From 65d70d79258773f837929ecb749f220ebe142421 Mon Sep 17 00:00:00 2001
From: Lexidor Digital <31805625+lexidor@users.noreply.github.com>
Date: Tue, 21 Jan 2020 22:40:00 +0100
Subject: [PATCH] Backport Ref<T> to 4.5 (#116)

---
 src/Ref.php | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)
 create mode 100644 src/Ref.php

diff --git a/src/Ref.php b/src/Ref.php
new file mode 100644
index 00000000..06368c4c
--- /dev/null
+++ b/src/Ref.php
@@ -0,0 +1,28 @@
+<?hh // strict
+/*
+ *  Copyright (c) 2004-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the MIT license found in the
+ *  LICENSE file in the root directory of this source tree.
+ *
+ */
+
+namespace HH\Lib;
+
+/** Wrapper class for getting object (byref) semantics for a value type.
+ *
+ * This is especially useful for mutating values outside of a lambda's scope.
+ *
+ * In general, it's preferable to refactor to use return values or `inout`
+ * parameters instead of using this class - however, a `Ref` of a Hack array
+ * is generally preferable to a Hack collection - e.g. prefer `Ref<vec<T>>`
+ * over `Vector<T>`.
+ *
+ * `C\reduce()` and `C\reduce_with_key()` can also be used in some situations
+ * to avoid this class.
+ */
+final class Ref<T> {
+  <<__RxShallow>>
+  public function __construct(public T $value) {}
+}