Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:92759
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.192.194 as permitted sender)
MIME-Version: 1.0
Date: Mon, 25 Apr 2016 17:37:05 -0600
Message-ID: <CAFMT4Npe8hJ1HOeJB3kfN11fnmyzRGi6znuR=Ay8kHds-ogSXQ@mail.gmail.com>
To: internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: [RFC] Patch for Union and Intersection Types
From: morrison.levi@gmail.com (Levi Morrison)

Internals,

Joe Watkins and Bob Weinand have worked out a [proof-of-concept patch
for union types][1]. Please go download it and experiment with it.

A few things to note:

  * This patch includes intersection types. However, a type expression
must be either a union type or an intersection type; it doesn't
support both such as `Array | (Countable & Traversable)`.
  * This patch adds `null`, `true` and `false` for type declarations.
  * This patch includes conversion rules for weak types.
  * It does not have short-hand for unions with null (`?Foo` being `Foo | Null`)

These features (or omitted ones) are not necessarily what will be
voted on. Rather this patch allows us to experiment with these
features in code. This experience should be helpful for us to solidify
how we actually feel about these features.

I especially would like people to try out the conversion rules for
scalar types as it has been a point of discussion.

  [1]: https://github.com/php/php-src/pull/1887