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

[Piotr Zegar via cfe-commits]

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@@ -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);
+}
+
+void MathMissingParenthesesCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *BinOp = Result.Nodes.getNodeAs<BinaryOperator>("binOp");
+  if (!BinOp)
+    return;
+  clang::SourceManager &SM = *Result.SourceManager;
+  clang::LangOptions LO = Result.Context->getLangOpts();
+  Rewriter Rewrite(SM, LO);
+  bool NeedToDiagnose = false;
+  addParantheses(BinOp, Rewrite, nullptr, NeedToDiagnose);
+  clang::SourceLocation StartLoc = BinOp->getLHS()->getBeginLoc();
+  clang::SourceLocation EndLoc =
+      BinOp->getRHS()->getEndLoc().getLocWithOffset(1);
+  clang::SourceRange range(StartLoc, EndLoc);
+  std::string NewExpression = Rewrite.getRewrittenText(range);
+  if (NeedToDiagnose) {
+    diag(StartLoc, "add parantheses to clarify the precedence of operations")
+        << FixItHint::CreateReplacement(range, NewExpression);
----------------
PiotrZSL wrote:

Do not use CreateReplacement, instead just use CreateInsertion multiple times.
Simply save info where '(' and ')' has to be added, and then insert them all to Diag at once in loop.
In that way there will be less conflicts between checks, when fixes from multiple checks are added at once.

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