[clang] [clang] NFC: Refactor UnsignedOrNone into SmallOptional<T> with enum support (PR #191828)

[Younan Zhang via cfe-commits]

================
@@ -0,0 +1,79 @@
+//===- UnsignedOrNone.h - simple optional index-----*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Defines clang::UnsignedOrNone.
----------------
zyn0217 wrote:

This should be updated too

https://github.com/llvm/llvm-project/pull/191828