[libcxx-commits] [libcxx] 3d7622e - [libc++][ranges] LWG3618: Unnecessary `iter_move` for `transform_view::iterator` (#91809)

[via libcxx-commits]

Author: Xiaoyang Liu
Date: 2024-07-22T18:32:37+02:00
New Revision: 3d7622ea0bd443bb6ccb58d6b33e8cf52a8f0f4e

URL: https://github.com/llvm/llvm-project/commit/3d7622ea0bd443bb6ccb58d6b33e8cf52a8f0f4e
DIFF: https://github.com/llvm/llvm-project/commit/3d7622ea0bd443bb6ccb58d6b33e8cf52a8f0f4e.diff

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

## 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)

Added: 
    

Modified: 
    libcxx/docs/Status/Cxx23Issues.csv
    libcxx/include/__ranges/transform_view.h
    libcxx/test/std/ranges/range.adaptors/range.transform/iterator/deref.pass.cpp

Removed: 
    libcxx/test/std/ranges/range.adaptors/range.transform/iterator/iter_move.pass.cpp


################################################################################
diff  --git a/libcxx/docs/Status/Cxx23Issues.csv b/libcxx/docs/Status/Cxx23Issues.csv
index 50104052effad..1f35ca5713a9b 100644
--- a/libcxx/docs/Status/Cxx23Issues.csv
+++ b/libcxx/docs/Status/Cxx23Issues.csv
@@ -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|",""

diff  --git a/libcxx/include/__ranges/transform_view.h b/libcxx/include/__ranges/transform_view.h
index dc3aaa59ed8c3..bcce389c0e680 100644
--- a/libcxx/include/__ranges/transform_view.h
+++ b/libcxx/include/__ranges/transform_view.h
@@ -326,13 +326,6 @@ class transform_view<_View, _Fn>::__iterator : public __transform_view_iterator_
   {
     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

diff  --git a/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/deref.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/deref.pass.cpp
index 06eb91dba22ff..5d8bf51c69696 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/deref.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/deref.pass.cpp
@@ -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()));
   }
   {

diff  --git a/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/iter_move.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/iter_move.pass.cpp
deleted file mode 100644
index ea1e4b61412c4..0000000000000
--- a/libcxx/test/std/ranges/range.adaptors/range.transform/iterator/iter_move.pass.cpp
+++ /dev/null
@@ -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;
-}