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

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,167 @@
+//===--- 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 <set>
+#include <stack>
+
+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);
+}
+static int precedenceCheck(const char op) {
+  if (op == '/' || op == '*' || op == '%')
+    return 5;
+
+  else if (op == '+' || op == '-')
+    return 4;
+
+  else if (op == '&')
+    return 3;
+  else if (op == '^')
+    return 2;
+
+  else if (op == '|')
+    return 1;
+
+  else
+    return 0;
+}
+static bool isOperand(const char c) {
+  if (c >= 'a' && c <= 'z')
+    return true;
+  else if (c >= 'A' && c <= 'Z')
+    return true;
+  else if (c >= '0' && c <= '9')
+    return true;
+  else if (c == '$')
+    return true;
+  else
+    return false;
+}
+static bool conditionForNegative(const std::string s, int i,
+                                 const std::string CurStr) {
+  if (CurStr[0] == '-') {
+    if (i == 0) {
+      return true;
+    } else {
+      while (s[i - 1] == ' ') {
+        i--;
+      }
+      if (!isOperand(s[i - 1])) {
+        return true;
+      } else {
+        return false;
+      }
+    }
+  } else {
+    return false;
+  }
+}
+static std::string getOperationOrder(std::string s, std::set<char> &Operators) {
+  std::stack<std::string> StackOne;
+  std::string TempStr = "";
+  for (int i = 0; i < s.length(); i++) {
+    std::string CurStr = "";
+    CurStr += s[i];
+    if (CurStr == " ")
+      continue;
+    else {
+      if (isOperand(CurStr[0]) || conditionForNegative(s, i, CurStr)) {
+        while (i < s.length() && (isOperand(s[i]) || s[i] == '-')) {
+          if (s[i] == '-') {
+            TempStr += "$";
+          } else {
+            TempStr += CurStr;
+          }
+          i++;
+          CurStr = s[i];
+        }
+        TempStr += " ";
+      } else if (CurStr == "(") {
+        StackOne.push("(");
+      } else if (CurStr == ")") {
+        while (StackOne.top() != "(") {
+          TempStr += StackOne.top();
+          StackOne.pop();
+        }
+        StackOne.pop();
+      } else {
+        while (!StackOne.empty() && precedenceCheck(CurStr[0]) <=
+                                        precedenceCheck((StackOne.top())[0])) {
+          TempStr += StackOne.top();
+          StackOne.pop();
+        }
+        StackOne.push(CurStr);
+      }
+    }
+  }
+  while (!StackOne.empty()) {
+    TempStr += StackOne.top();
+    StackOne.pop();
+  }
+  std::stack<std::string> StackTwo;
+  for (int i = 0; i < TempStr.length(); i++) {
+    if (TempStr[i] == ' ')
+      continue;
+    else if (isOperand(TempStr[i])) {
+      std::string CurStr = "";
+      while (i < TempStr.length() && isOperand(TempStr[i])) {
+        if (TempStr[i] == '$') {
+          CurStr += "-";
+        } else {
+          CurStr += TempStr[i];
+        }
+        i++;
+      }
+      StackTwo.push(CurStr);
+    } else {
+      std::string OperandOne = StackTwo.top();
+      StackTwo.pop();
+      std::string OperandTwo = StackTwo.top();
+      StackTwo.pop();
+      Operators.insert(TempStr[i]);
+      StackTwo.push("(" + OperandTwo + " " + TempStr[i] + " " + OperandOne +
+                    ")");
+    }
+  }
+  return StackTwo.top();
+}
+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();
+  clang::CharSourceRange Range =
+      clang::CharSourceRange::getTokenRange(BinOp->getSourceRange());
+  std::string Expression = clang::Lexer::getSourceText(Range, SM, LO).str();
----------------
PiotrZSL wrote:

there shoud be no need to getSourceText, just operate on AST, and then just use FixItHint::CreateInsertion to add missing (), with CreateReplacement fixes will conflict with other checks.

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