[clang-tools-extra] [clang-tidy] fix false positive of parentheses removal for overloaded operator (PR #192254)

[Gaurav Dhingra via cfe-commits]

https://github.com/gxyd created https://github.com/llvm/llvm-project/pull/192254

Fixes #189217
    
don't remove necessary parentheses for an overloaded operator, when
the parenthese occurs in the context of a binary operation
    
E.g. (E1 & E2) != E3       // the brackets aren't redundant here
E.g. (E1 & E2)             // brackets are redundant here

>From 4f18cbfc0ced5713956b4390b7fc36e29dd9737b Mon Sep 17 00:00:00 2001
From: Gaurav Dhingra <gauravdhingra.gxyd at gmail.com>
Date: Wed, 15 Apr 2026 18:23:01 +0530
Subject: [PATCH 1/2] [clang-tidy] fix false positive of parentheses removal
 for overloaded operator

Fixes #189217

don't remove necessary parentheses for an overloaded operator, when
the parenthese occurs in the context of a binary operation

E.g. (E1 & E2) != E3       // the brackets aren't redundant here
E.g. (E1 & E2)             // brackets are redundant here
---
 .../readability/RedundantParenthesesCheck.cpp |  4 ++-
 .../readability/redundant-parentheses.cpp     | 33 +++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clang-tidy/readability/RedundantParenthesesCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantParenthesesCheck.cpp
index 9b3948a1c50c0..f1056ad3712e3 100644
--- a/clang-tools-extra/clang-tidy/readability/RedundantParenthesesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantParenthesesCheck.cpp
@@ -58,7 +58,9 @@ void RedundantParenthesesCheck::registerMatchers(MatchFinder *Finder) {
                     memberExpr(), callExpr())),
                 unless(anyOf(isInMacro(),
                              // sizeof(...) is common used.
-                             hasParent(unaryExprOrTypeTraitExpr()))))
+                             hasParent(unaryExprOrTypeTraitExpr()),
+                             allOf(hasDescendant(cxxOperatorCallExpr()),
+                                   hasParent(binaryOperator())))))
           .bind("dup"),
       this);
 }
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-parentheses.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-parentheses.cpp
index 9a8a0d4d73483..6dad9ef1086e3 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-parentheses.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-parentheses.cpp
@@ -121,3 +121,36 @@ void memberExpr() {
    // CHECK-FIXES:    if (foo.fooBar().z) {
   }
 }
+
+enum class FoldLevel {
+  None = 0x0,
+  HeaderFlag = 0x2000,
+};
+
+constexpr FoldLevel operator&(FoldLevel lhs, FoldLevel rhs) {
+  return static_cast<FoldLevel>(static_cast<int>(lhs) & static_cast<int>(rhs));
+}
+
+constexpr bool UseOperatorAmpersand1(FoldLevel level) {
+  return (level & FoldLevel::HeaderFlag) != FoldLevel::None;
+}
+
+constexpr bool UseOperatorAmpersand2(FoldLevel level) {
+  const FoldLevel l = (level & FoldLevel::HeaderFlag);
+  // CHECK-MESSAGES: :[[@LINE-1]]:23: warning: redundant parentheses around expression [readability-redundant-parentheses]
+  // CHECK-FIXES:    const FoldLevel l = level & FoldLevel::HeaderFlag;
+  return l != FoldLevel::None;
+}
+
+constexpr bool UseOperatorAmpersand3(FoldLevel level) {
+  const FoldLevel l = level & FoldLevel::HeaderFlag;
+  return (l != FoldLevel::None);
+}
+
+constexpr bool UseOperatorAmpersand4(FoldLevel level) {
+  return ((level & FoldLevel::HeaderFlag) != FoldLevel::None);
+}
+
+const int bracket_int_plus_num = (4) + 5;
+// CHECK-MESSAGES: :[[@LINE-1]]:34: warning: redundant parentheses around expression [readability-redundant-parentheses]
+// CHECK-FIXES:    const int bracket_int_plus_num = 4 + 5;

>From 9aeb644a5ea0183b703a61bda184cc4c38722027 Mon Sep 17 00:00:00 2001
From: Gaurav Dhingra <gauravdhingra.gxyd at gmail.com>
Date: Wed, 15 Apr 2026 18:32:19 +0530
Subject: [PATCH 2/2] add release notes entry

---
 clang-tools-extra/docs/ReleaseNotes.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 6979c2cbcfff2..74e4d8c8995c7 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -513,6 +513,11 @@ Changes in existing checks
   `IgnoreMacros` option to suppress warnings when the initializer involves
   macros that may expand differently in other configurations.
 
+- Improved :doc:`readability-redundant-parentheses
+  <clang-tidy/checks/readability/redundant-parentheses>` check by fixing a
+  false positive for parentheses present around an overloaded operator in the
+  context of a binary operation.
+
 - Improved :doc:`readability-redundant-preprocessor
   <clang-tidy/checks/readability/redundant-preprocessor>` check by fixing a
   false positive for nested ``#if`` directives using different builtin