From 080a23bce12fa3f25860631f019777f728d2ef11 Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Fri, 2 Oct 2020 10:51:31 -0400
Subject: libstdc++: Add missing P0896 changes to <iterator>

I noticed that the following changes from this paper were not yet
implemented.

libstdc++-v3/ChangeLog:

	* include/bits/stl_iterator.h (reverse_iterator::iter_move):
	Define for C++20 as per P0896.
	(reverse_iterator::iter_swap): Likewise.
	(move_iterator::operator*): Apply P0896 changes for C++20.
	(move_iterator::operator[]): Likewise.
	* testsuite/24_iterators/reverse_iterator/cust.cc: New test.
---
 libstdc++-v3/include/bits/stl_iterator.h | 33 ++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

(limited to 'libstdc++-v3/include')

diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index f29bae9..2259f7c 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -362,6 +362,31 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       operator[](difference_type __n) const
       { return *(*this + __n); }
 
+#if __cplusplus > 201703L && __cpp_lib_concepts
+      friend constexpr iter_rvalue_reference_t<_Iterator>
+      iter_move(const reverse_iterator& __i)
+      noexcept(is_nothrow_copy_constructible_v<_Iterator>
+	       && noexcept(ranges::iter_move(--std::declval<_Iterator&>())))
+      {
+	auto __tmp = __i.base();
+	return ranges::iter_move(--__tmp);
+      }
+
+      template<indirectly_swappable<_Iterator> _Iter2>
+	friend constexpr void
+	iter_swap(const reverse_iterator& __x,
+		  const reverse_iterator<_Iter2>& __y)
+	noexcept(is_nothrow_copy_constructible_v<_Iterator>
+		 && is_nothrow_copy_constructible_v<_Iter2>
+		 && noexcept(ranges::iter_swap(--std::declval<_Iterator&>(),
+					       --std::declval<_Iter2&>())))
+	{
+	  auto __xtmp = __x.base();
+	  auto __ytmp = __y.base();
+	  ranges::iter_swap(--__xtmp, --__ytmp);
+	}
+#endif
+
     private:
       template<typename _Tp>
 	static _GLIBCXX17_CONSTEXPR _Tp*
@@ -1379,7 +1404,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       _GLIBCXX17_CONSTEXPR reference
       operator*() const
+#if __cplusplus > 201703L && __cpp_lib_concepts
+      { return ranges::iter_move(_M_current); }
+#else
       { return static_cast<reference>(*_M_current); }
+#endif
 
       _GLIBCXX17_CONSTEXPR pointer
       operator->() const
@@ -1445,7 +1474,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       _GLIBCXX17_CONSTEXPR reference
       operator[](difference_type __n) const
+#if __cplusplus > 201703L && __cpp_lib_concepts
+      { return ranges::iter_move(_M_current + __n); }
+#else
       { return std::move(_M_current[__n]); }
+#endif
 
 #if __cplusplus > 201703L && __cpp_lib_concepts
       template<sentinel_for<_Iterator> _Sent>
-- 
cgit v1.1