[clang-tools-extra] [clang-tidy] detect arithmetic operations within member list initialization in modernize-use-default-member-init check (PR #129370)

[David Rivera via cfe-commits]

https://github.com/RiverDave updated https://github.com/llvm/llvm-project/pull/129370

>From 68c371939323c9be13dba2e8e80ac4138859d845 Mon Sep 17 00:00:00 2001
From: David Rivera <davidriverg at gmail.com>
Date: Sat, 1 Mar 2025 02:09:02 -0500
Subject: [PATCH] [clang-tidy] detect arithmetic operations within member list
 initialization in modernize-use-default-member-init

---
 .../modernize/UseDefaultMemberInitCheck.cpp   | 14 +++++++++-
 clang-tools-extra/docs/ReleaseNotes.rst       |  4 +++
 .../modernize/use-default-member-init.cpp     | 26 +++++++++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
index 6c06b0af342f6..d155207d2a3ea 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
@@ -159,6 +159,12 @@ static bool sameValue(const Expr *E1, const Expr *E2) {
   case Stmt::UnaryOperatorClass:
     return sameValue(cast<UnaryOperator>(E1)->getSubExpr(),
                      cast<UnaryOperator>(E2)->getSubExpr());
+  case Stmt::BinaryOperatorClass: {
+    const auto *BinOp1 = cast<BinaryOperator>(E1);
+    const auto *BinOp2 = cast<BinaryOperator>(E2);
+    return sameValue(BinOp1->getLHS(), BinOp2->getLHS()) &&
+           sameValue(BinOp1->getRHS(), BinOp2->getRHS());
+  }
   case Stmt::CharacterLiteralClass:
     return cast<CharacterLiteral>(E1)->getValue() ==
            cast<CharacterLiteral>(E2)->getValue();
@@ -202,7 +208,13 @@ void UseDefaultMemberInitCheck::registerMatchers(MatchFinder *Finder) {
             unaryOperator(hasAnyOperatorName("+", "-"),
                           hasUnaryOperand(floatLiteral())),
             cxxBoolLiteral(), cxxNullPtrLiteralExpr(), implicitValueInitExpr(),
-            declRefExpr(to(enumConstantDecl())));
+            declRefExpr(to(enumConstantDecl())),
+            binaryOperator(hasLHS(anyOf(integerLiteral(), floatLiteral(),
+                                        declRefExpr(to(enumConstantDecl())),
+                                        binaryOperator())),
+                           hasRHS(anyOf(integerLiteral(), floatLiteral(),
+                                        declRefExpr(to(enumConstantDecl())),
+                                        binaryOperator()))));
 
   auto Init =
       anyOf(initListExpr(anyOf(allOf(initCountIs(1), hasInit(0, InitBase)),
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 07a79d6bbe807..6d909f9d7c6bd 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -137,6 +137,10 @@ Changes in existing checks
   <clang-tidy/checks/performance/move-const-arg>` check by fixing false negatives
   on ternary operators calling ``std::move``.
 
+- Improved :doc:`modernize-use-default-member-init
+  <clang-tidy/checks/modernize/use-default-member-init>` check by matching arithmetic
+  operations within member list initialization.
+
 Removed checks
 ^^^^^^^^^^^^^^
 
diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-default-member-init.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-default-member-init.cpp
index 81c980e0217e6..ff8c80b682bdb 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-default-member-init.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-default-member-init.cpp
@@ -518,3 +518,29 @@ class ArrayBraceInitMultipleValues {
 };
 
 } // namespace PR63285
+
+namespace PR122480 {
+
+#define ARITHMETIC_MACRO (44 - 2)
+
+class DefaultMemberInitWithArithmetic {
+  DefaultMemberInitWithArithmetic() : a{1 + 1},  b{1 + 11 + 123 + 1234},  c{2 + (4 / 2) + 3 + (7 / 11)},  d{ARITHMETIC_MACRO * 2}, e{1.2 + 3.4} {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:39: warning: member initializer for 'a' is redundant [modernize-use-default-member-init]
+  // CHECK-FIXES: DefaultMemberInitWithArithmetic()  {}
+
+  int a{1 + 1};
+  int b;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'b' [modernize-use-default-member-init]
+  // CHECK-FIXES:  int b{1 + 11 + 123 + 1234};
+  int c;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'c' [modernize-use-default-member-init]
+  // CHECK-FIXES: int c{2 + (4 / 2) + 3 + (7 / 11)}
+  int d;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'd' [modernize-use-default-member-init]
+  // CHECK-FIXES: int d{ARITHMETIC_MACRO * 2};
+  double e;
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: use default member initializer for 'e' [modernize-use-default-member-init]
+  // CHECK-FIXES: double e{1.2 + 3.4};
+
+};
+} // namespace PR122480