--- a/libcxx/include/concepts	Mon May 25 11:55:54 2020 +0900
+++ b/libcxx/include/concepts	Tue Jun 08 06:07:14 2021 +0900
@@ -67,9 +67,9 @@
   template<class T, class... Args>
     concept constructible_from = see below;
 
-  // [concept.defaultconstructible], concept default_constructible
+  // [concept.default.init], concept default_initializable
   template<class T>
-    concept default_constructible = see below;
+    concept default_initializable = see below;
 
   // [concept.moveconstructible], concept move_constructible
   template<class T>
@@ -79,11 +79,6 @@
   template<class T>
     concept copy_constructible = see below;
 
-  // [concepts.compare], comparison concepts
-  // [concept.boolean], concept boolean
-  template<class B>
-    concept boolean = see below;
-
   // [concept.equalitycomparable], concept equality_comparable
   template<class T>
     concept equality_comparable = see below;
@@ -135,7 +130,9 @@
 */
 
 #include <__config>
+#include <__functional_base>
 #include <type_traits>
+#include <utility>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -147,7 +144,7 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if _LIBCPP_STD_VER > 17 && defined(__cpp_concepts) && __cpp_concepts >= 201811L
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 // [concept.same]
 
@@ -157,7 +154,298 @@
 template<class _Tp, class _Up>
 concept same_as = __same_as_impl<_Tp, _Up> && __same_as_impl<_Up, _Tp>;
 
-#endif //_LIBCPP_STD_VER > 17 && defined(__cpp_concepts) && __cpp_concepts >= 201811L
+// [concept.derived]
+template<class _Dp, class _Bp>
+concept derived_from =
+  is_base_of_v<_Bp, _Dp> &&
+  is_convertible_v<const volatile _Dp*, const volatile _Bp*>;
+
+// [concept.convertible]
+template<class _From, class _To>
+concept convertible_to =
+  is_convertible_v<_From, _To> &&
+  requires(add_rvalue_reference_t<_From> (&__f)()) {
+    static_cast<_To>(__f());
+  };
+
+// [concept.commonref]
+template<class _Tp, class _Up>
+concept common_reference_with =
+  same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>> &&
+  convertible_to<_Tp, common_reference_t<_Tp, _Up>> &&
+  convertible_to<_Up, common_reference_t<_Tp, _Up>>;
+
+// [concept.common]
+template<class _Tp, class _Up>
+concept common_with =
+  same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>> &&
+  requires {
+    static_cast<common_type_t<_Tp, _Up>>(declval<_Tp>());
+    static_cast<common_type_t<_Tp, _Up>>(declval<_Up>());
+  } &&
+  common_reference_with<
+    add_lvalue_reference_t<const _Tp>,
+    add_lvalue_reference_t<const _Up>> &&
+  common_reference_with<
+    add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
+    common_reference_t<
+      add_lvalue_reference_t<const _Tp>,
+      add_lvalue_reference_t<const _Up>>>;
+
+// [concepts.arithmetic], arithmetic concepts
+template<class _Tp>
+concept integral = is_integral_v<_Tp>;
+
+template<class _Tp>
+concept signed_integral = integral<_Tp> && is_signed_v<_Tp>;
+
+template<class _Tp>
+concept unsigned_integral = integral<_Tp> && !signed_integral<_Tp>;
+
+template<class _Tp>
+concept floating_point = is_floating_point_v<_Tp>;
+
+// [concept.assignable]
+template<class _Lhs, class _Rhs>
+concept assignable_from =
+  is_lvalue_reference_v<_Lhs> &&
+  common_reference_with<__make_const_lvalue_ref<_Lhs>, __make_const_lvalue_ref<_Rhs>> &&
+  requires (_Lhs __lhs, _Rhs&& __rhs) {
+    { __lhs = _VSTD::forward<_Rhs>(__rhs) } -> same_as<_Lhs>;
+  };
+
+// [concept.destructible]
+
+template<class _Tp>
+concept destructible = is_nothrow_destructible_v<_Tp>;
+
+// [concept.constructible]
+template<class _Tp, class... _Args>
+concept constructible_from =
+    destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
+
+// [concept.default.init]
+
+template<class _Tp>
+concept __default_initializable = requires { ::new _Tp; };
+
+template<class _Tp>
+concept default_initializable = constructible_from<_Tp> &&
+    requires { _Tp{}; } && __default_initializable<_Tp>;
+
+// [concept.moveconstructible]
+template<class _Tp>
+concept move_constructible =
+  constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
+
+// [concept.copyconstructible]
+template<class _Tp>
+concept copy_constructible =
+  move_constructible<_Tp> &&
+  constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp> &&
+  constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp> &&
+  constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
+
+// Whether a type is a class type or enumeration type according to the Core wording.
+template<class _Tp>
+concept __class_or_enum = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
+
+// [concept.swappable]
+namespace ranges::__swap {
+  // Deleted to inhibit ADL
+  template<class _Tp>
+  void swap(_Tp&, _Tp&) = delete;
+
+
+  // [1]
+  template<class _Tp, class _Up>
+  concept __unqualified_swappable_with =
+    (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
+    requires(_Tp&& __t, _Up&& __u) {
+      swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+    };
+
+  struct __fn;
+
+  template<class _Tp, class _Up, size_t _Size>
+  concept __swappable_arrays =
+    !__unqualified_swappable_with<_Tp(&)[_Size], _Up(&)[_Size]> &&
+    extent_v<_Tp> == extent_v<_Up> &&
+    requires(_Tp(& __t)[_Size], _Up(& __u)[_Size], const __fn& __swap) {
+      __swap(__t[0], __u[0]);
+    };
+
+  template<class _Tp>
+  concept __exchangeable =
+    !__unqualified_swappable_with<_Tp&, _Tp&> &&
+    move_constructible<_Tp> &&
+    assignable_from<_Tp&, _Tp>;
+
+  struct __fn {
+    // 2.1   `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
+    // *The name `swap` is used here unqualified.
+    template<class _Tp, class _Up>
+    requires __unqualified_swappable_with<_Tp, _Up>
+    constexpr void operator()(_Tp&& __t, _Up&& __u) const
+    noexcept(noexcept(swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+    {
+      swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+    }
+
+    // 2.2   Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
+    template<class _Tp, class _Up, size_t _Size>
+    requires __swappable_arrays<_Tp, _Up, _Size>
+    constexpr void operator()(_Tp(& __t)[_Size], _Up(& __u)[_Size]) const
+    noexcept(noexcept((*this)(*__t, *__u)))
+    {
+      // TODO(cjdb): replace with `ranges::swap_ranges`.
+      for (size_t __i = 0; __i < _Size; ++__i) {
+        (*this)(__t[__i], __u[__i]);
+      }
+    }
+
+    // 2.3   Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
+    template<__exchangeable _Tp>
+    constexpr void operator()(_Tp& __x, _Tp& __y) const
+    noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>)
+    {
+      __y = _VSTD::exchange(__x, _VSTD::move(__y));
+    }
+  };
+} // namespace ranges::__swap
+
+namespace ranges::inline __cpo {
+  inline constexpr auto swap = __swap::__fn{};
+} // namespace ranges::__cpo
+
+template<class _Tp>
+concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
+
+template<class _Tp, class _Up>
+concept swappable_with =
+  common_reference_with<_Tp, _Up> &&
+  requires(_Tp&& __t, _Up&& __u) {
+    ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Tp>(__t));
+    ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Up>(__u));
+    ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
+    ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Tp>(__t));
+  };
+
+// [concept.booleantestable]
+template<class _Tp>
+concept __boolean_testable_impl = convertible_to<_Tp, bool>;
+
+template<class _Tp>
+concept __boolean_testable = __boolean_testable_impl<_Tp> && requires(_Tp&& __t) {
+  { !std::forward<_Tp>(__t) } -> __boolean_testable_impl;
+};
+
+// [concept.equalitycomparable]
+template<class _Tp, class _Up>
+concept __weakly_equality_comparable_with =
+  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
+    { __t == __u } -> __boolean_testable;
+    { __t != __u } -> __boolean_testable;
+    { __u == __t } -> __boolean_testable;
+    { __u != __t } -> __boolean_testable;
+  };
+
+template<class _Tp>
+concept equality_comparable = __weakly_equality_comparable_with<_Tp, _Tp>;
+
+template<class _Tp, class _Up>
+concept equality_comparable_with =
+  equality_comparable<_Tp> && equality_comparable<_Up> &&
+  common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>> &&
+  equality_comparable<
+    common_reference_t<
+      __make_const_lvalue_ref<_Tp>,
+      __make_const_lvalue_ref<_Up>>> &&
+  __weakly_equality_comparable_with<_Tp, _Up>;
+
+// [concept.totallyordered]
+
+template<class _Tp, class _Up>
+concept __partially_ordered_with =
+  requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
+    { __t <  __u } -> __boolean_testable;
+    { __t >  __u } -> __boolean_testable;
+    { __t <= __u } -> __boolean_testable;
+    { __t >= __u } -> __boolean_testable;
+    { __u <  __t } -> __boolean_testable;
+    { __u >  __t } -> __boolean_testable;
+    { __u <= __t } -> __boolean_testable;
+    { __u >= __t } -> __boolean_testable;
+  };
+
+template<class _Tp>
+concept totally_ordered = equality_comparable<_Tp> && __partially_ordered_with<_Tp, _Tp>;
+
+template<class _Tp, class _Up>
+concept totally_ordered_with =
+  totally_ordered<_Tp> && totally_ordered<_Up> &&
+  equality_comparable_with<_Tp, _Up> &&
+  totally_ordered<
+    common_reference_t<
+      __make_const_lvalue_ref<_Tp>,
+      __make_const_lvalue_ref<_Up>>> &&
+  __partially_ordered_with<_Tp, _Up>;
+
+// [concepts.object]
+template<class _Tp>
+concept movable =
+  is_object_v<_Tp> &&
+  move_constructible<_Tp> &&
+  assignable_from<_Tp&, _Tp> &&
+  swappable<_Tp>;
+
+template<class _Tp>
+concept copyable =
+  copy_constructible<_Tp> &&
+  movable<_Tp> &&
+  assignable_from<_Tp&, _Tp&> &&
+  assignable_from<_Tp&, const _Tp&> &&
+  assignable_from<_Tp&, const _Tp>;
+
+template<class _Tp>
+concept semiregular = copyable<_Tp> && default_initializable<_Tp>;
+
+template<class _Tp>
+concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
+
+// [concept.invocable]
+template<class _Fn, class... _Args>
+concept invocable = requires(_Fn&& __fn, _Args&&... __args) {
+  _VSTD::invoke(_VSTD::forward<_Fn>(__fn), _VSTD::forward<_Args>(__args)...); // not required to be equality preserving
+};
+
+// [concept.regular.invocable]
+template<class _Fn, class... _Args>
+concept regular_invocable = invocable<_Fn, _Args...>;
+
+// [concept.predicate]
+template<class _Fn, class... _Args>
+concept predicate =
+  regular_invocable<_Fn, _Args...> && __boolean_testable<invoke_result_t<_Fn, _Args...>>;
+
+// [concept.relation]
+template<class _Rp, class _Tp, class _Up>
+concept relation =
+  predicate<_Rp, _Tp, _Tp> && predicate<_Rp, _Up, _Up> &&
+  predicate<_Rp, _Tp, _Up> && predicate<_Rp, _Up, _Tp>;
+
+// [concept.equiv]
+template<class _Rp, class _Tp, class _Up>
+concept equivalence_relation = relation<_Rp, _Tp, _Up>;
+
+// [concept.strictweakorder]
+template<class _Rp, class _Tp, class _Up>
+concept strict_weak_order = relation<_Rp, _Tp, _Up>;
+
+template<class _Tp, class _Up>
+concept __different_from = !same_as<remove_cvref_t<_Tp>, remove_cvref_t<_Up>>;
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
 
 _LIBCPP_END_NAMESPACE_STD