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[libc++][ranges] LWG3618: Unnecessary iter_move for transform_view::iterator (#91809)

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## Introduction

This patch implements LWG3618: Unnecessary `iter_move` for
`transform_view::iterator`.

`transform_view`'s iterator currently specifies a customization point
for `iter_move`. This customization point does the same thing that the
default implementation would do, but its sole purpose is to ensure the
appropriate conditional `noexcept` specification.

## Reference

-
[[range.transform.iterator]](https://eel.is/c++draft/range.transform.iterator)
- [LWG3618](https://cplusplus.github.io/LWG/issue3618)
This commit is contained in:
Xiaoyang Liu 2024-07-23 01:32:37 +09:00 committed by GitHub
parent ec966f699d
commit 3d7622ea0b
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4 changed files with 2 additions and 58 deletions
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2
libcxx/docs/Status/Cxx23Issues.csv
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@ -146,7 +146,7 @@
"`3610 <https://wg21.link/LWG3610>`__","``iota_view::size`` sometimes rejects integer-class types","February 2022","","","|ranges|"
"`3612 <https://wg21.link/LWG3612>`__","Inconsistent pointer alignment in ``std::format`` ","February 2022","|Complete|","14.0","|format|"
"`3616 <https://wg21.link/LWG3616>`__","LWG 3498 seems to miss the non-member ``swap`` for ``basic_syncbuf`` ","February 2022","",""
"`3618 <https://wg21.link/LWG3618>`__","Unnecessary ``iter_move`` for ``transform_view::iterator`` ","February 2022","","","|ranges|"
"`3618 <https://wg21.link/LWG3618>`__","Unnecessary ``iter_move`` for ``transform_view::iterator`` ","February 2022","|Complete|","19.0","|ranges|"
"`3619 <https://wg21.link/LWG3619>`__","Specification of ``vformat_to`` contains ill-formed ``formatted_size`` calls","February 2022","|Nothing to do|","","|format|"
"`3621 <https://wg21.link/LWG3621>`__","Remove feature-test macro ``__cpp_lib_monadic_optional`` ","February 2022","|Complete|","15.0"
"`3632 <https://wg21.link/LWG3632>`__","``unique_ptr`` ""Mandates: This constructor is not selected by class template argument deduction""","February 2022","|Nothing to do|",""

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7
libcxx/include/__ranges/transform_view.h
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@ -326,13 +326,6 @@ public:
{
return __x.__current_ - __y.__current_;
}
_LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto) iter_move(const __iterator& __i) noexcept(noexcept(*__i)) {
if constexpr (is_lvalue_reference_v<decltype(*__i)>)
return std::move(*__i);
else
return *__i;
}
};
# if _LIBCPP_STD_VER >= 23

2
libcxx/test/std/ranges/range.adaptors/range.transform/iterator/deref.pass.cpp
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@ -37,7 +37,7 @@ int main(int, char**) {
using View = std::ranges::transform_view<MoveOnlyView, PlusOneNoexcept>;
View transformView(MoveOnlyView{buff}, PlusOneNoexcept{});
assert(*transformView.begin() == 1);
LIBCPP_ASSERT_NOEXCEPT(*std::declval<std::ranges::iterator_t<View>>());
ASSERT_NOEXCEPT(*std::declval<std::ranges::iterator_t<View>>());
ASSERT_SAME_TYPE(int, decltype(*std::declval<View>().begin()));
}
{

49
libcxx/test/std/ranges/range.adaptors/range.transform/iterator/iter_move.pass.cpp
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@ -1,49 +0,0 @@
//===----------------------------------------------------------------------===//
//
// 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
// friend constexpr decltype(auto) iter_move(const iterator& i)
// noexcept(noexcept(invoke(i.parent_->fun_, *i.current_)))
#include <ranges>
#include "test_macros.h"
#include "../types.h"
constexpr bool test() {
int buff[8] = {0, 1, 2, 3, 4, 5, 6, 7};
{
std::ranges::transform_view transformView(MoveOnlyView{buff}, PlusOneMutable{});
auto iter = transformView.begin();
ASSERT_NOT_NOEXCEPT(std::ranges::iter_move(iter));
assert(std::ranges::iter_move(iter) == 1);
assert(std::ranges::iter_move(iter + 2) == 3);
ASSERT_SAME_TYPE(int, decltype(std::ranges::iter_move(iter)));
ASSERT_SAME_TYPE(int, decltype(std::ranges::iter_move(std::move(iter))));
}
{
LIBCPP_ASSERT_NOEXCEPT(std::ranges::iter_move(
std::declval<std::ranges::iterator_t<std::ranges::transform_view<MoveOnlyView, PlusOneNoexcept>>&>()));
ASSERT_NOT_NOEXCEPT(std::ranges::iter_move(
std::declval<std::ranges::iterator_t<std::ranges::transform_view<MoveOnlyView, PlusOneMutable>>&>()));
}
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}