[clang-tools-extra] Add clang-tidy check readability-math-missing-parentheses (PR #84481)

[Julian Schmidt via cfe-commits]

================
@@ -0,0 +1,68 @@
+//===--- MathMissingParenthesesCheck.cpp - clang-tidy ---------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "MathMissingParenthesesCheck.h"
+#include "../utils/ASTUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Rewrite/Core/Rewriter.h"
+#include <iostream>
+using namespace std;
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+void MathMissingParenthesesCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(binaryOperator(unless(hasParent(binaryOperator())),
+                                    hasDescendant(binaryOperator()))
+                         .bind("binOp"),
+                     this);
+}
+
+void addParantheses(const BinaryOperator *BinOp, clang::Rewriter &Rewrite,
+                    const BinaryOperator *ParentBinOp, bool &NeedToDiagnose) {
+  if (!BinOp)
+    return;
+  if (ParentBinOp != nullptr &&
+      ParentBinOp->getOpcode() != BinOp->getOpcode()) {
+    NeedToDiagnose = true;
+  }
+  clang::SourceLocation StartLoc = BinOp->getLHS()->getBeginLoc();
+  clang::SourceLocation EndLoc = BinOp->getRHS()->getEndLoc();
+  Rewrite.InsertText(StartLoc, "(");
+  Rewrite.InsertTextAfterToken(EndLoc, ")");
+  addParantheses(dyn_cast<BinaryOperator>(BinOp->getLHS()), Rewrite, BinOp,
+                 NeedToDiagnose);
+  addParantheses(dyn_cast<BinaryOperator>(BinOp->getRHS()), Rewrite, BinOp,
+                 NeedToDiagnose);
----------------
5chmidti wrote:

When you add `->IgnoreImpCasts()` to `getLHS()` and `getRHS()`, then implicit conversions will be ignored and code like `int a = 1U + 2 * 3;` will also be detected (please add tests for mixed types).

https://github.com/llvm/llvm-project/pull/84481