[libcxx][ranges] revert join_view::iterator and sentinel to be in-class

(cherry picked from commit 3b059cd25b8ce31762b76a3b172fdd811c07dc34)

3 files changed, 67 insertions, 51 deletions

diff --git a/libcxx/include/__ranges/join_view.h b/libcxx/include/__ranges/join_view.h
index 9d56e13b8439..7c078422e900 100644
--- a/libcxx/include/__ranges/join_view.h
+++ b/libcxx/include/__ranges/join_view.h
@@ -69,14 +69,6 @@ namespace ranges {
     >;
   };
 
-  template <input_range _View, bool _Const>
-    requires view<_View> && input_range<range_reference_t<_View>>
-  struct __join_view_iterator;
-
-  template <input_range _View, bool _Const>
-    requires view<_View> && input_range<range_reference_t<_View>>
-  struct __join_view_sentinel;
-
   template<input_range _View>
     requires view<_View> && input_range<range_reference_t<_View>>
   class join_view
@@ -84,19 +76,9 @@ namespace ranges {
   private:
     using _InnerRange = range_reference_t<_View>;
 
-    template<bool _Const>
-    using __iterator = __join_view_iterator<_View, _Const>;
-
-    template<bool _Const>
-    using __sentinel = __join_view_sentinel<_View, _Const>;
+    template<bool> struct __iterator;
 
-    template <input_range _View2, bool _Const2>
-      requires view<_View2> && input_range<range_reference_t<_View2>>
-    friend struct __join_view_iterator;
-
-    template <input_range _View2, bool _Const2>
-      requires view<_View2> && input_range<range_reference_t<_View2>>
-    friend struct __join_view_sentinel;
+    template<bool> struct __sentinel;
 
     template <class>
     friend struct std::__segmented_iterator_traits;
@@ -167,12 +149,12 @@ namespace ranges {
     }
   };
 
-  template<input_range _View, bool _Const>
+  template<input_range _View>
     requires view<_View> && input_range<range_reference_t<_View>>
-  struct __join_view_sentinel {
-    template<input_range _View2, bool>
-      requires view<_View2> && input_range<range_reference_t<_View2>>
-    friend struct __join_view_sentinel;
+  template<bool _Const>
+  struct join_view<_View>::__sentinel {
+  template<bool>
+    friend struct __sentinel;
 
   private:
     using _Parent = __maybe_const<_Const, join_view<_View>>;
@@ -181,37 +163,42 @@ namespace ranges {
 
   public:
     _LIBCPP_HIDE_FROM_ABI
-    __join_view_sentinel() = default;
+    __sentinel() = default;
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr explicit __join_view_sentinel(_Parent& __parent)
+    constexpr explicit __sentinel(_Parent& __parent)
       : __end_(ranges::end(__parent.__base_)) {}
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr __join_view_sentinel(__join_view_sentinel<_View, !_Const> __s)
+    constexpr __sentinel(__sentinel<!_Const> __s)
       requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
       : __end_(std::move(__s.__end_)) {}
 
     template<bool _OtherConst>
       requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
     _LIBCPP_HIDE_FROM_ABI
-    friend constexpr bool operator==(const __join_view_iterator<_View, _OtherConst>& __x, const __join_view_sentinel& __y) {
+    friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
       return __x.__outer_ == __y.__end_;
     }
   };
 
-  template<input_range _View, bool _Const>
+  // https://reviews.llvm.org/D142811#inline-1383022
+  // To simplify the segmented iterator traits specialization,
+  // make the iterator `final`
+  template<input_range _View>
     requires view<_View> && input_range<range_reference_t<_View>>
-  struct __join_view_iterator
+  template<bool _Const>
+  struct join_view<_View>::__iterator final
     : public __join_view_iterator_category<__maybe_const<_Const, _View>> {
 
-    template<input_range _View2, bool>
-      requires view<_View2> && input_range<range_reference_t<_View2>>
-    friend struct __join_view_iterator;
+    template<bool>
+    friend struct __iterator;
 
     template <class>
     friend struct std::__segmented_iterator_traits;
 
+    static constexpr bool __is_join_view_iterator = true;
+
   private:
     using _Parent = __maybe_const<_Const, join_view<_View>>;
     using _Base = __maybe_const<_Const, _View>;
@@ -246,7 +233,7 @@ namespace ranges {
         __inner_.reset();
     }
 
-    _LIBCPP_HIDE_FROM_ABI constexpr __join_view_iterator(_Parent* __parent, _Outer __outer, _Inner __inner)
+    _LIBCPP_HIDE_FROM_ABI constexpr __iterator(_Parent* __parent, _Outer __outer, _Inner __inner)
       : __outer_(std::move(__outer)), __inner_(std::move(__inner)), __parent_(__parent) {}
 
   public:
@@ -267,17 +254,17 @@ namespace ranges {
       range_difference_t<_Base>, range_difference_t<range_reference_t<_Base>>>;
 
     _LIBCPP_HIDE_FROM_ABI
-    __join_view_iterator() requires default_initializable<_Outer> = default;
+    __iterator() requires default_initializable<_Outer> = default;
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr __join_view_iterator(_Parent& __parent, _Outer __outer)
+    constexpr __iterator(_Parent& __parent, _Outer __outer)
       : __outer_(std::move(__outer))
       , __parent_(std::addressof(__parent)) {
       __satisfy();
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr __join_view_iterator(__join_view_iterator<_View, !_Const> __i)
+    constexpr __iterator(__iterator<!_Const> __i)
       requires _Const &&
                convertible_to<iterator_t<_View>, _Outer> &&
                convertible_to<iterator_t<_InnerRange>, _Inner>
@@ -298,7 +285,7 @@ namespace ranges {
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr __join_view_iterator& operator++() {
+    constexpr __iterator& operator++() {
       auto&& __inner = [&]() -> auto&& {
         if constexpr (__ref_is_glvalue)
           return *__outer_;
@@ -318,7 +305,7 @@ namespace ranges {
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr __join_view_iterator operator++(int)
+    constexpr __iterator operator++(int)
       requires __ref_is_glvalue &&
                forward_range<_Base> &&
                forward_range<range_reference_t<_Base>>
@@ -329,7 +316,7 @@ namespace ranges {
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr __join_view_iterator& operator--()
+    constexpr __iterator& operator--()
       requires __ref_is_glvalue &&
                bidirectional_range<_Base> &&
                bidirectional_range<range_reference_t<_Base>> &&
@@ -348,7 +335,7 @@ namespace ranges {
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    constexpr __join_view_iterator operator--(int)
+    constexpr __iterator operator--(int)
       requires __ref_is_glvalue &&
                bidirectional_range<_Base> &&
                bidirectional_range<range_reference_t<_Base>> &&
@@ -360,7 +347,7 @@ namespace ranges {
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    friend constexpr bool operator==(const __join_view_iterator& __x, const __join_view_iterator& __y)
+    friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
       requires __ref_is_glvalue &&
                equality_comparable<iterator_t<_Base>> &&
                equality_comparable<iterator_t<range_reference_t<_Base>>>
@@ -369,14 +356,14 @@ namespace ranges {
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    friend constexpr decltype(auto) iter_move(const __join_view_iterator& __i)
+    friend constexpr decltype(auto) iter_move(const __iterator& __i)
       noexcept(noexcept(ranges::iter_move(*__i.__inner_)))
     {
       return ranges::iter_move(*__i.__inner_);
     }
 
     _LIBCPP_HIDE_FROM_ABI
-    friend constexpr void iter_swap(const __join_view_iterator& __x, const __join_view_iterator& __y)
+    friend constexpr void iter_swap(const __iterator& __x, const __iterator& __y)
       noexcept(noexcept(ranges::iter_swap(*__x.__inner_, *__y.__inner_)))
       requires indirectly_swappable<_Inner>
     {
@@ -404,12 +391,12 @@ inline namespace __cpo {
 } // namespace views
 } // namespace ranges
 
-template <class _View, bool _Const>
-  requires(ranges::common_range<typename ranges::__join_view_iterator<_View, _Const>::_Parent> &&
-           __is_cpp17_random_access_iterator<typename ranges::__join_view_iterator<_View, _Const>::_Outer>::value &&
-           __is_cpp17_random_access_iterator<typename ranges::__join_view_iterator<_View, _Const>::_Inner>::value)
-struct __segmented_iterator_traits<ranges::__join_view_iterator<_View, _Const>> {
-  using _JoinViewIterator = ranges::__join_view_iterator<_View, _Const>;
+template <class _JoinViewIterator>
+  requires(_JoinViewIterator::__is_join_view_iterator &&
+           ranges::common_range<typename _JoinViewIterator::_Parent> &&
+           __is_cpp17_random_access_iterator<typename _JoinViewIterator::_Outer>::value &&
+           __is_cpp17_random_access_iterator<typename _JoinViewIterator::_Inner>::value)
+struct __segmented_iterator_traits<_JoinViewIterator> {
 
   using __segment_iterator =
       _LIBCPP_NODEBUG __iterator_with_data<typename _JoinViewIterator::_Outer, typename _JoinViewIterator::_Parent*>;
diff --git a/libcxx/test/libcxx/containers/sequences/deque/segmented_iterator.compile.pass.cpp b/libcxx/test/libcxx/containers/sequences/deque/segmented_iterator.compile.pass.cpp
new file mode 100644
index 000000000000..27100f9b45e3
--- /dev/null
+++ b/libcxx/test/libcxx/containers/sequences/deque/segmented_iterator.compile.pass.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <deque>
+
+
+using DequeIterator = typename std::deque<int>::iterator;
+static_assert(std::__is_segmented_iterator<DequeIterator>::value, "");
diff --git a/libcxx/test/libcxx/ranges/range.adaptors/range.join/segmented_iterator.compile.pass.cpp b/libcxx/test/libcxx/ranges/range.adaptors/range.join/segmented_iterator.compile.pass.cpp
new file mode 100644
index 000000000000..08b8949eeb18
--- /dev/null
+++ b/libcxx/test/libcxx/ranges/range.adaptors/range.join/segmented_iterator.compile.pass.cpp
@@ -0,0 +1,16 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+#include <ranges>
+#include <vector>
+
+using JoinView = decltype(std::views::join(std::declval<std::vector<std::vector<int>>&>()));
+using JoinIter = std::ranges::iterator_t<JoinView>;
+static_assert(std::__is_segmented_iterator<JoinIter>::value);