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[libc++] LWG3672: common_iterator::operator->() should return by value (#87899)

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## Abstract

This pull request implements LWG3672: `common_iterator::operator->()`
should return by value. The current implementation specifies that this
function should return the underlying pointer by reference (`T*
const&`), but it would be more intuitive to return it by value (`T*`).

## Reference

- [Draft C++ Standard:
[common.iter.access]](https://eel.is/c++draft/common.iter.access)
- [LWG3672](https://cplusplus.github.io/LWG/issue3672)
This commit is contained in:
Xiaoyang Liu 2024-05-16 13:25:04 -04:00 committed by GitHub
parent bd6c358d01
commit f03430f5e3
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
3 changed files with 11 additions and 11 deletions
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2
libcxx/docs/Status/Cxx23Issues.csv
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@ -165,7 +165,7 @@
"`3659 <https://wg21.link/LWG3659>`__","Consider ``ATOMIC_FLAG_INIT`` undeprecation","July 2022","|Complete|","15.0"
"`3670 <https://wg21.link/LWG3670>`__","``Cpp17InputIterators`` don't have integer-class difference types","July 2022","","","|ranges|"
"`3671 <https://wg21.link/LWG3671>`__","``atomic_fetch_xor`` missing from ``stdatomic.h``","July 2022","",""
"`3672 <https://wg21.link/LWG3672>`__","``common_iterator::operator->()`` should return by value","July 2022","","","|ranges|"
"`3672 <https://wg21.link/LWG3672>`__","``common_iterator::operator->()`` should return by value","July 2022","|Complete|","19.0","|ranges|"
"`3683 <https://wg21.link/LWG3683>`__","``operator==`` for ``polymorphic_allocator`` cannot deduce template argument in common cases","July 2022","",""
"`3687 <https://wg21.link/LWG3687>`__","``expected<cv void, E>`` move constructor should move","July 2022","|Complete|","16.0"
"`3692 <https://wg21.link/LWG3692>`__","``zip_view::iterator``'s ``operator<=>`` is overconstrained","July 2022","","","|ranges| |spaceship|"

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2
libcxx/include/__iterator/common_iterator.h
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@ -124,7 +124,7 @@ public:
}
template <class _I2 = _Iter>
_LIBCPP_HIDE_FROM_ABI decltype(auto) operator->() const
_LIBCPP_HIDE_FROM_ABI 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>>)

14
libcxx/test/std/iterators/predef.iterators/iterators.common/arrow.pass.cpp
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@ -8,7 +8,7 @@
// UNSUPPORTED: c++03, c++11, c++14, c++17
// decltype(auto) operator->() const
// auto operator->() const
// requires see below;
#include <iterator>
@ -28,11 +28,11 @@ void test() {
using Common = std::common_iterator<Iterator, sentinel_wrapper<Iterator>>;
Common common(iter);
std::same_as<Iterator> auto result = common.operator->();
std::same_as<Iterator> decltype(auto) result = common.operator->();
assert(base(result) == buffer);
Common const ccommon(iter);
std::same_as<Iterator> auto cresult = ccommon.operator->();
std::same_as<Iterator> decltype(auto) cresult = ccommon.operator->();
assert(base(cresult) == buffer);
};
@ -48,11 +48,11 @@ void test() {
using Common = std::common_iterator<Iterator, sentinel_type<int*>>;
Common common(iter);
std::same_as<int*> auto result = common.operator->();
std::same_as<int*> decltype(auto) result = common.operator->();
assert(result == buffer);
Common const ccommon(iter);
std::same_as<int*> auto cresult = ccommon.operator->();
std::same_as<int*> decltype(auto) cresult = ccommon.operator->();
assert(cresult == buffer);
};
@ -73,13 +73,13 @@ void test() {
Common common(iter);
auto proxy = common.operator->();
std::same_as<int const*> auto result = proxy.operator->();
std::same_as<int const*> decltype(auto) result = proxy.operator->();
assert(result != buffer); // we copied to a temporary proxy
assert(*result == *buffer);
Common const ccommon(iter);
auto cproxy = ccommon.operator->();
std::same_as<int const*> auto cresult = cproxy.operator->();
std::same_as<int const*> decltype(auto) cresult = cproxy.operator->();
assert(cresult != buffer); // we copied to a temporary proxy
assert(*cresult == *buffer);
};