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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Xiaoyang Liu (xiaoyang-sde)

<details>
<summary>Changes</summary>

## 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)

---
Full diff: https://github.com/llvm/llvm-project/pull/91809.diff


2 Files Affected:

- (modified) libcxx/docs/Status/Cxx23Issues.csv (+1-1) 
- (modified) libcxx/include/__ranges/transform_view.h (-7) 


``````````diff
diff --git a/libcxx/docs/Status/Cxx23Issues.csv b/libcxx/docs/Status/Cxx23Issues.csv
index 04f6e23375acd..55db4d209a407 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

``````````

</details>


https://github.com/llvm/llvm-project/pull/91809