[clang-tidy] Fix parentheses handling in readability-math-missing-parentheses (#172423)

Previously, the check would stop AST traversal when encountering a
`ParenExpr`. This PR fixes this problem

Closes #172269

Author: zeyi2

clang-tools-extra/clang-tidy/readability/MathMissingParenthesesCheck.cpp

@@ -48,11 +48,17 @@ static int getPrecedence(const BinaryOperator *BinOp) {
     return 0;
   }
 }
-static void addParentheses(const BinaryOperator *BinOp,
-                           const BinaryOperator *ParentBinOp,
+static void addParentheses(const Expr *E, const BinaryOperator *ParentBinOp,
                            ClangTidyCheck *Check,
                            const clang::SourceManager &SM,
                            const clang::LangOptions &LangOpts) {
+  if (const auto *Paren = dyn_cast<ParenExpr>(E)) {
+    addParentheses(Paren->getSubExpr()->IgnoreImpCasts(), nullptr, Check, SM,
+                   LangOpts);
+    return;
+  }
+
+  const auto *BinOp = dyn_cast<BinaryOperator>(E);
   if (!BinOp)
     return;
 
@@ -81,10 +87,8 @@ static void addParentheses(const BinaryOperator *BinOp,
     }
   }
 
-  addParentheses(dyn_cast<BinaryOperator>(BinOp->getLHS()->IgnoreImpCasts()),
-                 BinOp, Check, SM, LangOpts);
-  addParentheses(dyn_cast<BinaryOperator>(BinOp->getRHS()->IgnoreImpCasts()),
-                 BinOp, Check, SM, LangOpts);
+  addParentheses(BinOp->getLHS()->IgnoreImpCasts(), BinOp, Check, SM, LangOpts);
+  addParentheses(BinOp->getRHS()->IgnoreImpCasts(), BinOp, Check, SM, LangOpts);
 }
 
 void MathMissingParenthesesCheck::check(

clang-tools-extra/docs/ReleaseNotes.rst

@@ -619,6 +619,10 @@ Changes in existing checks
   by not enforcing parameter name consistency between a variadic parameter pack
   in the primary template and specific parameters in its specializations.
 
+- Improved :doc:`readability-math-missing-parentheses
+  <clang-tidy/checks/readability/math-missing-parentheses>` check by correctly
+  diagnosing operator precedence issues inside parenthesized expressions.
+
 - Improved :doc:`readability-qualified-auto
   <clang-tidy/checks/readability/qualified-auto>` check by adding the option
   `IgnoreAliasing`, that allows not looking at underlying types of type aliases.

clang-tools-extra/test/clang-tidy/checkers/readability/math-missing-parentheses.cpp

@@ -173,3 +173,22 @@ void CompareAsParentBinOp(int b) {
 
   }
 }
+
+void test_with_parentheses() {
+  // CHECK-MESSAGES: :[[@LINE+2]]:14: warning: '/' has higher precedence than '-'; add parentheses to explicitly specify the order of operations [readability-math-missing-parentheses]
+  // CHECK-FIXES: int z = (2-(4*3/2)) / (3-1);
+  int z = (2-4*3/2) / (3-1);
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:14: warning: '/' has higher precedence than '-'; add parentheses to explicitly specify the order of operations [readability-math-missing-parentheses]
+  // CHECK-FIXES: int x = (2-(4*3/2));
+  int x = (2-4*3/2);
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:17: warning: '*' has higher precedence than '+'; add parentheses to explicitly specify the order of operations [readability-math-missing-parentheses]
+  // CHECK-FIXES: int y = ((1 + (2 * 3)));
+  int y = ((1 + 2 * 3));
+
+  short s = 0;
+  // CHECK-MESSAGES: :[[@LINE+2]]:13: warning: '*' has higher precedence than '+'; add parentheses to explicitly specify the order of operations [readability-math-missing-parentheses]
+  // CHECK-FIXES: s = ((1 + (2 * 3)));
+  s = ((1 + 2 * 3));
+}