[clang-tools-extra] Add clang-tidy check to suggest replacement of conditional statement with std::min/std::max (PR #77816)

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,97 @@
+//===--- UseStdMinMaxCheck.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 "UseStdMinMaxCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Preprocessor.h"
+#include <optional>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+void UseStdMinMaxCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      ifStmt(
+          has(binaryOperator(
+              anyOf(hasOperatorName("<"), hasOperatorName(">"),
+                    hasOperatorName("<="), hasOperatorName(">=")),
+              hasLHS(expr().bind("lhsVar1")), hasRHS(expr().bind("rhsVar1")))),
+          hasThen(stmt(binaryOperator(hasOperatorName("="),
+                                      hasLHS(expr().bind("lhsVar2")),
+                                      hasRHS(expr().bind("rhsVar2"))))))
+          .bind("ifStmt"),
+      this);
+}
+
+void UseStdMinMaxCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *lhsVar1 = Result.Nodes.getNodeAs<Expr>("lhsVar1");
+  const auto *rhsVar1 = Result.Nodes.getNodeAs<Expr>("rhsVar1");
+  const auto *lhsVar2 = Result.Nodes.getNodeAs<Expr>("lhsVar2");
+  const auto *rhsVar2 = Result.Nodes.getNodeAs<Expr>("rhsVar2");
+  const auto *ifStmt = Result.Nodes.getNodeAs<IfStmt>("ifStmt");
+  auto &Context = *Result.Context;
+
+  if (!lhsVar1 || !rhsVar1 || !lhsVar2 || !rhsVar2 || !ifStmt)
+    return;
+
+  const auto *binaryOp = dyn_cast<BinaryOperator>(ifStmt->getCond());
+  if (!binaryOp)
+    return;
+
+  SourceLocation ifLocation = ifStmt->getIfLoc();
+  SourceLocation thenLocation = ifStmt->getEndLoc();
+  auto lhsVar1Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(lhsVar1->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  auto lhsVar2Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(lhsVar2->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  auto rhsVar1Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(rhsVar1->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  auto rhsVar2Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(rhsVar2->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  if (binaryOp->getOpcode() == BO_LT) {
+    if (lhsVar1Str == lhsVar2Str && rhsVar1Str == rhsVar2Str) {
+      diag(ifStmt->getIfLoc(), "use `std::max` instead of `<`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::max(" +
+                                              lhsVar1Str.str() + ", " +
+                                              rhsVar1Str.str() + ")");
+    } else if (lhsVar1Str == rhsVar2Str && rhsVar1Str == lhsVar2Str) {
----------------
PiotrZSL wrote:

probably better would be to compare expressions (with clang::tidy::utils::areStatementsIdentical) instead of strings, and this could be done on matcher level with isStatementIdenticalToBoundNode matcher.
Simply because there can be some differences with formatting (new lines) or spaces, and strings wont be equal.

https://github.com/llvm/llvm-project/pull/77816