[clang-tools-extra] [clang-tidy] Ignore non-forwarded arguments if they are unnamed (PR #87832)

[Danny Mösch via cfe-commits]

https://github.com/SimplyDanny created https://github.com/llvm/llvm-project/pull/87832

Fixes #87697.

>From b8662eb6681d86ac475f30a70740b6b83eda1de3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Danny=20M=C3=B6sch?= <danny.moesch at icloud.com>
Date: Fri, 5 Apr 2024 23:41:50 +0200
Subject: [PATCH] [clang-tidy] Ignore non-forwarded arguments if they are
 unnamed

---
 .../cppcoreguidelines/MissingStdForwardCheck.cpp  | 15 +++++++++------
 clang-tools-extra/docs/ReleaseNotes.rst           |  4 ++++
 .../cppcoreguidelines/missing-std-forward.cpp     |  3 +++
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
index 87fd8adf997082..6817bcb24c8112 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
@@ -79,6 +79,8 @@ AST_MATCHER_P(LambdaExpr, hasCaptureDefaultKind, LambdaCaptureDefault, Kind) {
   return Node.getCaptureDefault() == Kind;
 }
 
+AST_MATCHER(ParmVarDecl, hasAnyName) { return !Node.getName().empty(); }
+
 } // namespace
 
 void MissingStdForwardCheck::registerMatchers(MatchFinder *Finder) {
@@ -125,12 +127,13 @@ void MissingStdForwardCheck::registerMatchers(MatchFinder *Finder) {
                    hasAncestor(expr(hasUnevaluatedContext())))));
 
   Finder->addMatcher(
-      parmVarDecl(parmVarDecl().bind("param"), isTemplateTypeParameter(),
-                  hasAncestor(functionDecl().bind("func")),
-                  hasAncestor(functionDecl(
-                      isDefinition(), equalsBoundNode("func"), ToParam,
-                      unless(anyOf(isDeleted(), hasDescendant(std::move(
-                                                    ForwardCallMatcher))))))),
+      parmVarDecl(
+          parmVarDecl().bind("param"), hasAnyName(), isTemplateTypeParameter(),
+          hasAncestor(functionDecl().bind("func")),
+          hasAncestor(functionDecl(
+              isDefinition(), equalsBoundNode("func"), ToParam,
+              unless(anyOf(isDeleted(),
+                           hasDescendant(std::move(ForwardCallMatcher))))))),
       this);
 }
 
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 456e09204fa2f9..f79d3b9f362063 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -182,6 +182,10 @@ Changes in existing checks
   giving false positives for deleted functions and fix false negative when some
   parameters are forwarded, but other aren't.
 
+- Improved :doc:`cppcoreguidelines-missing-std-forward
+  <clang-tidy/checks/cppcoreguidelines/missing-std-forward>` check by ignoring
+  parameters without a name (unused arguments).
+
 - Improved :doc:`cppcoreguidelines-owning-memory
   <clang-tidy/checks/cppcoreguidelines/owning-memory>` check to properly handle
   return type in lambdas and in nested functions.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
index 9a50eabf619bd5..c435a0e023ba0b 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
@@ -198,3 +198,6 @@ struct S {
 };
 
 } // namespace deleted_functions
+
+template<typename F>
+void unused_argument(F&&) {}