release/21.x: [libc++][docs] Add missing entry for P3379R0 to 21.rst

[frederick-vs-ja]

P3379R0 was implemented in LLVM 21 (13c464b) but the entry for release note is still missing. A following-up PR (4a509f8) fixed this as drive-by but backport was not accepted.

This patch only adds the missing entry.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: A. Jiang (frederick-vs-ja)

Changes

P3379R0 was implemented in LLVM 21 (13c464b) but the entry for release note is still missing. A following-up PR (4a509f8) fixed this as drive-by but backport was not accepted.

This patch only adds the missing entry.

---

Full diff: https://github.com/llvm/llvm-project/pull/163756.diff

1 Files Affected:

• (modified) libcxx/docs/ReleaseNotes/21.rst (+1)

diff --git a/libcxx/docs/ReleaseNotes/21.rst b/libcxx/docs/ReleaseNotes/21.rst
index 1410223d56a6f..d6765eb62e4b0 100644
--- a/libcxx/docs/ReleaseNotes/21.rst
+++ b/libcxx/docs/ReleaseNotes/21.rst
@@ -53,6 +53,7 @@ Implemented Papers
 - P2711R1: Making multi-param constructors of ``views`` ``explicit`` (`Github <https://github.com/llvm/llvm-project/issues/105252>`__)
 - P2770R0: Stashing stashing ``iterators`` for proper flattening (`Github <https://github.com/llvm/llvm-project/issues/105250>`__)
 - P2655R3: ``common_reference_t`` of ``reference_wrapper`` Should Be a Reference Type (`Github <https://github.com/llvm/llvm-project/issues/105260>`__)
+- P3379R0: Constrain ``std::expected equality`` operators (`Github <https://github.com/llvm/llvm-project/issues/118135>`__)
 
 Improvements and New Features
 -----------------------------

[Zingam]

Does this need to be 'backported'?

[github-actions]

@frederick-vs-ja (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.