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

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,112 @@
+//===--- 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 "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+void MathMissingParenthesesCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(binaryOperator(unless(hasParent(binaryOperator())),
+                                    unless(allOf(hasOperatorName("&&"),
+                                                 hasOperatorName("||"))),
+                                    hasDescendant(binaryOperator()))
+                         .bind("binOp"),
+                     this);
+}
+
+static int getPrecedence(const BinaryOperator *BinOp) {
+  if (!BinOp)
+    return 0;
+  switch (BinOp->getOpcode()) {
+  case BO_Mul:
+  case BO_Div:
+  case BO_Rem:
+    return 5;
+  case BO_Add:
+  case BO_Sub:
+    return 4;
+  case BO_And:
+    return 3;
+  case BO_Xor:
+    return 2;
+  case BO_Or:
+    return 1;
+  default:
+    return 0;
+  }
+}
+static bool addParantheses(
+    const BinaryOperator *BinOp, const BinaryOperator *ParentBinOp,
+    std::vector<
+        std::pair<clang::SourceRange, std::pair<const clang::BinaryOperator *,
+                                                const clang::BinaryOperator *>>>
+        &Insertions,
+    const clang::SourceManager &SM, const clang::LangOptions &LangOpts) {
+  bool NeedToDiagnose = false;
+  if (!BinOp)
+    return NeedToDiagnose;
+
+  if (ParentBinOp != nullptr &&
+      getPrecedence(BinOp) != getPrecedence(ParentBinOp)) {
+    NeedToDiagnose = true;
+    const clang::SourceLocation StartLoc = BinOp->getBeginLoc();
+    clang::SourceLocation EndLoc =
+        clang::Lexer::getLocForEndOfToken(BinOp->getEndLoc(), 0, SM, LangOpts);
+    Insertions.push_back(
+        {clang::SourceRange(StartLoc, EndLoc), {BinOp, ParentBinOp}});
+  }
+
+  NeedToDiagnose |= addParantheses(
+      dyn_cast<BinaryOperator>(BinOp->getLHS()->IgnoreImpCasts()), BinOp,
+      Insertions, SM, LangOpts);
+  NeedToDiagnose |= addParantheses(
+      dyn_cast<BinaryOperator>(BinOp->getRHS()->IgnoreImpCasts()), BinOp,
+      Insertions, SM, LangOpts);
+  return NeedToDiagnose;
+}
+
+void MathMissingParenthesesCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *BinOp = Result.Nodes.getNodeAs<BinaryOperator>("binOp");
+  std::vector<
+      std::pair<clang::SourceRange, std::pair<const clang::BinaryOperator *,
+                                              const clang::BinaryOperator *>>>
+      Insertions;
+  const clang::SourceLocation StartLoc = BinOp->getBeginLoc();
+  const SourceManager &SM = *Result.SourceManager;
+  const clang::LangOptions &LO = Result.Context->getLangOpts();
+
+  if (addParantheses(BinOp, nullptr, Insertions, SM, LO)) {
+    for (const auto &Insertion : Insertions) {
+      const clang::BinaryOperator *BinOp1 = Insertion.second.first;
+      const clang::BinaryOperator *BinOp2 = Insertion.second.second;
+
+      int Precedence1 = getPrecedence(BinOp1);
+      int Precedence2 = getPrecedence(BinOp2);
+
+      auto Diag = diag(Insertion.first.getBegin(),
+                       "'%0' has higher precedence than '%1'; add parentheses "
+                       "to make the precedence of operations explicit")
----------------
PiotrZSL wrote:

were thinking about this, I thing this will be better:
`'%0' has higher precedence than '%1'; add parentheses to explicitly specify the order of operations`

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