[clang-tidy] Ignore unused parameters in rvalue-reference-param-not-moved check

[AMS21]

With this patch we no longer issue a warning for unused parameters which are marked as such.

This fixes #68209

[llvmbot]

@llvm/pr-subscribers-clang-tidy

Author: None (AMS21)

Changes

With this patch we no longer issue a warning for unused parameters which are marked as such.

This fixes #68209

---

Full diff: https://github.com/llvm/llvm-project/pull/69045.diff

3 Files Affected:

• (modified) clang-tools-extra/clang-tidy/cppcoreguidelines/RvalueReferenceParamNotMovedCheck.cpp (+3)
• (modified) clang-tools-extra/docs/ReleaseNotes.rst (+4)
• (modified) clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/rvalue-reference-param-not-moved.cpp (+19)

diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/RvalueReferenceParamNotMovedCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/RvalueReferenceParamNotMovedCheck.cpp
index efcaffb45d9ad8a..88b00dc17470f32 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/RvalueReferenceParamNotMovedCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/RvalueReferenceParamNotMovedCheck.cpp
@@ -84,6 +84,9 @@ void RvalueReferenceParamNotMovedCheck::check(
   if (IgnoreUnnamedParams && Param->getName().empty())
     return;
 
+  if (!Param->isUsed() && Param->hasAttr<UnusedAttr>())
+    return;
+
   const auto *Function = dyn_cast<FunctionDecl>(Param->getDeclContext());
   if (!Function)
     return;
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 03e5dc6f164af2a..c732d4904df13fa 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -237,6 +237,10 @@ Changes in existing checks
   <clang-tidy/checks/cppcoreguidelines/pro-type-vararg>` check to ignore
   false-positives in unevaluated context (e.g., ``decltype``, ``sizeof``, ...).
 
+- Improved :doc:`cppcoreguidelines-rvalue-reference-param-not-moved
+  <clang-tidy/checks/cppcoreguidelines/rvalue-reference-param-not-moved>` check
+  to ignore unused parameters when they are marked as unused.
+
 - Improved :doc:`llvm-namespace-comment
   <clang-tidy/checks/llvm/namespace-comment>` check to provide fixes for
   ``inline`` namespaces in the same format as :program:`clang-format`.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/rvalue-reference-param-not-moved.cpp b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/rvalue-reference-param-not-moved.cpp
index 8f8e272e1e8a90d..c6a70aef810ac90 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/rvalue-reference-param-not-moved.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/rvalue-reference-param-not-moved.cpp
@@ -333,3 +333,22 @@ void instantiate_a_class_template() {
   AClassTemplate<Obj&> withObjRef(o);
   withObjRef.never_moves(o);
 }
+
+namespace gh68209
+{
+  void f1([[maybe_unused]] int&& x) {}
+
+  void f2(__attribute__((unused)) int&& x) {}
+
+  void f3(int&& x) {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: rvalue reference parameter 'x' is never moved from inside the function body [cppcoreguidelines-rvalue-reference-param-not-moved]
+
+  template <typename T>
+  void f4([[maybe_unused]] T&& x) {}
+
+  template <typename T>
+  void f5(__attribute((unused)) T&& x) {}
+
+  template<typename T>
+  void f6(T&& x) {}
+} // namespace gh68209

[AMS21]

I'm not sure if we should rather have this as an option like IgnoreUnnamedParams

[PiotrZSL]

Looks fine, I don't thing that this needs to be configurable.
If someone put explicitly attribute, then there is assumption that such param can be unused.

[AMS21]

Added the suggested change and also added another test case

[AMS21]

If there are no more problems I would kindly ask for someone to push this on my behalf :)