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

[Julian Schmidt via cfe-commits]

================
@@ -0,0 +1,132 @@
+//===--- 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 "../utils/ASTUtils.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 {
+
+UseStdMinMaxCheck::UseStdMinMaxCheck(StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IncludeInserter(Options.getLocalOrGlobal("IncludeStyle",
+                                               utils::IncludeSorter::IS_LLVM),
+                      areDiagsSelfContained()),
+      AlgorithmHeader(Options.get("AlgorithmHeader", "<algorithm>")) {}
+
+void UseStdMinMaxCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeStyle", IncludeInserter.getStyle());
+}
+
+void UseStdMinMaxCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      ifStmt(
+          has(binaryOperator(
+              anyOf(hasOperatorName("<"), hasOperatorName(">"),
+                    hasOperatorName("<="), hasOperatorName(">=")),
+              hasLHS(expr().bind("lhsVar1")), hasRHS(expr().bind("rhsVar1")))),
+          hasThen(
+              anyOf(stmt(binaryOperator(hasOperatorName("="),
+                                        hasLHS(expr().bind("lhsVar2")),
+                                        hasRHS(expr().bind("rhsVar2")))),
+                    compoundStmt(has(binaryOperator(
+                        hasOperatorName("="), hasLHS(expr().bind("lhsVar2")),
+                        hasRHS(expr().bind("rhsVar2"))))))))
+          .bind("ifStmt"),
+      this);
+}
+
+void UseStdMinMaxCheck::registerPPCallbacks(const SourceManager &SM,
+                                            Preprocessor *PP,
+                                            Preprocessor *ModuleExpanderPP) {
+  IncludeInserter.registerPreprocessor(PP);
+}
+
+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");
----------------
5chmidti wrote:

Please run `clang-tidy --checks="-*,readability-identifier-naming" -fix -p <your-build-dir> clang-tools-extra/clang-tidy/readability/UseStdMinMaxCheck.cpp` to let clang-tidy change the variable names to `CamelCase` instead of `camelBack` (this comes from .clang-tidy file at the top of the tree).

There are a few more variables named this way inside this function.
The `IfStmt` won't be changed, maybe change the bound name to `if` and name the variable `If`?

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