1 files changed, 299 insertions, 0 deletions
diff --git a/contrib/llvm-project/libcxx/include/__iterator/common_iterator.h b/contrib/llvm-project/libcxx/include/__iterator/common_iterator.h
new file mode 100644
index 000000000000..7b3f4610d531
--- /dev/null
+++ b/contrib/llvm-project/libcxx/include/__iterator/common_iterator.h
@@ -0,0 +1,299 @@
+// -*- 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___ITERATOR_COMMON_ITERATOR_H
+#define _LIBCPP___ITERATOR_COMMON_ITERATOR_H
+
+#include <__assert>
+#include <__concepts/assignable.h>
+#include <__concepts/constructible.h>
+#include <__concepts/convertible_to.h>
+#include <__concepts/copyable.h>
+#include <__concepts/derived_from.h>
+#include <__concepts/equality_comparable.h>
+#include <__concepts/same_as.h>
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iter_swap.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/readable_traits.h>
+#include <__memory/addressof.h>
+#include <__type_traits/is_pointer.h>
+#include <__utility/declval.h>
+#include <variant>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+template <class _Iter>
+concept __can_use_postfix_proxy =
+    constructible_from<iter_value_t<_Iter>, iter_reference_t<_Iter>> && move_constructible<iter_value_t<_Iter>>;
+
+template <input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent>
+  requires(!same_as<_Iter, _Sent> && copyable<_Iter>)
+class common_iterator {
+  struct __proxy {
+    _LIBCPP_HIDE_FROM_ABI constexpr const iter_value_t<_Iter>* operator->() const noexcept {
+      return std::addressof(__value_);
+    }
+    iter_value_t<_Iter> __value_;
+  };
+
+  struct __postfix_proxy {
+    _LIBCPP_HIDE_FROM_ABI constexpr const iter_value_t<_Iter>& operator*() const noexcept { return __value_; }
+    iter_value_t<_Iter> __value_;
+  };
+
+  variant<_Iter, _Sent> __hold_;
+  template <input_or_output_iterator _OtherIter, sentinel_for<_OtherIter> _OtherSent>
+    requires(!same_as<_OtherIter, _OtherSent> && copyable<_OtherIter>)
+  friend class common_iterator;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI common_iterator()
+    requires default_initializable<_Iter>
+  = default;
+
+  _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(_Iter __i) : __hold_(in_place_type<_Iter>, std::move(__i)) {}
+  _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(_Sent __s) : __hold_(in_place_type<_Sent>, std::move(__s)) {}
+
+  template <class _I2, class _S2>
+    requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent>
+  _LIBCPP_HIDE_FROM_ABI constexpr common_iterator(const common_iterator<_I2, _S2>& __other)
+      : __hold_([&]() -> variant<_Iter, _Sent> {
+          _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+              !__other.__hold_.valueless_by_exception(), "Attempted to construct from a valueless common_iterator");
+          if (__other.__hold_.index() == 0)
+            return variant<_Iter, _Sent>{in_place_index<0>, std::__unchecked_get<0>(__other.__hold_)};
+          return variant<_Iter, _Sent>{in_place_index<1>, std::__unchecked_get<1>(__other.__hold_)};
+        }()) {}
+
+  template <class _I2, class _S2>
+    requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> &&
+             assignable_from<_Iter&, const _I2&> && assignable_from<_Sent&, const _S2&>
+  _LIBCPP_HIDE_FROM_ABI common_iterator& operator=(const common_iterator<_I2, _S2>& __other) {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        !__other.__hold_.valueless_by_exception(), "Attempted to assign from a valueless common_iterator");
+
+    auto __idx       = __hold_.index();
+    auto __other_idx = __other.__hold_.index();
+
+    // If they're the same index, just assign.
+    if (__idx == 0 && __other_idx == 0)
+      std::__unchecked_get<0>(__hold_) = std::__unchecked_get<0>(__other.__hold_);
+    else if (__idx == 1 && __other_idx == 1)
+      std::__unchecked_get<1>(__hold_) = std::__unchecked_get<1>(__other.__hold_);
+
+    // Otherwise replace with the oposite element.
+    else if (__other_idx == 1)
+      __hold_.template emplace<1>(std::__unchecked_get<1>(__other.__hold_));
+    else if (__other_idx == 0)
+      __hold_.template emplace<0>(std::__unchecked_get<0>(__other.__hold_));
+
+    return *this;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator");
+    return *std::__unchecked_get<_Iter>(__hold_);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const
+    requires __dereferenceable<const _Iter>
+  {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator");
+    return *std::__unchecked_get<_Iter>(__hold_);
+  }
+
+  template <class _I2 = _Iter>
+  _LIBCPP_HIDE_FROM_ABI decltype(auto) operator->() const
+    requires indirectly_readable<const _I2> && (requires(const _I2& __i) {
+               __i.operator->();
+             } || is_reference_v<iter_reference_t<_I2>> || constructible_from<iter_value_t<_I2>, iter_reference_t<_I2>>)
+  {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_Iter>(__hold_), "Attempted to dereference a non-dereferenceable common_iterator");
+    if constexpr (is_pointer_v<_Iter> || requires(const _Iter& __i) { __i.operator->(); }) {
+      return std::__unchecked_get<_Iter>(__hold_);
+    } else if constexpr (is_reference_v<iter_reference_t<_Iter>>) {
+      auto&& __tmp = *std::__unchecked_get<_Iter>(__hold_);
+      return std::addressof(__tmp);
+    } else {
+      return __proxy{*std::__unchecked_get<_Iter>(__hold_)};
+    }
+  }
+
+  _LIBCPP_HIDE_FROM_ABI common_iterator& operator++() {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_Iter>(__hold_), "Attempted to increment a non-dereferenceable common_iterator");
+    ++std::__unchecked_get<_Iter>(__hold_);
+    return *this;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI decltype(auto) operator++(int) {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_Iter>(__hold_), "Attempted to increment a non-dereferenceable common_iterator");
+    if constexpr (forward_iterator<_Iter>) {
+      auto __tmp = *this;
+      ++*this;
+      return __tmp;
+    } else if constexpr (requires(_Iter& __i) {
+                           { *__i++ } -> __can_reference;
+                         } || !__can_use_postfix_proxy<_Iter>) {
+      return std::__unchecked_get<_Iter>(__hold_)++;
+    } else {
+      auto __p = __postfix_proxy{**this};
+      ++*this;
+      return __p;
+    }
+  }
+
+  template <class _I2, sentinel_for<_Iter> _S2>
+    requires sentinel_for<_Sent, _I2>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool
+  operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        !__x.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator");
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        !__y.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator");
+
+    auto __x_index = __x.__hold_.index();
+    auto __y_index = __y.__hold_.index();
+
+    if (__x_index == __y_index)
+      return true;
+
+    if (__x_index == 0)
+      return std::__unchecked_get<_Iter>(__x.__hold_) == std::__unchecked_get<_S2>(__y.__hold_);
+
+    return std::__unchecked_get<_Sent>(__x.__hold_) == std::__unchecked_get<_I2>(__y.__hold_);
+  }
+
+  template <class _I2, sentinel_for<_Iter> _S2>
+    requires sentinel_for<_Sent, _I2> && equality_comparable_with<_Iter, _I2>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool
+  operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        !__x.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator");
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        !__y.__hold_.valueless_by_exception(), "Attempted to compare a valueless common_iterator");
+
+    auto __x_index = __x.__hold_.index();
+    auto __y_index = __y.__hold_.index();
+
+    if (__x_index == 1 && __y_index == 1)
+      return true;
+
+    if (__x_index == 0 && __y_index == 0)
+      return std::__unchecked_get<_Iter>(__x.__hold_) == std::__unchecked_get<_I2>(__y.__hold_);
+
+    if (__x_index == 0)
+      return std::__unchecked_get<_Iter>(__x.__hold_) == std::__unchecked_get<_S2>(__y.__hold_);
+
+    return std::__unchecked_get<_Sent>(__x.__hold_) == std::__unchecked_get<_I2>(__y.__hold_);
+  }
+
+  template <sized_sentinel_for<_Iter> _I2, sized_sentinel_for<_Iter> _S2>
+    requires sized_sentinel_for<_Sent, _I2>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr iter_difference_t<_I2>
+  operator-(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        !__x.__hold_.valueless_by_exception(), "Attempted to subtract from a valueless common_iterator");
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        !__y.__hold_.valueless_by_exception(), "Attempted to subtract a valueless common_iterator");
+
+    auto __x_index = __x.__hold_.index();
+    auto __y_index = __y.__hold_.index();
+
+    if (__x_index == 1 && __y_index == 1)
+      return 0;
+
+    if (__x_index == 0 && __y_index == 0)
+      return std::__unchecked_get<_Iter>(__x.__hold_) - std::__unchecked_get<_I2>(__y.__hold_);
+
+    if (__x_index == 0)
+      return std::__unchecked_get<_Iter>(__x.__hold_) - std::__unchecked_get<_S2>(__y.__hold_);
+
+    return std::__unchecked_get<_Sent>(__x.__hold_) - std::__unchecked_get<_I2>(__y.__hold_);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter>
+  iter_move(const common_iterator& __i) noexcept(noexcept(ranges::iter_move(std::declval<const _Iter&>())))
+    requires input_iterator<_Iter>
+  {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_Iter>(__i.__hold_), "Attempted to iter_move a non-dereferenceable common_iterator");
+    return ranges::iter_move(std::__unchecked_get<_Iter>(__i.__hold_));
+  }
+
+  template <indirectly_swappable<_Iter> _I2, class _S2>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr void
+  iter_swap(const common_iterator& __x, const common_iterator<_I2, _S2>& __y) noexcept(
+      noexcept(ranges::iter_swap(std::declval<const _Iter&>(), std::declval<const _I2&>()))) {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_Iter>(__x.__hold_), "Attempted to iter_swap a non-dereferenceable common_iterator");
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        std::holds_alternative<_I2>(__y.__hold_), "Attempted to iter_swap a non-dereferenceable common_iterator");
+    return ranges::iter_swap(std::__unchecked_get<_Iter>(__x.__hold_), std::__unchecked_get<_I2>(__y.__hold_));
+  }
+};
+
+template <class _Iter, class _Sent>
+struct incrementable_traits<common_iterator<_Iter, _Sent>> {
+  using difference_type = iter_difference_t<_Iter>;
+};
+
+template <class _Iter>
+concept __denotes_forward_iter = requires {
+  typename iterator_traits<_Iter>::iterator_category;
+} && derived_from<typename iterator_traits<_Iter>::iterator_category, forward_iterator_tag>;
+
+template <class _Iter, class _Sent>
+concept __common_iter_has_ptr_op = requires(const common_iterator<_Iter, _Sent>& __a) { __a.operator->(); };
+
+template <class, class>
+struct __arrow_type_or_void {
+  using type = void;
+};
+
+template <class _Iter, class _Sent>
+  requires __common_iter_has_ptr_op<_Iter, _Sent>
+struct __arrow_type_or_void<_Iter, _Sent> {
+  using type = decltype(std::declval<const common_iterator<_Iter, _Sent>&>().operator->());
+};
+
+template <input_iterator _Iter, class _Sent>
+struct iterator_traits<common_iterator<_Iter, _Sent>> {
+  using iterator_concept  = _If<forward_iterator<_Iter>, forward_iterator_tag, input_iterator_tag>;
+  using iterator_category = _If<__denotes_forward_iter<_Iter>, forward_iterator_tag, input_iterator_tag>;
+  using pointer           = typename __arrow_type_or_void<_Iter, _Sent>::type;
+  using value_type        = iter_value_t<_Iter>;
+  using difference_type   = iter_difference_t<_Iter>;
+  using reference         = iter_reference_t<_Iter>;
+};
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ITERATOR_COMMON_ITERATOR_H