Backport Ref<T> to 3.26 (#109)

* Backport Ref<T> to 3.26

* Remove hhvm nightly from tests

HHVM 4.41-dev hurt itself in its confusion.

* Update .travis.yml

* Test using Docker

* Install PHP 7.2

Some of out PHP composer packages need a newer PHP

* Require ubuntu bionic to upgrade PHP

We need a PHP version of 7.1 or greater.
Testing on something newer than trusty might help.

* The the travis contant TRAVIS_PHP_VERSION

* Define PHP 7.1 and run composer using hhvm

* Revert define PHP 7.1

* Fix composer path

* HackTest didn't exist in HHVM 3.26 days

.travis.sh

@@ -1,12 +1,27 @@
 #!/bin/sh
 set -ex
+apt update -y
+DEBIAN_FRONTEND=noninteractive apt install -y php-cli zip unzip
 hhvm --version
+php --version
+if [ ! -e .git/refs/heads/master ]; then
+  # - Travis clones with `--branch`, then moves to a detached HEAD state
+  # - if we're on a detached HEAD, Composer uses master to resolve branch
+  #   aliases.
+  # So, create the master branch :p
+  git branch master HEAD
+fi
 
-composer install
+(
+  cd $(mktemp -d)
+  curl https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
+)
+if (hhvm --version | grep -q -- -dev); then
+  # Doesn't exist in master, but keep it here so that we can test release
+  # branches on nightlies too
+  rm -f composer.lock
+fi
+hhvm /usr/local/bin/composer install
 
 hh_client
-
-hhvm vendor/bin/phpunit tests/
-
-echo > .hhconfig
-hh_server --check $(pwd)
+hhvm vendor/bin/phpunit tests/

.travis.yml

@@ -1,11 +1,13 @@
-language: php
-php:
- - hhvm
- - hhvm-nightly
-matrix:
-  allow_failures:
-  - php: hhvm
+sudo: required
+language: generic
+services: docker
+env:
+- HHVM_VERSION=3.26.3
+install:
+- docker pull hhvm/hhvm:$HHVM_VERSION
 script:
- - ./.travis.sh
+- docker run --rm -w /var/source -v $(pwd):/var/source hhvm/hhvm:$HHVM_VERSION ./.travis.sh
 notifications:
   webhooks: https://code.facebook.com/travis/webhook/
+  slack:
+    secure: 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

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) {}
+}