[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) {
+      diag(ifStmt->getIfLoc(), "use `std::min` instead of `<`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::min(" +
+                                              lhsVar1Str.str() + ", " +
+                                              rhsVar1Str.str() + ")");
+    }
+  } else if (binaryOp->getOpcode() == BO_GT) {
+    if (lhsVar1Str == lhsVar2Str && rhsVar1Str == rhsVar2Str) {
+      diag(ifStmt->getIfLoc(), "use `std::min` instead of `>`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::min(" +
+                                              lhsVar1Str.str() + ", " +
+                                              rhsVar1Str.str() + ")");
+    } else if (lhsVar1Str == rhsVar2Str && rhsVar1Str == lhsVar2Str) {
+      diag(ifStmt->getIfLoc(), "use `std::max` instead of `>`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::max(" +
+                                              lhsVar1Str.str() + ", " +
----------------
PiotrZSL wrote:

better would be to move text instead of doing a copy, to avoid conflicts between checks.

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