {};
+
+static_assert(CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>, TransparentComparator>,
+                                ConvertibleTransparent<int>,
+                                V>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>, TransparentComparator>,
+                                 NonConvertibleTransparent<int>,
+                                 V>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>, NonTransparentComparator>,
+                                 NonConvertibleTransparent<int>,
+                                 V>);
+static_assert(!CanInsertOrAssign<std::flat_map<int, ConstructAndAssignFrom<V>, TransparentComparator>,
+                                 ConvertibleTransparent<int>,
+                                 int>);
+static_assert(
+    !CanInsertOrAssign<std::flat_map<int, ConstructFrom<V>, TransparentComparator>, ConvertibleTransparent<int>, V>);
+static_assert(
+    !CanInsertOrAssign<std::flat_map<int, AssignFrom<V>, TransparentComparator>, ConvertibleTransparent<int>, V>);
+
+static_assert(CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>, TransparentComparator>,
+                                    ConvertibleTransparent<int>,
+                                    V>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>, TransparentComparator>,
+                                     NonConvertibleTransparent<int>,
+                                     V>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>, NonTransparentComparator>,
+                                     NonConvertibleTransparent<int>,
+                                     V>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructAndAssignFrom<V>, TransparentComparator>,
+                                     ConvertibleTransparent<int>,
+                                     int>);
+static_assert(!CanInsertOrAssignIter<std::flat_map<int, ConstructFrom<V>, TransparentComparator>,
+                                     ConvertibleTransparent<int>,
+                                     V>);
+static_assert(
+    !CanInsertOrAssignIter<std::flat_map<int, AssignFrom<V>, TransparentComparator>, ConvertibleTransparent<int>, V>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, TransparentComparator, KeyContainer, ValueContainer>;
+  {
+    // pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
+    using R = std::pair<typename M::iterator, bool>;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(i, Moveable(i, (double)i));
+    assert(m.size() == 10);
+
+    for (int i = 0; i < 20; i += 2) {
+      Moveable mv(i + 1, i + 1);
+      std::same_as<R> decltype(auto) r1 = m.insert_or_assign(ConvertibleTransparent<int>{i}, std::move(mv));
+      assert(m.size() == 10);
+      assert(!r1.second);                      // was not inserted
+      assert(mv.moved());                      // was moved from
+      assert(r1.first->first == i);            // key
+      assert(r1.first->second.get() == i + 1); // value
+    }
+
+    Moveable mv1(5, 5.0);
+    std::same_as<R> decltype(auto) r2 = m.insert_or_assign(ConvertibleTransparent<int>{-1}, std::move(mv1));
+    assert(m.size() == 11);
+    assert(r2.second);                   // was inserted
+    assert(mv1.moved());                 // was moved from
+    assert(r2.first->first == -1);       // key
+    assert(r2.first->second.get() == 5); // value
+
+    Moveable mv2(9, 9.0);
+    std::same_as<R> decltype(auto) r3 = m.insert_or_assign(ConvertibleTransparent<int>{3}, std::move(mv2));
+    assert(m.size() == 12);
+    assert(r3.second);                   // was inserted
+    assert(mv2.moved());                 // was moved from
+    assert(r3.first->first == 3);        // key
+    assert(r3.first->second.get() == 9); // value
+
+    Moveable mv3(-1, 5.0);
+    std::same_as<R> decltype(auto) r4 = m.insert_or_assign(ConvertibleTransparent<int>{117}, std::move(mv3));
+    assert(m.size() == 13);
+    assert(r4.second);                    // was inserted
+    assert(mv3.moved());                  // was moved from
+    assert(r4.first->first == 117);       // key
+    assert(r4.first->second.get() == -1); // value
+  }
+  {
+    // iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
+    using R = M::iterator;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(i, Moveable(i, (double)i));
+    assert(m.size() == 10);
+    typename M::const_iterator it = m.find(2);
+
+    Moveable mv1(3, 3.0);
+    std::same_as<R> decltype(auto) r1 = m.insert_or_assign(it, ConvertibleTransparent<int>{2}, std::move(mv1));
+    assert(m.size() == 10);
+    assert(mv1.moved());           // was moved from
+    assert(r1->first == 2);        // key
+    assert(r1->second.get() == 3); // value
+
+    Moveable mv2(5, 5.0);
+    std::same_as<R> decltype(auto) r2 = m.insert_or_assign(it, ConvertibleTransparent<int>{3}, std::move(mv2));
+    assert(m.size() == 11);
+    assert(mv2.moved());           // was moved from
+    assert(r2->first == 3);        // key
+    assert(r2->second.get() == 5); // value
+
+    // wrong hint: begin()
+    Moveable mv3(7, 7.0);
+    std::same_as<R> decltype(auto) r3 = m.insert_or_assign(m.begin(), ConvertibleTransparent<int>{4}, std::move(mv3));
+    assert(m.size() == 11);
+    assert(mv3.moved());           // was moved from
+    assert(r3->first == 4);        // key
+    assert(r3->second.get() == 7); // value
+
+    Moveable mv4(9, 9.0);
+    std::same_as<R> decltype(auto) r4 = m.insert_or_assign(m.begin(), ConvertibleTransparent<int>{5}, std::move(mv4));
+    assert(m.size() == 12);
+    assert(mv4.moved());           // was moved from
+    assert(r4->first == 5);        // key
+    assert(r4->second.get() == 9); // value
+
+    // wrong hint: end()
+    Moveable mv5(11, 11.0);
+    std::same_as<R> decltype(auto) r5 = m.insert_or_assign(m.end(), ConvertibleTransparent<int>{6}, std::move(mv5));
+    assert(m.size() == 12);
+    assert(mv5.moved());            // was moved from
+    assert(r5->first == 6);         // key
+    assert(r5->second.get() == 11); // value
+
+    Moveable mv6(13, 13.0);
+    std::same_as<R> decltype(auto) r6 = m.insert_or_assign(m.end(), ConvertibleTransparent<int>{7}, std::move(mv6));
+    assert(m.size() == 13);
+    assert(mv6.moved());            // was moved from
+    assert(r6->first == 7);         // key
+    assert(r6->second.get() == 13); // value
+
+    // wrong hint: third element
+    Moveable mv7(15, 15.0);
+    std::same_as<R> decltype(auto) r7 =
+        m.insert_or_assign(std::next(m.begin(), 2), ConvertibleTransparent<int>{8}, std::move(mv7));
+    assert(m.size() == 13);
+    assert(mv7.moved());            // was moved from
+    assert(r7->first == 8);         // key
+    assert(r7->second.get() == 15); // value
+
+    Moveable mv8(17, 17.0);
+    std::same_as<R> decltype(auto) r8 =
+        m.insert_or_assign(std::next(m.begin(), 2), ConvertibleTransparent<int>{9}, std::move(mv8));
+    assert(m.size() == 14);
+    assert(mv8.moved());            // was moved from
+    assert(r8->first == 9);         // key
+    assert(r8->second.get() == 17); // value
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<Moveable>>();
+  test<std::deque<int>, std::vector<Moveable>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<Moveable>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<Moveable, min_allocator<Moveable>>>();
+
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    auto p = m.insert_or_assign(ConvertibleTransparent<int>{3}, 5);
+    assert(!p.second);
+    assert(transparent_used);
+  }
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    auto it = m.insert_or_assign(m.begin(), ConvertibleTransparent<int>{3}, 5);
+    assert(it->second == 5);
+    assert(transparent_used);
+  }
+
+  {
+    auto insert_or_assign = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      m.insert_or_assign(ConvertibleTransparent<Key>{key_arg}, value_arg);
+    };
+    test_emplace_exception_guarantee(insert_or_assign);
+  }
+
+  {
+    auto insert_or_assign_iter = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      m.insert_or_assign(m.begin(), ConvertibleTransparent<Key>{key_arg}, value_arg);
+    };
+    test_emplace_exception_guarantee(insert_or_assign_iter);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_range.pass.cpp

@@ -0,0 +1,109 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<container-compatible-range<value_type> R>
+//   void insert_range(R&& rg);
+
+#include <algorithm>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <ranges>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "MoveOnly.h"
+#include "test_macros.h"
+#include "test_iterators.h"
+#include "min_allocator.h"
+
+// test constraint container-compatible-range
+template <class M, class R>
+concept CanInsertRange = requires(M m, R&& r) { m.insert_range(std::forward<R>(r)); };
+
+using Map = std::flat_map<int, double>;
+
+static_assert(CanInsertRange<Map, std::ranges::subrange<std::pair<int, double>*>>);
+static_assert(CanInsertRange<Map, std::ranges::subrange<std::pair<short, double>*>>);
+static_assert(!CanInsertRange<Map, std::ranges::subrange<int*>>);
+static_assert(!CanInsertRange<Map, std::ranges::subrange<double*>>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+
+  {
+    using P                 = std::pair<int, int>;
+    using M                 = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+    using It                = forward_iterator<const P*>;
+    M m                     = {{10, 1}, {8, 2}, {5, 3}, {2, 4}, {1, 5}};
+    P ar[]                  = {{3, 1}, {1, 2}, {4, 3}, {1, 4}, {5, 5}, {9, 6}};
+    std::ranges::subrange r = {It(ar), It(ar + 6)};
+    static_assert(std::ranges::common_range<decltype(r)>);
+    m.insert_range(r);
+    assert((m == M{{1, 5}, {2, 4}, {3, 1}, {4, 3}, {5, 3}, {8, 2}, {9, 6}, {10, 1}}));
+  }
+  {
+    using P                 = std::pair<int, int>;
+    using M                 = std::flat_map<Key, Value, std::greater<>, KeyContainer, ValueContainer>;
+    using It                = cpp20_input_iterator<const P*>;
+    M m                     = {{8, 1}, {5, 2}, {3, 3}, {2, 4}};
+    P ar[]                  = {{3, 1}, {1, 2}, {4, 3}, {1, 4}, {5, 5}, {9, 6}};
+    std::ranges::subrange r = {It(ar), sentinel_wrapper<It>(It(ar + 6))};
+    static_assert(!std::ranges::common_range<decltype(r)>);
+    m.insert_range(r);
+    assert((m == M{{1, 2}, {2, 4}, {3, 3}, {4, 3}, {5, 2}, {8, 1}, {9, 6}}));
+  }
+  {
+    // The "uniquing" part uses the comparator, not operator==.
+    struct ModTen {
+      bool operator()(int a, int b) const { return (a % 10) < (b % 10); }
+    };
+    using P = std::pair<int, int>;
+    using M = std::flat_map<Key, Value, ModTen, KeyContainer, ValueContainer>;
+    M m     = {{21, 0}, {43, 0}, {15, 0}, {37, 0}};
+    P ar[]  = {{33, 1}, {18, 1}, {55, 1}, {18, 1}, {42, 1}};
+    m.insert_range(ar);
+    assert((m == M{{21, 0}, {42, 1}, {43, 0}, {15, 0}, {37, 0}, {18, 1}}));
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<int>>();
+  test<std::deque<int>, std::vector<int>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<int>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>();
+  {
+    // Items are forwarded correctly from the input range (P2767).
+    std::pair<MoveOnly, MoveOnly> a[] = {{3, 3}, {1, 1}, {4, 4}, {1, 1}, {5, 5}};
+    std::flat_map<MoveOnly, MoveOnly> m;
+    m.insert_range(a | std::views::as_rvalue);
+    std::pair<MoveOnly, MoveOnly> expected[] = {{1, 1}, {3, 3}, {4, 4}, {5, 5}};
+    assert(std::ranges::equal(m, expected));
+  }
+  {
+    // The element type of the range doesn't need to be std::pair (P2767).
+    std::pair<int, int> pa[] = {{3, 3}, {1, 1}, {4, 4}, {1, 1}, {5, 5}};
+    std::deque<std::reference_wrapper<std::pair<int, int>>> a(pa, pa + 5);
+    std::flat_map<int, int> m;
+    m.insert_range(a);
+    std::pair<int, int> expected[] = {{1, 1}, {3, 3}, {4, 4}, {5, 5}};
+    assert(std::ranges::equal(m, expected));
+  }
+  {
+    auto insert_func = [](auto& m, const auto& newValues) { m.insert_range(newValues); };
+    test_insert_range_exception_guarantee(insert_func);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_range_stability.pass.cpp

@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<container-compatible-range<value_type> R>
+//   void insert_range(R&& rg);
+//
+// libc++ uses stable_sort to ensure that flat_map's behavior matches map's,
+// in terms of which duplicate items are kept.
+// This tests a conforming extension.
+
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <flat_map>
+#include <random>
+#include <ranges>
+#include <map>
+#include <vector>
+#include <utility>
+
+#include "test_macros.h"
+
+struct Mod256 {
+  bool operator()(int x, int y) const { return (x % 256) < (y % 256); }
+};
+
+int main(int, char**) {
+  {
+    std::mt19937 randomness;
+    std::pair<uint16_t, uint16_t> pairs[400];
+    for (int i = 0; i < 400; ++i) {
+      uint16_t r = randomness();
+      pairs[i]   = {r, r};
+    }
+
+    std::map<uint16_t, uint16_t, Mod256> m(pairs, pairs + 200);
+    std::flat_map<uint16_t, uint16_t, Mod256> fm(std::sorted_unique, m.begin(), m.end());
+    assert(std::ranges::equal(fm, m));
+
+    fm.insert_range(std::views::counted(pairs + 200, 200));
+    m.insert(pairs + 200, pairs + 400);
+    assert(fm.size() == m.size());
+    LIBCPP_ASSERT(std::ranges::equal(fm, m));
+  }
+
+  {
+    std::vector<std::pair<int, int>> v{{1, 2}, {1, 3}};
+    std::flat_map<int, int> m;
+    m.insert_range(v);
+    assert(m.size() == 1);
+    LIBCPP_ASSERT(m[1] == 2);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_rv.pass.cpp

@@ -0,0 +1,124 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// class flat_map
+
+// pair<iterator, bool> insert( value_type&& v);
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "MoveOnly.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+#include "../helpers.h"
+
+template <class Container, class Pair>
+void do_insert_rv_test() {
+  using M = Container;
+  using P = Pair;
+  using R = std::pair<typename M::iterator, bool>;
+  M m;
+  std::same_as<R> decltype(auto) r = m.insert(P(2, 2));
+  assert(r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 1);
+  assert(r.first->first == 2);
+  assert(r.first->second == 2);
+
+  r = m.insert(P(1, 1));
+  assert(r.second);
+  assert(r.first == m.begin());
+  assert(m.size() == 2);
+  assert(r.first->first == 1);
+  assert(r.first->second == 1);
+
+  r = m.insert(P(3, 3));
+  assert(r.second);
+  assert(r.first == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r.first->first == 3);
+  assert(r.first->second == 3);
+
+  r = m.insert(P(3, 3));
+  assert(!r.second);
+  assert(r.first == std::ranges::prev(m.end()));
+  assert(m.size() == 3);
+  assert(r.first->first == 3);
+  assert(r.first->second == 3);
+}
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, TransparentComparator, KeyContainer, ValueContainer>;
+
+  using P  = std::pair<Key, Value>;
+  using CP = std::pair<const Key, Value>;
+
+  do_insert_rv_test<M, P>();
+  do_insert_rv_test<M, CP>();
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<MoveOnly>>();
+  test<std::deque<int>, std::vector<MoveOnly>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<MoveOnly>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<MoveOnly, min_allocator<MoveOnly>>>();
+
+  {
+    using M = std::flat_map<int, MoveOnly>;
+    using R = std::pair<M::iterator, bool>;
+    M m;
+    R r = m.insert({2, MoveOnly(2)});
+    assert(r.second);
+    assert(r.first == m.begin());
+    assert(m.size() == 1);
+    assert(r.first->first == 2);
+    assert(r.first->second == 2);
+
+    r = m.insert({1, MoveOnly(1)});
+    assert(r.second);
+    assert(r.first == m.begin());
+    assert(m.size() == 2);
+    assert(r.first->first == 1);
+    assert(r.first->second == 1);
+
+    r = m.insert({3, MoveOnly(3)});
+    assert(r.second);
+    assert(r.first == std::ranges::prev(m.end()));
+    assert(m.size() == 3);
+    assert(r.first->first == 3);
+    assert(r.first->second == 3);
+
+    r = m.insert({3, MoveOnly(3)});
+    assert(!r.second);
+    assert(r.first == std::ranges::prev(m.end()));
+    assert(m.size() == 3);
+    assert(r.first->first == 3);
+    assert(r.first->second == 3);
+  }
+  {
+    auto insert_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap    = std::decay_t<decltype(m)>;
+      using value_type = typename FlatMap::value_type;
+      value_type p(std::piecewise_construct, std::tuple(key_arg), std::tuple(value_arg));
+      m.insert(std::move(p));
+    };
+    test_emplace_exception_guarantee(insert_func);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_sorted_initializer_list.pass.cpp

@@ -0,0 +1,66 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// void insert(initializer_list<value_type> il);
+
+#include <flat_map>
+#include <cassert>
+#include <functional>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  using V = std::pair<const Key, Value>;
+  M m     = {{1, 1}, {1, 1.5}, {1, 2}, {3, 1}, {3, 1.5}, {3, 2}};
+  m.insert(std::sorted_unique,
+           {
+               {0, 1},
+               {1, 2},
+               {2, 1},
+               {4, 1},
+           });
+  assert(m.size() == 5);
+  assert(std::distance(m.begin(), m.end()) == 5);
+  assert(*m.begin() == V(0, 1));
+  assert(*std::next(m.begin()) == V(1, 1));
+  assert(*std::next(m.begin(), 2) == V(2, 1));
+  assert(*std::next(m.begin(), 3) == V(3, 1));
+  assert(*std::next(m.begin(), 4) == V(4, 1));
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto insert_func = [](auto& m, const auto& newValues) {
+      using FlatMap                        = std::decay_t<decltype(m)>;
+      using value_type                     = typename FlatMap::value_type;
+      std::initializer_list<value_type> il = {{newValues[0].first, newValues[0].second}};
+      m.insert(std::sorted_unique, il);
+    };
+    test_insert_range_exception_guarantee(insert_func);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_sorted_iter_iter.pass.cpp

@@ -0,0 +1,86 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template <class InputIterator>
+//   void insert(sorted_unique_t, InputIterator first, InputIterator last);
+
+#include <flat_map>
+#include <cassert>
+#include <functional>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "test_iterators.h"
+#include "min_allocator.h"
+
+// test constraint InputIterator
+template <class M, class... Args>
+concept CanInsert = requires(M m, Args&&... args) { m.insert(std::forward<Args>(args)...); };
+
+using Map  = std::flat_map<int, int>;
+using Pair = std::pair<int, int>;
+
+static_assert(CanInsert<Map, std::sorted_unique_t, Pair*, Pair*>);
+static_assert(CanInsert<Map, std::sorted_unique_t, cpp17_input_iterator<Pair*>, cpp17_input_iterator<Pair*>>);
+static_assert(!CanInsert<Map, std::sorted_unique_t, int, int>);
+static_assert(!CanInsert<Map, std::sorted_unique_t, cpp20_input_iterator<Pair*>, cpp20_input_iterator<Pair*>>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using P     = std::pair<Key, Value>;
+
+  P ar1[] = {
+      P(1, 1),
+      P(2, 1),
+      P(3, 1),
+  };
+
+  P ar2[] = {
+      P(0, 1),
+      P(2, 2),
+      P(4, 1),
+  };
+
+  M m;
+  m.insert(
+      std::sorted_unique, cpp17_input_iterator<P*>(ar1), cpp17_input_iterator<P*>(ar1 + sizeof(ar1) / sizeof(ar1[0])));
+  assert(m.size() == 3);
+  M expected{{1, 1}, {2, 1}, {3, 1}};
+  assert(m == expected);
+
+  m.insert(
+      std::sorted_unique, cpp17_input_iterator<P*>(ar2), cpp17_input_iterator<P*>(ar2 + sizeof(ar2) / sizeof(ar2[0])));
+  assert(m.size() == 5);
+  M expected2{{0, 1}, {1, 1}, {2, 1}, {3, 1}, {4, 1}};
+  assert(m == expected2);
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    auto insert_func = [](auto& m, const auto& newValues) {
+      m.insert(std::sorted_unique, newValues.begin(), newValues.end());
+    };
+    test_insert_range_exception_guarantee(insert_func);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/insert_transparent.pass.cpp

@@ -0,0 +1,167 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class K> pair<iterator, bool> insert(P&& x);
+// template<class K> iterator insert(const_iterator hint, P&& x);
+
+#include <algorithm>
+#include <compare>
+#include <concepts>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <tuple>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "test_iterators.h"
+#include "min_allocator.h"
+
+// Constraints: is_constructible_v<pair<key_type, mapped_type>, P> is true.
+template <class M, class... Args>
+concept CanInsert = requires(M m, Args&&... args) { m.insert(std::forward<Args>(args)...); };
+
+using Map  = std::flat_map<int, double>;
+using Iter = Map::const_iterator;
+
+static_assert(CanInsert<Map, std::pair<short, double>&&>);
+static_assert(CanInsert<Map, Iter, std::pair<short, double>&&>);
+static_assert(CanInsert<Map, std::tuple<short, double>&&>);
+static_assert(CanInsert<Map, Iter, std::tuple<short, double>&&>);
+static_assert(!CanInsert<Map, int>);
+static_assert(!CanInsert<Map, Iter, int>);
+
+static int expensive_comparisons = 0;
+static int cheap_comparisons     = 0;
+
+struct CompareCounter {
+  int i_ = 0;
+  CompareCounter(int i) : i_(i) {}
+  friend auto operator<=>(const CompareCounter& x, const CompareCounter& y) {
+    expensive_comparisons += 1;
+    return x.i_ <=> y.i_;
+  }
+  bool operator==(const CompareCounter&) const = default;
+  friend auto operator<=>(const CompareCounter& x, int y) {
+    cheap_comparisons += 1;
+    return x.i_ <=> y;
+  }
+};
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  const std::pair<int, int> expected[] = {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}};
+  {
+    // insert(P&&)
+    //   Unlike flat_set, here we can't use key_compare to compare value_type versus P,
+    //   so we must eagerly convert to value_type.
+    M m                   = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    expensive_comparisons = 0;
+    cheap_comparisons     = 0;
+    std::same_as<std::pair<typename M::iterator, bool>> auto p =
+        m.insert(std::make_pair(3, 3)); // conversion happens first
+    assert(expensive_comparisons >= 2);
+    assert(cheap_comparisons == 0);
+    assert(p == std::make_pair(m.begin() + 2, true));
+    assert(std::ranges::equal(m, expected));
+  }
+  {
+    // insert(const_iterator, P&&)
+    M m                                        = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    expensive_comparisons                      = 0;
+    cheap_comparisons                          = 0;
+    std::same_as<typename M::iterator> auto it = m.insert(m.begin(), std::make_pair(3, 3));
+    assert(expensive_comparisons >= 2);
+    assert(cheap_comparisons == 0);
+    assert(it == m.begin() + 2);
+    assert(std::ranges::equal(m, expected));
+  }
+  {
+    // insert(value_type&&)
+    M m                   = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    expensive_comparisons = 0;
+    cheap_comparisons     = 0;
+    std::same_as<std::pair<typename M::iterator, bool>> auto p =
+        m.insert(std::make_pair(3, 3)); // conversion happens last
+    assert(expensive_comparisons >= 2);
+    assert(cheap_comparisons == 0);
+    assert(p == std::make_pair(m.begin() + 2, true));
+    assert(std::ranges::equal(m, expected));
+  }
+  {
+    // insert(const_iterator, value_type&&)
+    M m                                        = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    expensive_comparisons                      = 0;
+    cheap_comparisons                          = 0;
+    std::same_as<typename M::iterator> auto it = m.insert(m.begin(), std::make_pair(3, 3));
+    assert(expensive_comparisons >= 2);
+    assert(cheap_comparisons == 0);
+    assert(it == m.begin() + 2);
+    assert(std::ranges::equal(m, expected));
+  }
+  {
+    // emplace(Args&&...)
+    M m                   = {{1, 1}, {2, 2}, {4, 4}, {5, 5}};
+    expensive_comparisons = 0;
+    cheap_comparisons     = 0;
+    std::same_as<std::pair<typename M::iterator, bool>> auto p =
+        m.emplace(std::make_pair(3, 3)); // conversion happens first
+    assert(expensive_comparisons >= 2);
+    assert(cheap_comparisons == 0);
+    assert(p == std::make_pair(m.begin() + 2, true));
+    assert(std::ranges::equal(m, expected));
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<CompareCounter>, std::vector<double>>();
+  test<std::deque<CompareCounter>, std::vector<double>>();
+  test<MinSequenceContainer<CompareCounter>, MinSequenceContainer<double>>();
+  test<std::vector<CompareCounter, min_allocator<CompareCounter>>, std::vector<double, min_allocator<double>>>();
+
+  {
+    // no ambiguity between insert(pos, P&&) and insert(first, last)
+    using M = std::flat_map<int, int>;
+    struct Evil {
+      operator M::value_type() const;
+      operator M::const_iterator() const;
+    };
+    std::flat_map<int, int> m;
+    ASSERT_SAME_TYPE(decltype(m.insert(Evil())), std::pair<M::iterator, bool>);
+    ASSERT_SAME_TYPE(decltype(m.insert(m.begin(), Evil())), M::iterator);
+    ASSERT_SAME_TYPE(decltype(m.insert(m.begin(), m.end())), void);
+  }
+  {
+    auto insert_func = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap    = std::decay_t<decltype(m)>;
+      using tuple_type = std::tuple<typename FlatMap::key_type, typename FlatMap::mapped_type>;
+      tuple_type t(key_arg, value_arg);
+      m.insert(t);
+    };
+    test_emplace_exception_guarantee(insert_func);
+  }
+  {
+    auto insert_func_iter = [](auto& m, auto key_arg, auto value_arg) {
+      using FlatMap    = std::decay_t<decltype(m)>;
+      using tuple_type = std::tuple<typename FlatMap::key_type, typename FlatMap::mapped_type>;
+      tuple_type t(key_arg, value_arg);
+      m.insert(m.begin(), t);
+    };
+    test_emplace_exception_guarantee(insert_func_iter);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/replace.pass.cpp

@@ -0,0 +1,80 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// void replace(key_container_type&& key_cont, mapped_container_type&& mapped_cont);
+
+#include <algorithm>
+#include <deque>
+#include <concepts>
+#include <flat_map>
+#include <functional>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class T, class... Args>
+concept CanReplace = requires(T t, Args&&... args) { t.replace(std::forward<Args>(args)...); };
+
+using Map = std::flat_map<int, int>;
+static_assert(CanReplace<Map, std::vector<int>, std::vector<int>>);
+static_assert(!CanReplace<Map, const std::vector<int>&, std::vector<int>>);
+static_assert(!CanReplace<Map, std::vector<int>, const std::vector<int>&>);
+static_assert(!CanReplace<Map, const std::vector<int>&, const std::vector<int>&>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  M m                       = M({1, 2, 3}, {4, 5, 6});
+  KeyContainer new_keys     = {7, 8};
+  ValueContainer new_values = {9, 10};
+  auto expected_keys        = new_keys;
+  auto expected_values      = new_values;
+  m.replace(std::move(new_keys), std::move(new_values));
+  assert(m.size() == 2);
+  assert(std::ranges::equal(m.keys(), expected_keys));
+  assert(std::ranges::equal(m.values(), expected_values));
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    using KeyContainer   = std::vector<int>;
+    using ValueContainer = ThrowOnMoveContainer<int>;
+    using M              = std::flat_map<int, int, std::ranges::less, KeyContainer, ValueContainer>;
+
+    M m;
+    m.emplace(1, 1);
+    m.emplace(2, 2);
+    try {
+      KeyContainer new_keys{3, 4};
+      ValueContainer new_values{5, 6};
+      m.replace(std::move(new_keys), std::move(new_values));
+      assert(false);
+    } catch (int) {
+      check_invariant(m);
+      // In libc++, we clear the map
+      LIBCPP_ASSERT(m.size() == 0);
+    }
+#endif
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/swap_exception.pass.cpp

@@ -0,0 +1,78 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// `check_assertion.h` requires Unix headers and regex support.
+// REQUIRES: has-unix-headers
+// UNSUPPORTED: no-localization
+// UNSUPPORTED: no-exceptions
+
+// <flat_map>
+
+// void swap(flat_map& y) noexcept;
+// friend void swap(flat_map& x, flat_map& y) noexcept
+
+// Test that std::terminate is called if any exception is thrown during swap
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+#include <functional>
+#include <vector>
+
+#include "test_macros.h"
+#include "../helpers.h"
+#include "check_assertion.h"
+
+template <class F>
+void test_swap_exception_guarantee([[maybe_unused]] F&& swap_function) {
+  {
+    // key swap throws
+    using KeyContainer   = ThrowOnMoveContainer<int>;
+    using ValueContainer = std::vector<int>;
+    using M              = std::flat_map<int, int, TransparentComparator, KeyContainer, ValueContainer>;
+
+    M m1, m2;
+    m1.emplace(1, 1);
+    m1.emplace(2, 2);
+    m2.emplace(3, 3);
+    m2.emplace(4, 4);
+    // swap is noexcept
+    EXPECT_STD_TERMINATE([&] { swap_function(m1, m2); });
+  }
+
+  {
+    // value swap throws
+    using KeyContainer   = std::vector<int>;
+    using ValueContainer = ThrowOnMoveContainer<int>;
+    using M              = std::flat_map<int, int, TransparentComparator, KeyContainer, ValueContainer>;
+
+    M m1, m2;
+    m1.emplace(1, 1);
+    m1.emplace(2, 2);
+    m2.emplace(3, 3);
+    m2.emplace(4, 4);
+
+    // swap is noexcept
+    EXPECT_STD_TERMINATE([&] { swap_function(m1, m2); });
+  }
+}
+
+int main(int, char**) {
+  {
+    auto swap_func = [](auto& m1, auto& m2) { swap(m1, m2); };
+    test_swap_exception_guarantee(swap_func);
+  }
+
+  {
+    auto swap_func = [](auto& m1, auto& m2) { m1.swap(m2); };
+    test_swap_exception_guarantee(swap_func);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/swap_free.pass.cpp

@@ -0,0 +1,97 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// friend void swap(flat_map& x, flat_map& y) noexcept
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "MoveOnly.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+#include "../helpers.h"
+
+// test noexcept
+
+template <class T>
+concept NoExceptAdlSwap = requires(T t1, T t2) {
+  { swap(t1, t2) } noexcept;
+};
+
+static_assert(NoExceptAdlSwap<std::flat_map<int, int>>);
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+static_assert(
+    NoExceptAdlSwap<std::flat_map<int, int, std::less<int>, ThrowOnMoveContainer<int>, ThrowOnMoveContainer<int>>>);
+#endif
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using V     = std::pair<const Key, Value>;
+
+  {
+    M m1;
+    M m2;
+    M m1_save = m1;
+    M m2_save = m2;
+    swap(m1, m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+  {
+    V ar2[] = {V(5, 5), V(6, 6), V(7, 7), V(8, 8), V(9, 9), V(10, 10), V(11, 11), V(12, 12)};
+    M m1;
+    M m2(ar2, ar2 + sizeof(ar2) / sizeof(ar2[0]));
+    M m1_save = m1;
+    M m2_save = m2;
+    swap(m1, m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+  {
+    V ar1[] = {V(1, 1), V(2, 2), V(3, 3), V(4, 4)};
+    M m1(ar1, ar1 + sizeof(ar1) / sizeof(ar1[0]));
+    M m2;
+    M m1_save = m1;
+    M m2_save = m2;
+    swap(m1, m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+  {
+    V ar1[] = {V(1, 1), V(2, 2), V(3, 3), V(4, 4)};
+    V ar2[] = {V(5, 5), V(6, 6), V(7, 7), V(8, 8), V(9, 9), V(10, 10), V(11, 11), V(12, 12)};
+    M m1(ar1, ar1 + sizeof(ar1) / sizeof(ar1[0]));
+    M m2(ar2, ar2 + sizeof(ar2) / sizeof(ar2[0]));
+    M m1_save = m1;
+    M m2_save = m2;
+    swap(m1, m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/swap_member.pass.cpp

@@ -0,0 +1,95 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// void swap(flat_map& y) noexcept;
+
+#include <flat_map>
+#include <cassert>
+#include <deque>
+#include <functional>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "MoveOnly.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+#include "../helpers.h"
+
+// test noexcept
+
+template <class T>
+concept NoExceptMemberSwap = requires(T t1, T t2) {
+  { t1.swap(t2) } noexcept;
+};
+
+static_assert(NoExceptMemberSwap<std::flat_map<int, int>>);
+#ifndef TEST_HAS_NO_EXCEPTIONS
+static_assert(
+    NoExceptMemberSwap<std::flat_map<int, int, std::less<int>, ThrowOnMoveContainer<int>, ThrowOnMoveContainer<int>>>);
+#endif
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+  using V     = std::pair<const Key, Value>;
+  {
+    M m1;
+    M m2;
+    M m1_save = m1;
+    M m2_save = m2;
+    m1.swap(m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+  {
+    V ar2[] = {V(5, 5), V(6, 6), V(7, 7), V(8, 8), V(9, 9), V(10, 10), V(11, 11), V(12, 12)};
+    M m1;
+    M m2(ar2, ar2 + sizeof(ar2) / sizeof(ar2[0]));
+    M m1_save = m1;
+    M m2_save = m2;
+    m1.swap(m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+  {
+    V ar1[] = {V(1, 1), V(2, 2), V(3, 3), V(4, 4)};
+    M m1(ar1, ar1 + sizeof(ar1) / sizeof(ar1[0]));
+    M m2;
+    M m1_save = m1;
+    M m2_save = m2;
+    m1.swap(m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+  {
+    V ar1[] = {V(1, 1), V(2, 2), V(3, 3), V(4, 4)};
+    V ar2[] = {V(5, 5), V(6, 6), V(7, 7), V(8, 8), V(9, 9), V(10, 10), V(11, 11), V(12, 12)};
+    M m1(ar1, ar1 + sizeof(ar1) / sizeof(ar1[0]));
+    M m2(ar2, ar2 + sizeof(ar2) / sizeof(ar2[0]));
+    M m1_save = m1;
+    M m2_save = m2;
+    m1.swap(m2);
+    assert(m1 == m2_save);
+    assert(m2 == m1_save);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<double>>();
+  test<std::deque<int>, std::vector<double>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<double>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<double, min_allocator<double>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/try_emplace.pass.cpp

@@ -0,0 +1,246 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class... Args>
+//   pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
+// template<class... Args>
+//   pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
+// template<class... Args>
+//   iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
+// template<class... Args>
+//   iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
+
+#include <flat_map>
+#include <cassert>
+#include <functional>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "../helpers.h"
+#include "min_allocator.h"
+#include "../../../Emplaceable.h"
+
+// Constraints: is_constructible_v<mapped_type, Args...> is true.
+template <class M, class... Args>
+concept CanTryEmplace = requires(M m, Args&&... args) { m.try_emplace(std::forward<Args>(args)...); };
+
+using Map  = std::flat_map<Emplaceable, Emplaceable>;
+using Iter = typename Map::const_iterator;
+static_assert(!CanTryEmplace<Map>);
+
+static_assert(CanTryEmplace<Map, const Emplaceable&>);
+static_assert(CanTryEmplace<Map, const Emplaceable&, Emplaceable>);
+static_assert(CanTryEmplace<Map, const Emplaceable&, int, double>);
+static_assert(!CanTryEmplace<Map, const Emplaceable&, const Emplaceable&>);
+static_assert(!CanTryEmplace<Map, const Emplaceable&, int>);
+
+static_assert(CanTryEmplace<Map, Emplaceable>);
+static_assert(CanTryEmplace<Map, Emplaceable, Emplaceable>);
+static_assert(CanTryEmplace<Map, Emplaceable, int, double>);
+static_assert(!CanTryEmplace<Map, Emplaceable, const Emplaceable&>);
+static_assert(!CanTryEmplace<Map, Emplaceable, int>);
+
+static_assert(CanTryEmplace<Map, Iter, const Emplaceable&>);
+static_assert(CanTryEmplace<Map, Iter, const Emplaceable&, Emplaceable>);
+static_assert(CanTryEmplace<Map, Iter, const Emplaceable&, int, double>);
+static_assert(!CanTryEmplace<Map, Iter, const Emplaceable&, const Emplaceable&>);
+static_assert(!CanTryEmplace<Map, Iter, const Emplaceable&, int>);
+
+static_assert(CanTryEmplace<Map, Iter, Emplaceable>);
+static_assert(CanTryEmplace<Map, Iter, Emplaceable, Emplaceable>);
+static_assert(CanTryEmplace<Map, Iter, Emplaceable, int, double>);
+static_assert(!CanTryEmplace<Map, Iter, Emplaceable, const Emplaceable&>);
+static_assert(!CanTryEmplace<Map, Iter, Emplaceable, int>);
+
+template <class KeyContainer, class ValueContainer>
+void test_ck() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  { // pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
+    using R = std::pair<typename M::iterator, bool>;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(i, Moveable(i, (double)i));
+
+    assert(m.size() == 10);
+
+    Moveable mv1(3, 3.0);
+    for (int i = 0; i < 20; i += 2) {
+      std::same_as<R> decltype(auto) r = m.try_emplace(i, std::move(mv1));
+      assert(m.size() == 10);
+      assert(!r.second);           // was not inserted
+      assert(!mv1.moved());        // was not moved from
+      assert(r.first->first == i); // key
+    }
+
+    std::same_as<R> decltype(auto) r2 = m.try_emplace(-1, std::move(mv1));
+    assert(m.size() == 11);
+    assert(r2.second);                   // was inserted
+    assert(mv1.moved());                 // was moved from
+    assert(r2.first->first == -1);       // key
+    assert(r2.first->second.get() == 3); // value
+
+    Moveable mv2(5, 3.0);
+    std::same_as<R> decltype(auto) r3 = m.try_emplace(5, std::move(mv2));
+    assert(m.size() == 12);
+    assert(r3.second);                   // was inserted
+    assert(mv2.moved());                 // was moved from
+    assert(r3.first->first == 5);        // key
+    assert(r3.first->second.get() == 5); // value
+
+    Moveable mv3(-1, 3.0);
+    std::same_as<R> decltype(auto) r4 = m.try_emplace(117, std::move(mv2));
+    assert(m.size() == 13);
+    assert(r4.second);                    // was inserted
+    assert(mv2.moved());                  // was moved from
+    assert(r4.first->first == 117);       // key
+    assert(r4.first->second.get() == -1); // value
+  }
+
+  { // iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
+    using R = typename M::iterator;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.try_emplace(i, Moveable(i, (double)i));
+    assert(m.size() == 10);
+    typename M::const_iterator it = m.find(2);
+
+    Moveable mv1(3, 3.0);
+    for (int i = 0; i < 20; i += 2) {
+      std::same_as<R> decltype(auto) r1 = m.try_emplace(it, i, std::move(mv1));
+      assert(m.size() == 10);
+      assert(!mv1.moved());          // was not moved from
+      assert(r1->first == i);        // key
+      assert(r1->second.get() == i); // value
+    }
+
+    std::same_as<R> decltype(auto) r2 = m.try_emplace(it, 3, std::move(mv1));
+    assert(m.size() == 11);
+    assert(mv1.moved());           // was moved from
+    assert(r2->first == 3);        // key
+    assert(r2->second.get() == 3); // value
+  }
+}
+
+template <class KeyContainer, class ValueContainer>
+void test_rk() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  { // pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
+    using R = std::pair<typename M::iterator, bool>;
+    M m;
+    for (int i = 0; i < 20; i += 2) {
+      m.emplace(Moveable(i, (double)i), Moveable(i + 1, (double)i + 1));
+    }
+    assert(m.size() == 10);
+
+    Moveable mvkey1(2, 2.0);
+    Moveable mv1(4, 4.0);
+    std::same_as<R> decltype(auto) r1 = m.try_emplace(std::move(mvkey1), std::move(mv1));
+    assert(m.size() == 10);
+    assert(!r1.second);                // was not inserted
+    assert(!mv1.moved());              // was not moved from
+    assert(!mvkey1.moved());           // was not moved from
+    assert(r1.first->first == mvkey1); // key
+
+    Moveable mvkey2(3, 3.0);
+    std::same_as<R> decltype(auto) r2 = m.try_emplace(std::move(mvkey2), std::move(mv1));
+    assert(m.size() == 11);
+    assert(r2.second);                   // was inserted
+    assert(mv1.moved());                 // was moved from
+    assert(mvkey2.moved());              // was moved from
+    assert(r2.first->first.get() == 3);  // key
+    assert(r2.first->second.get() == 4); // value
+  }
+
+  { // iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
+    using R = typename M::iterator;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(Moveable(i, (double)i), Moveable(i + 1, (double)i + 1));
+    assert(m.size() == 10);
+    typename M::const_iterator it = std::next(m.cbegin());
+
+    Moveable mvkey1(2, 2.0);
+    Moveable mv1(4, 4.0);
+    std::same_as<R> decltype(auto) r1 = m.try_emplace(it, std::move(mvkey1), std::move(mv1));
+    assert(m.size() == 10);
+    assert(!mv1.moved());        // was not moved from
+    assert(!mvkey1.moved());     // was not moved from
+    assert(r1->first == mvkey1); // key
+
+    Moveable mvkey2(3, 3.0);
+    std::same_as<R> decltype(auto) r2 = m.try_emplace(it, std::move(mvkey2), std::move(mv1));
+    assert(m.size() == 11);
+    assert(mv1.moved());           // was moved from
+    assert(mvkey2.moved());        // was moved from
+    assert(r2->first.get() == 3);  // key
+    assert(r2->second.get() == 4); // value
+  }
+}
+
+int main(int, char**) {
+  test_ck<std::vector<int>, std::vector<Moveable>>();
+  test_ck<std::deque<int>, std::vector<Moveable>>();
+  test_ck<MinSequenceContainer<int>, MinSequenceContainer<Moveable>>();
+  test_ck<std::vector<int, min_allocator<int>>, std::vector<Moveable, min_allocator<Moveable>>>();
+
+  test_rk<std::vector<Moveable>, std::vector<Moveable>>();
+  test_rk<std::deque<Moveable>, std::vector<Moveable>>();
+  test_rk<MinSequenceContainer<Moveable>, MinSequenceContainer<Moveable>>();
+  test_rk<std::vector<Moveable, min_allocator<Moveable>>, std::vector<Moveable, min_allocator<Moveable>>>();
+
+  {
+    auto try_emplace_ck = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      const Key key{key_arg};
+      m.try_emplace(key, value_arg);
+    };
+    test_emplace_exception_guarantee(try_emplace_ck);
+  }
+
+  {
+    auto try_emplace_rk = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      m.try_emplace(Key{key_arg}, value_arg);
+    };
+    test_emplace_exception_guarantee(try_emplace_rk);
+  }
+
+  {
+    auto try_emplace_iter_ck = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      const Key key{key_arg};
+      m.try_emplace(m.begin(), key, value_arg);
+    };
+    test_emplace_exception_guarantee(try_emplace_iter_ck);
+  }
+
+  {
+    auto try_emplace_iter_rk = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      m.try_emplace(m.begin(), Key{key_arg}, value_arg);
+    };
+    test_emplace_exception_guarantee(try_emplace_iter_rk);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.modifiers/try_emplace_transparent.pass.cpp

@@ -0,0 +1,182 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class K, class... Args>
+//   pair<iterator, bool> try_emplace(K&& k, Args&&... args);
+// template<class K, class... Args>
+//   iterator try_emplace(const_iterator hint, K&& k, Args&&... args);
+
+#include <flat_map>
+#include <cassert>
+#include <functional>
+#include <deque>
+#include <vector>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "../helpers.h"
+#include "min_allocator.h"
+#include "../../../Emplaceable.h"
+
+// Constraints:
+// The qualified-id Compare::is_transparent is valid and denotes a type.
+// is_constructible_v<key_type, K> is true.
+// is_constructible_v<mapped_type, Args...> is true.
+// For the first overload, is_convertible_v<K&&, const_iterator> and is_convertible_v<K&&, iterator> are both false
+template <class M, class... Args>
+concept CanTryEmplace = requires(M m, Args&&... args) { m.try_emplace(std::forward<Args>(args)...); };
+
+using TransparentMap    = std::flat_map<int, Emplaceable, TransparentComparator>;
+using NonTransparentMap = std::flat_map<int, Emplaceable, NonTransparentComparator>;
+
+using TransparentMapIter      = typename TransparentMap::iterator;
+using TransparentMapConstIter = typename TransparentMap::const_iterator;
+
+static_assert(!CanTryEmplace<TransparentMap>);
+static_assert(!CanTryEmplace<NonTransparentMap>);
+
+static_assert(CanTryEmplace<TransparentMap, ConvertibleTransparent<int>>);
+static_assert(CanTryEmplace<TransparentMap, ConvertibleTransparent<int>, Emplaceable>);
+static_assert(CanTryEmplace<TransparentMap, ConvertibleTransparent<int>, int, double>);
+static_assert(!CanTryEmplace<TransparentMap, ConvertibleTransparent<int>, const Emplaceable&>);
+static_assert(!CanTryEmplace<TransparentMap, ConvertibleTransparent<int>, int>);
+static_assert(!CanTryEmplace<TransparentMap, NonConvertibleTransparent<int>, Emplaceable>);
+static_assert(!CanTryEmplace<NonTransparentMap, NonConvertibleTransparent<int>, Emplaceable>);
+static_assert(!CanTryEmplace<TransparentMap, ConvertibleTransparent<int>, int>);
+static_assert(!CanTryEmplace<TransparentMap, TransparentMapIter, Emplaceable>);
+static_assert(!CanTryEmplace<TransparentMap, TransparentMapConstIter, Emplaceable>);
+
+static_assert(CanTryEmplace<TransparentMap, TransparentMapConstIter, ConvertibleTransparent<int>>);
+static_assert(CanTryEmplace<TransparentMap, TransparentMapConstIter, ConvertibleTransparent<int>, Emplaceable>);
+static_assert(CanTryEmplace<TransparentMap, TransparentMapConstIter, ConvertibleTransparent<int>, int, double>);
+static_assert(!CanTryEmplace<TransparentMap, TransparentMapConstIter, ConvertibleTransparent<int>, const Emplaceable&>);
+static_assert(!CanTryEmplace<TransparentMap, TransparentMapConstIter, ConvertibleTransparent<int>, int>);
+static_assert(!CanTryEmplace<TransparentMap, TransparentMapConstIter, NonConvertibleTransparent<int>, Emplaceable>);
+static_assert(!CanTryEmplace<NonTransparentMap, TransparentMapConstIter, NonConvertibleTransparent<int>, Emplaceable>);
+static_assert(!CanTryEmplace<TransparentMap, TransparentMapConstIter, ConvertibleTransparent<int>, int>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, TransparentComparator, KeyContainer, ValueContainer>;
+
+  { // pair<iterator, bool> try_emplace(K&& k, Args&&... args);
+    using R = std::pair<typename M::iterator, bool>;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.emplace(i, Moveable(i, (double)i));
+
+    assert(m.size() == 10);
+
+    Moveable mv1(3, 3.0);
+    for (int i = 0; i < 20; i += 2) {
+      std::same_as<R> decltype(auto) r = m.try_emplace(ConvertibleTransparent<int>{i}, std::move(mv1));
+      assert(m.size() == 10);
+      assert(!r.second);           // was not inserted
+      assert(!mv1.moved());        // was not moved from
+      assert(r.first->first == i); // key
+    }
+
+    std::same_as<R> decltype(auto) r2 = m.try_emplace(ConvertibleTransparent<int>{-1}, std::move(mv1));
+    assert(m.size() == 11);
+    assert(r2.second);                   // was inserted
+    assert(mv1.moved());                 // was moved from
+    assert(r2.first->first == -1);       // key
+    assert(r2.first->second.get() == 3); // value
+
+    Moveable mv2(5, 3.0);
+    std::same_as<R> decltype(auto) r3 = m.try_emplace(ConvertibleTransparent<int>{5}, std::move(mv2));
+    assert(m.size() == 12);
+    assert(r3.second);                   // was inserted
+    assert(mv2.moved());                 // was moved from
+    assert(r3.first->first == 5);        // key
+    assert(r3.first->second.get() == 5); // value
+
+    Moveable mv3(-1, 3.0);
+    std::same_as<R> decltype(auto) r4 = m.try_emplace(ConvertibleTransparent<int>{117}, std::move(mv2));
+    assert(m.size() == 13);
+    assert(r4.second);                    // was inserted
+    assert(mv2.moved());                  // was moved from
+    assert(r4.first->first == 117);       // key
+    assert(r4.first->second.get() == -1); // value
+  }
+
+  { // iterator try_emplace(const_iterator hint, K&& k, Args&&... args);
+    using R = typename M::iterator;
+    M m;
+    for (int i = 0; i < 20; i += 2)
+      m.try_emplace(i, Moveable(i, (double)i));
+    assert(m.size() == 10);
+    typename M::const_iterator it = m.find(2);
+
+    Moveable mv1(3, 3.0);
+    for (int i = 0; i < 20; i += 2) {
+      std::same_as<R> decltype(auto) r1 = m.try_emplace(it, ConvertibleTransparent<int>{i}, std::move(mv1));
+      assert(m.size() == 10);
+      assert(!mv1.moved());          // was not moved from
+      assert(r1->first == i);        // key
+      assert(r1->second.get() == i); // value
+    }
+
+    std::same_as<R> decltype(auto) r2 = m.try_emplace(it, ConvertibleTransparent<int>{3}, std::move(mv1));
+    assert(m.size() == 11);
+    assert(mv1.moved());           // was moved from
+    assert(r2->first == 3);        // key
+    assert(r2->second.get() == 3); // value
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<Moveable>>();
+  test<std::deque<int>, std::vector<Moveable>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<Moveable>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<Moveable, min_allocator<Moveable>>>();
+
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    auto p = m.try_emplace(ConvertibleTransparent<int>{3}, 3);
+    assert(!p.second);
+    assert(transparent_used);
+  }
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    auto p = m.try_emplace(m.begin(), ConvertibleTransparent<int>{3}, 3);
+    assert(p->second == 3);
+    assert(transparent_used);
+  }
+  {
+    auto try_emplace = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      m.try_emplace(ConvertibleTransparent<Key>{key_arg}, value_arg);
+    };
+    test_emplace_exception_guarantee(try_emplace);
+  }
+
+  {
+    auto try_emplace_iter = [](auto& m, auto key_arg, auto value_arg) {
+      using M   = std::decay_t<decltype(m)>;
+      using Key = typename M::key_type;
+      m.try_emplace(m.begin(), ConvertibleTransparent<Key>{key_arg}, value_arg);
+    };
+    test_emplace_exception_guarantee(try_emplace_iter);
+  }
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.observers/comp.pass.cpp

@@ -0,0 +1,96 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// key_compare key_comp() const;
+// value_compare value_comp() const;
+
+#include <cassert>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+
+#include "test_macros.h"
+
+int main(int, char**) {
+  {
+    using M    = std::flat_map<int, char>;
+    using Comp = std::less<int>; // the default
+    M m        = {};
+    ASSERT_SAME_TYPE(M::key_compare, Comp);
+    static_assert(!std::is_same_v<M::value_compare, Comp>);
+    ASSERT_SAME_TYPE(decltype(m.key_comp()), Comp);
+    ASSERT_SAME_TYPE(decltype(m.value_comp()), M::value_compare);
+    Comp kc = m.key_comp();
+    assert(kc(1, 2));
+    assert(!kc(2, 1));
+    auto vc = m.value_comp();
+    ASSERT_SAME_TYPE(decltype(vc(std::make_pair(1, 2), std::make_pair(1, 2))), bool);
+    assert(vc({1, '2'}, {2, '1'}));
+    assert(!vc({2, '1'}, {1, '2'}));
+  }
+  {
+    using Comp = std::function<bool(int, int)>;
+    using M    = std::flat_map<int, int, Comp>;
+    Comp comp  = std::greater<int>();
+    M m({}, comp);
+    ASSERT_SAME_TYPE(M::key_compare, Comp);
+    ASSERT_SAME_TYPE(decltype(m.key_comp()), Comp);
+    ASSERT_SAME_TYPE(decltype(m.value_comp()), M::value_compare);
+    Comp kc = m.key_comp();
+    assert(!kc(1, 2));
+    assert(kc(2, 1));
+    auto vc = m.value_comp();
+    auto a  = std::make_pair(1, 2);
+    ASSERT_SAME_TYPE(decltype(vc(a, a)), bool);
+    static_assert(!noexcept(vc(a, a)));
+    assert(!vc({1, 2}, {2, 1}));
+    assert(vc({2, 1}, {1, 2}));
+  }
+  {
+    using Comp = std::less<>;
+    using M    = std::flat_map<int, int, Comp>;
+    M m        = {};
+    ASSERT_SAME_TYPE(M::key_compare, Comp);
+    ASSERT_SAME_TYPE(decltype(m.key_comp()), Comp);
+    ASSERT_SAME_TYPE(decltype(m.value_comp()), M::value_compare);
+    Comp kc = m.key_comp();
+    assert(kc(1, 2));
+    assert(!kc(2, 1));
+    auto vc = m.value_comp();
+    auto a  = std::make_pair(1, 2);
+    ASSERT_SAME_TYPE(decltype(vc(a, a)), bool);
+    assert(vc({1, 2}, {2, 1}));
+    assert(!vc({2, 1}, {1, 2}));
+  }
+  {
+    using Comp = std::function<bool(const std::vector<int>&, const std::vector<int>&)>;
+    using M    = std::flat_map<std::vector<int>, int, Comp>;
+    Comp comp  = [i = 1](const auto& x, const auto& y) { return x[i] < y[i]; };
+    M m({}, comp);
+    auto vc = m.value_comp();
+    static_assert(sizeof(vc) >= sizeof(Comp));
+    comp = nullptr;
+    m    = M({}, nullptr);
+    assert(m.key_comp() == nullptr);
+    // At this point, m.key_comp() is disengaged.
+    // But the std::function captured by copy inside `vc` remains valid.
+    auto a = std::make_pair(std::vector<int>{2, 1, 4}, 42);
+    auto b = std::make_pair(std::vector<int>{1, 2, 3}, 42);
+    auto c = std::make_pair(std::vector<int>{0, 3, 2}, 42);
+    assert(vc(a, b));
+    assert(vc(b, c));
+    assert(!vc(b, a));
+    assert(!vc(c, b));
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.observers/keys_values.pass.cpp

@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// const key_container_type& keys() const noexcept
+// const mapped_container_type& values() const noexcept
+
+#include <algorithm>
+#include <cassert>
+#include <flat_map>
+#include <functional>
+#include <utility>
+#include <vector>
+#include <deque>
+#include <string>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, std::less<Key>, KeyContainer, ValueContainer>;
+
+  const M m                                                 = {{4, 'a'}, {2, 'b'}, {3, 'c'}};
+  std::same_as<const KeyContainer&> decltype(auto) keys     = m.keys();
+  std::same_as<const ValueContainer&> decltype(auto) values = m.values();
+
+  // noexcept
+  static_assert(noexcept(m.keys()));
+  static_assert(noexcept(m.values()));
+
+  auto expected_keys   = {2, 3, 4};
+  auto expected_values = {'b', 'c', 'a'};
+  assert(std::ranges::equal(keys, expected_keys));
+  assert(std::ranges::equal(values, expected_values));
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<char>>();
+  test<std::deque<int>, std::vector<char>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<char>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<char, min_allocator<char>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/contains.pass.cpp

@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// bool contains(const key_type& x) const;
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <utility>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  {
+    using M = std::flat_map<Key, Value, std::less<>, KeyContainer, ValueContainer>;
+    M m     = {{1, 1}, {2, 2}, {4, 4}, {5, 5}, {8, 8}};
+    assert(!m.contains(0));
+    assert(m.contains(1));
+    assert(m.contains(2));
+    assert(!m.contains(3));
+    assert(m.contains(4));
+    assert(m.contains(5));
+    assert(!m.contains(6));
+    assert(!m.contains(7));
+    assert(std::as_const(m).contains(8));
+    assert(!std::as_const(m).contains(9));
+    m.clear();
+    assert(!m.contains(1));
+  }
+  {
+    using M = std::flat_map<Key, Value, std::greater<int>, KeyContainer, ValueContainer>;
+    M m     = {{1, 0}, {2, 0}, {4, 0}, {5, 0}, {8, 0}};
+    assert(!m.contains(0));
+    assert(m.contains(1));
+    assert(m.contains(2));
+    assert(!m.contains(3));
+    assert(m.contains(4));
+    assert(m.contains(5));
+    assert(!m.contains(6));
+    assert(!m.contains(7));
+    assert(std::as_const(m).contains(8));
+    assert(!std::as_const(m).contains(9));
+    m.clear();
+    assert(!m.contains(1));
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<int>>();
+  test<std::deque<int>, std::vector<int>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<int>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>();
+
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/contains_transparent.pass.cpp

@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// template<class K> bool contains(const K& x) const;
+
+#include <cassert>
+#include <flat_map>
+#include <string>
+#include <utility>
+#include <deque>
+
+#include "MinSequenceContainer.h"
+#include "../helpers.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+// Constraints: The qualified-id Compare::is_transparent is valid and denotes a type.
+template <class M>
+concept CanContains     = requires(M m, Transparent<int> k) { m.contains(k); };
+using TransparentMap    = std::flat_map<int, double, TransparentComparator>;
+using NonTransparentMap = std::flat_map<int, double, NonTransparentComparator>;
+static_assert(CanContains<TransparentMap>);
+static_assert(CanContains<const TransparentMap>);
+static_assert(!CanContains<NonTransparentMap>);
+static_assert(!CanContains<const NonTransparentMap>);
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+  using M     = std::flat_map<Key, Value, TransparentComparator, KeyContainer, ValueContainer>;
+
+  M m = {{"alpha", 1}, {"beta", 2}, {"epsilon", 3}, {"eta", 4}, {"gamma", 5}};
+  ASSERT_SAME_TYPE(decltype(m.contains(Transparent<std::string>{"abc"})), bool);
+  ASSERT_SAME_TYPE(decltype(std::as_const(m).contains(Transparent<std::string>{"b"})), bool);
+  assert(m.contains(Transparent<std::string>{"alpha"}) == true);
+  assert(m.contains(Transparent<std::string>{"beta"}) == true);
+  assert(m.contains(Transparent<std::string>{"epsilon"}) == true);
+  assert(m.contains(Transparent<std::string>{"eta"}) == true);
+  assert(m.contains(Transparent<std::string>{"gamma"}) == true);
+  assert(m.contains(Transparent<std::string>{"al"}) == false);
+  assert(m.contains(Transparent<std::string>{""}) == false);
+  assert(m.contains(Transparent<std::string>{"g"}) == false);
+}
+
+int main(int, char**) {
+  test<std::vector<std::string>, std::vector<int>>();
+  test<std::deque<std::string>, std::vector<int>>();
+  test<MinSequenceContainer<std::string>, MinSequenceContainer<int>>();
+  test<std::vector<std::string, min_allocator<std::string>>, std::vector<int, min_allocator<int>>>();
+
+  {
+    bool transparent_used = false;
+    TransparentComparator c(transparent_used);
+    std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
+    assert(!transparent_used);
+    auto b = m.contains(Transparent<int>{3});
+    assert(b);
+    assert(transparent_used);
+  }
+  return 0;
+}

libcxx/test/std/containers/container.adaptors/flat.map/flat.map.operations/count.pass.cpp

@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// <flat_map>
+
+// size_type count(const key_type& x) const;
+
+#include <cassert>
+#include <deque>
+#include <flat_map>
+#include <functional>
+#include <utility>
+
+#include "MinSequenceContainer.h"
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class KeyContainer, class ValueContainer>
+void test() {
+  using Key   = typename KeyContainer::value_type;
+  using Value = typename ValueContainer::value_type;
+
+  {
+    using M = std::flat_map<Key, Value, std::less<>, KeyContainer, ValueContainer>;
+    M m     = {{1, 1}, {2, 2}, {4, 4}, {5, 5}, {8, 8}};
+    ASSERT_SAME_TYPE(decltype(m.count(0)), size_t);
+    assert(m.count(0) == 0);
+    assert(m.count(1) == 1);
+    assert(m.count(2) == 1);
+    assert(m.count(3) == 0);
+    assert(m.count(4) == 1);
+    assert(m.count(5) == 1);
+    assert(m.count(6) == 0);
+    assert(m.count(7) == 0);
+    assert(std::as_const(m).count(8) == 1);
+    assert(std::as_const(m).count(9) == 0);
+  }
+  {
+    using M = std::flat_map<Key, Value, std::greater<int>, KeyContainer, ValueContainer>;
+    M m     = {{1, 0}, {2, 0}, {4, 0}, {5, 0}, {8, 0}};
+    ASSERT_SAME_TYPE(decltype(m.count(0)), size_t);
+    assert(m.count(0) == 0);
+    assert(m.count(1) == 1);
+    assert(m.count(2) == 1);
+    assert(m.count(3) == 0);
+    assert(m.count(4) == 1);
+    assert(m.count(5) == 1);
+    assert(m.count(6) == 0);
+    assert(m.count(7) == 0);
+    assert(std::as_const(m).count(8) == 1);
+    assert(std::as_const(m).count(9) == 0);
+  }
+}
+
+int main(int, char**) {
+  test<std::vector<int>, std::vector<int>>();
+  test<std::deque<int>, std::vector<int>>();
+  test<MinSequenceContainer<int>, MinSequenceContainer<int>>();
+  test<std::vector<int, min_allocator<int>>, std::vector<int, min_allocator<int>>>();
+
+  return 0;
+}