From 907ed12d950f8e138620769420e5f84c0c7ece78 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser@berlin.de>
Date: Fri, 22 Apr 2022 20:56:58 +0200
Subject: [PATCH] [libc++] Change vector<bool>::const_iterator::reference to
 bool in ABIv2

`vector<bool>::const_reference` and `vector<bool>::const_iterator::reference` should be the same type.

Reviewed By: Mordante, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D123851
---
 libcxx/docs/ReleaseNotes.rst                                   |  3 +++
 libcxx/include/__bit_reference                                 | 10 ++++++++--
 .../std/containers/sequences/vector.bool/iterators.pass.cpp    |  9 +++++++++
 .../test/std/containers/sequences/vector.bool/types.pass.cpp   |  4 ++++
 4 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
index dc86c588..ddb785b 100644
--- a/libcxx/docs/ReleaseNotes.rst
+++ b/libcxx/docs/ReleaseNotes.rst
@@ -86,6 +86,9 @@ API Changes
   supported anymore. Please migrate to using the new support for
   :ref:`assertions <assertions-mode>` instead.
 
+- ``vector<bool>::const_reference``, ``vector<bool>::const_iterator::reference``
+  and ``bitset::const_reference`` are now aliases for `bool` in the unstable ABI.
+
 ABI Changes
 -----------
 
diff --git a/libcxx/include/__bit_reference b/libcxx/include/__bit_reference
index 53af4b3..b6a4699 100644
--- a/libcxx/include/__bit_reference
+++ b/libcxx/include/__bit_reference
@@ -1109,7 +1109,11 @@ public:
     typedef typename _Cp::difference_type                                                          difference_type;
     typedef bool                                                                                  value_type;
     typedef __bit_iterator                                                                        pointer;
+#ifndef _LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL
     typedef typename conditional<_IsConst, __bit_const_reference<_Cp>, __bit_reference<_Cp> >::type reference;
+#else
+    using reference = typename conditional<_IsConst, bool, __bit_reference<_Cp>>::type;
+#endif
     typedef random_access_iterator_tag                                                            iterator_category;
 
 private:
@@ -1149,8 +1153,10 @@ public:
         return *this;
     }
 
-    _LIBCPP_INLINE_VISIBILITY reference operator*() const _NOEXCEPT
-        {return reference(__seg_, __storage_type(1) << __ctz_);}
+    _LIBCPP_INLINE_VISIBILITY reference operator*() const _NOEXCEPT {
+        return typename conditional<_IsConst, __bit_const_reference<_Cp>, __bit_reference<_Cp> >
+                ::type(__seg_, __storage_type(1) << __ctz_);
+    }
 
     _LIBCPP_INLINE_VISIBILITY __bit_iterator& operator++()
     {
diff --git a/libcxx/test/std/containers/sequences/vector.bool/iterators.pass.cpp b/libcxx/test/std/containers/sequences/vector.bool/iterators.pass.cpp
index 7714e53..1714c73 100644
--- a/libcxx/test/std/containers/sequences/vector.bool/iterators.pass.cpp
+++ b/libcxx/test/std/containers/sequences/vector.bool/iterators.pass.cpp
@@ -24,6 +24,15 @@
 
 int main(int, char**)
 {
+    using IterRefT = std::iterator_traits<std::vector<bool>::iterator>::reference;
+    ASSERT_SAME_TYPE(IterRefT, std::vector<bool>::reference);
+
+    using ConstIterRefT = std::iterator_traits<std::vector<bool>::const_iterator>::reference;
+#if !defined(_LIBCPP_VERSION) || defined(_LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL)
+    ASSERT_SAME_TYPE(ConstIterRefT, bool);
+#else
+    ASSERT_SAME_TYPE(ConstIterRefT, std::__bit_const_reference<std::vector<bool> >);
+#endif
     {
         typedef bool T;
         typedef std::vector<T> C;
diff --git a/libcxx/test/std/containers/sequences/vector.bool/types.pass.cpp b/libcxx/test/std/containers/sequences/vector.bool/types.pass.cpp
index 07053ee..d75d715 100644
--- a/libcxx/test/std/containers/sequences/vector.bool/types.pass.cpp
+++ b/libcxx/test/std/containers/sequences/vector.bool/types.pass.cpp
@@ -24,6 +24,7 @@
 //     typedef typename allocator_type::const_pointer   const_pointer;
 //     typedef std::reverse_iterator<iterator>          reverse_iterator;
 //     typedef std::reverse_iterator<const_iterator>    const_reverse_iterator;
+//     typedef bool                                     const_reference;
 // };
 
 #include <vector>
@@ -66,6 +67,9 @@ test()
     static_assert((std::is_same<
         typename C::const_reverse_iterator,
         std::reverse_iterator<typename C::const_iterator> >::value), "");
+#if !defined(_LIBCPP_VERSION) || defined(_LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL)
+    static_assert(std::is_same<typename C::const_reference, bool>::value, "");
+#endif
 }
 
 int main(int, char**)
-- 
2.7.4