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

[Julian Schmidt via cfe-commits]

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@@ -0,0 +1,97 @@
+//===--- 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(isAssignmentOperator()),
+                                    unless(isComparisonOperator()),
+                                    unless(hasAnyOperatorName("&&", "||")),
+                                    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 void addParantheses(const BinaryOperator *BinOp,
+                           const BinaryOperator *ParentBinOp,
+                           ClangTidyCheck *Check,
+                           const clang::SourceManager &SM,
+                           const clang::LangOptions &LangOpts) {
+  if (!BinOp)
+    return;
+
+  int Precedence1 = getPrecedence(BinOp);
+  int Precedence2 = getPrecedence(ParentBinOp);
+
+  if (ParentBinOp != nullptr && Precedence1 != Precedence2) {
+    const clang::SourceLocation StartLoc = BinOp->getBeginLoc();
+    const clang::SourceLocation EndLoc =
+        clang::Lexer::getLocForEndOfToken(BinOp->getEndLoc(), 0, SM, LangOpts);
+
+    auto Diag =
+        Check->diag(StartLoc,
+                    "'%0' has higher precedence than '%1'; add parentheses to "
+                    "explicitly specify the order of operations")
+        << (Precedence1 > Precedence2 ? BinOp->getOpcodeStr()
+                                      : ParentBinOp->getOpcodeStr())
+        << (Precedence1 > Precedence2 ? ParentBinOp->getOpcodeStr()
+                                      : BinOp->getOpcodeStr());
+
+    Diag << FixItHint::CreateInsertion(StartLoc, "(");
+    Diag << FixItHint::CreateInsertion(EndLoc, ")");
+    Diag << SourceRange(StartLoc, EndLoc);
----------------
5chmidti wrote:

Nit: You could stream these directly into the diagnostic, like the operator strings, and remove the `Diag` variable`.

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