[clang-tools-extra] [clang-tidy]avoid bugprone-unused-return-value false positive for assignment operator overloading (PR #84489)

[Congcong Cai via cfe-commits]

https://github.com/HerrCai0907 created https://github.com/llvm/llvm-project/pull/84489

Fixes: #84480
We assuem assignemnt at most of time, operator overloading means the value is assigned to the other variable, then clang-tidy should suppress warning even if this operator overloading match the regex.


>From b87bb6b65099228ff7ded13da059215d59d794d5 Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0907 at 163.com>
Date: Fri, 8 Mar 2024 22:15:20 +0800
Subject: [PATCH] [clang-tidy]avoid bugprone-unused-return-value false positive
 for assignment operator overloading

Fixes: #84480
We assuem assignemnt at most of time, operator overloading means the value is assigned to the other variable, then clang-tidy should suppress warning even if this operator overloading match the regex.
---
 .../bugprone/UnusedReturnValueCheck.cpp       | 24 +++++++++++--------
 clang-tools-extra/docs/ReleaseNotes.rst       |  4 ++--
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
index 1252b2f23805a1..2167d381c42b03 100644
--- a/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnusedReturnValueCheck.cpp
@@ -11,6 +11,7 @@
 #include "../utils/OptionsUtils.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
 
 using namespace clang::ast_matchers;
 using namespace clang::ast_matchers::internal;
@@ -157,16 +158,19 @@ void UnusedReturnValueCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
 }
 
 void UnusedReturnValueCheck::registerMatchers(MatchFinder *Finder) {
-  auto MatchedDirectCallExpr =
-      expr(callExpr(callee(functionDecl(
-                        // Don't match void overloads of checked functions.
-                        unless(returns(voidType())),
-                        anyOf(isInstantiatedFrom(matchers::matchesAnyListedName(
-                                  CheckedFunctions)),
-                              returns(hasCanonicalType(hasDeclaration(
-                                  namedDecl(matchers::matchesAnyListedName(
-                                      CheckedReturnTypes)))))))))
-               .bind("match"));
+  auto MatchedDirectCallExpr = expr(
+      callExpr(callee(functionDecl(
+                   // Don't match void overloads of checked functions.
+                   unless(returns(voidType())),
+                   // Don't match copy or move assignment operator.
+                   unless(cxxMethodDecl(anyOf(isCopyAssignmentOperator(),
+                                              isMoveAssignmentOperator()))),
+                   anyOf(isInstantiatedFrom(
+                             matchers::matchesAnyListedName(CheckedFunctions)),
+                         returns(hasCanonicalType(hasDeclaration(
+                             namedDecl(matchers::matchesAnyListedName(
+                                 CheckedReturnTypes)))))))))
+          .bind("match"));
 
   auto CheckCastToVoid =
       AllowCastToVoid ? castExpr(unless(hasCastKind(CK_ToVoid))) : castExpr();
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index b5f025ce467a15..c7121fe07e0ad3 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -152,9 +152,9 @@ Changes in existing checks
 
 - Improved :doc:`bugprone-unused-return-value
   <clang-tidy/checks/bugprone/unused-return-value>` check by updating the
-  parameter `CheckedFunctions` to support regexp and avoiding false postive for
+  parameter `CheckedFunctions` to support regexp, avoiding false positive for
   function with the same prefix as the default argument, e.g. ``std::unique_ptr``
-  and ``std::unique``.
+  and ``std::unique``, avoiding false positive for assignment operator overloading.
 
 - Improved :doc:`bugprone-use-after-move
   <clang-tidy/checks/bugprone/use-after-move>` check to also handle