--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/llvm/lib/Support/Optional.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,14 @@
+//===- Optional.cpp - Optional values ---------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/Support/raw_ostream.h"
+
+llvm::raw_ostream &llvm::operator<<(raw_ostream &OS, NoneType) {
+  return OS << "None";
+}