[clang-tools-extra] Add check 'modernize-use-enum-class' (PR #138282)

[Aaron Puchert via cfe-commits]

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@@ -0,0 +1,34 @@
+//===--- UseEnumClassCheck.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 "UseEnumClassCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+void UseEnumClassCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      traverse(TK_AsIs,
+               enumDecl(unless(isScoped()), unless(hasParent(recordDecl()))))
----------------
aaronpuchert wrote:

An option sounds good to me. There are two aspects of `enum class` that make it interesting: one is the conversion aspect and another is the scope. I guess the guidelines don't mention the scope because prior to C++11 you could wrap an enumeration in a record type, as it is allowed here. For those that mainly care about the scope, the option seems like a better way than an entirely different check. (Not even considering the question where we might put that.)

https://github.com/llvm/llvm-project/pull/138282