[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 6dff411516cb4c0e807307fd36d15955e805d5c4 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   | 23 ++++++++++------
 clang-tools-extra/docs/ReleaseNotes.rst       |  4 +++
 .../modernize/use-default-member-init.cpp     | 26 +++++++++++++++++++
 3 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
index 6c06b0af342f6..d01f440fe7e16 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();
@@ -194,15 +200,16 @@ void UseDefaultMemberInitCheck::storeOptions(
 }
 
 void UseDefaultMemberInitCheck::registerMatchers(MatchFinder *Finder) {
+  auto NumericLiteral = anyOf(integerLiteral(), floatLiteral());
+  auto UnaryNumericLiteral = unaryOperator(hasAnyOperatorName("+", "-"), hasUnaryOperand(NumericLiteral));
+  auto EnumRef = declRefExpr(to(enumConstantDecl()));
+
   auto InitBase =
-      anyOf(stringLiteral(), characterLiteral(), integerLiteral(),
-            unaryOperator(hasAnyOperatorName("+", "-"),
-                          hasUnaryOperand(integerLiteral())),
-            floatLiteral(),
-            unaryOperator(hasAnyOperatorName("+", "-"),
-                          hasUnaryOperand(floatLiteral())),
-            cxxBoolLiteral(), cxxNullPtrLiteralExpr(), implicitValueInitExpr(),
-            declRefExpr(to(enumConstantDecl())));
+      anyOf(stringLiteral(), characterLiteral(), NumericLiteral, UnaryNumericLiteral,
+            cxxBoolLiteral(), cxxNullPtrLiteralExpr(), implicitValueInitExpr(), EnumRef,
+            binaryOperator(hasLHS(anyOf(NumericLiteral, EnumRef, binaryOperator())),
+                           hasRHS(anyOf(NumericLiteral, EnumRef, 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..01892f4cde648 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -128,6 +128,10 @@ Changes in existing checks
   <clang-tidy/checks/misc/redundant-expression>` check by providing additional
   examples and fixing some macro related false positives.
 
+- Improved :doc:`modernize-use-default-member-init
+  <clang-tidy/checks/modernize/use-default-member-init>` check by matching arithmetic
+  operations within member list initialization.
+
 - Improved :doc:`performance/unnecessary-value-param
   <clang-tidy/checks/performance/unnecessary-value-param>` check performance by
   tolerating fix-it breaking compilation when functions is used as pointers 
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