[libc++] Implements LWG3953

[NoumanAmir657]

Closes #105303

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: NoumanAmir-10xe (NoumanAmir657)

Changes

For the issue: #105303
LWG3953

---

Full diff: https://github.com/llvm/llvm-project/pull/107535.diff

2 Files Affected:

• (modified) libcxx/include/__iterator/common_iterator.h (+1-1)
• (modified) libcxx/include/__iterator/counted_iterator.h (+1-1)

diff --git a/libcxx/include/__iterator/common_iterator.h b/libcxx/include/__iterator/common_iterator.h
index 199de2cc7337b0..ff382f32fe8950 100644
--- a/libcxx/include/__iterator/common_iterator.h
+++ b/libcxx/include/__iterator/common_iterator.h
@@ -235,7 +235,7 @@ class common_iterator {
     return std::__unchecked_get<_Sent>(__x.__hold_) - std::__unchecked_get<_I2>(__y.__hold_);
   }
 
-  _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto)
   iter_move(const common_iterator& __i) noexcept(noexcept(ranges::iter_move(std::declval<const _Iter&>())))
     requires input_iterator<_Iter>
   {
diff --git a/libcxx/include/__iterator/counted_iterator.h b/libcxx/include/__iterator/counted_iterator.h
index ea2832e3b978dc..a02c61bf34e2f9 100644
--- a/libcxx/include/__iterator/counted_iterator.h
+++ b/libcxx/include/__iterator/counted_iterator.h
@@ -249,7 +249,7 @@ class counted_iterator
     return __rhs.__count_ <=> __lhs.__count_;
   }
 
-  _LIBCPP_HIDE_FROM_ABI friend constexpr iter_rvalue_reference_t<_Iter>
+  _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto)
   iter_move(const counted_iterator& __i) noexcept(noexcept(ranges::iter_move(__i.__current_)))
     requires input_iterator<_Iter>
   {

[frederick-vs-ja]

For the issue:

It would be better to use GitHub's close/fix/resolve syntax in the PR description to associate this PR with the issue.

Also, it's better to explicitly say LWG3953 in the title of this PR. Note that the actual return types remain unchanged.

[NoumanAmir657]

For the issue:

It would be better to use GitHub's close/fix/resolve syntax in the PR description to associate this PR with the issue.

Also, it's better to explicitly say LWG3953 in the title of this PR. Note that the actual return types remain unchanged.

Fixed.

[frederick-vs-ja]

No change requested. The modification is almost, if not exactly, NFC, given input_iterator has already required that iter_rvalue_reference_t is valid.

It would be extremely weird to me to test something (if exists) for which iter_rvalue_reference_t results in substitution failure while input_iterator gives hard error (caused by some stuff checked before iter_rvalue_reference_t).

[Zingam]

You still need to update the cvs file I think:

llvm-project/libcxx/docs/Status/Cxx2cIssues.csv

Line 33 in 86835d2

"`LWG3953 <https://wg21.link/LWG3953>`__","``iter_move`` for ``common_iterator`` and ``counted_iterator`` should return ``decltype(auto)``","2023-11 (Kona)","","",""

[NoumanAmir657]

You still need to update the cvs file I think:

llvm-project/libcxx/docs/Status/Cxx2cIssues.csv

Line 33 in 86835d2

"`LWG3953 <https://wg21.link/LWG3953>`__","``iter_move`` for ``common_iterator`` and ``counted_iterator`` should return ``decltype(auto)``","2023-11 (Kona)","","",""

Updated. Thanks!

[NoumanAmir657]

Any idea why the CI failed? @frederick-vs-ja @Zingam .

[Zingam]

Any idea why the CI failed? @frederick-vs-ja @Zingam .

I restarted the failed CI job. Let's wait to see if it will pass.

[NoumanAmir657]

Any idea why the CI failed? @frederick-vs-ja @Zingam .

I restarted the failed CI job. Let's wait an see if it will pass.

Aha okay. Thanks.

[NoumanAmir657]

Any idea why the CI failed? @frederick-vs-ja @Zingam .

I restarted the failed CI job. Let's wait to see if it will pass.

Yeah seems like it passed now.

[ldionne]

@NoumanAmir657 Thanks for the patch! Please turn off the "hide my email" feature of Github for your future contributions since we require a valid email address for LLVM contributions.