[libc++][docs] Update [[nodiscard]] coding guidelines (llvm#178384)

H-G-Hristov · philnik777 · Zingam · web-flow · commit e6c73eb0c4c3 · 2026-02-09T18:44:45.000+02:00
as requested in llvm#176936 (review) Clarifies when not to apply `[[nodiscard]]`. https://libcxx.llvm.org/CodingGuidelines.html#apply-nodiscard-where-relevant --------- Co-authored-by: Nikolas Klauser <nikolasklauser@berlin.de> Co-authored-by: Hristo Hristov <zingam@outlook.com>
diff --git a/libcxx/docs/CodingGuidelines.rst b/libcxx/docs/CodingGuidelines.rst
@@ -175,7 +175,10 @@ have a recommended practice where to put them, so libc++ applies it whenever it
   This protects programmers from assuming too much about how the internals of a function work, making code more robust
   in the presence of future optimizations.
 
-``[[nodiscard]]`` should not be applied to conversion functions because Clang already diagnoses unused cast results.
+``[[nodiscard]]`` should not be applied to functions if Clang already diagnoses unused results, for example:
+- conversion functions
+- equality operators
+- relational operators
 
 Applications of ``[[nodiscard]]`` are code like any other code, so we aim to test them on public interfaces. This can be
 done with a ``.verify.cpp`` test. Many examples are available. Just look for tests with the suffix
