Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:107224
To: Nikita Popov <nikita.ppv@gmail.com>
References: <CAF+90c8EvfFPqjRJjJ3T-qTfLiWn7aZzCrGpk7R3yNFLT1qWjQ@mail.gmail.com>
 <CAF+90c8CvL3xvUpX1o2RH2Jjjj=fW5XbrLS5tkc6FdmS4cC+eQ@mail.gmail.com>
Cc: PHP internals <internals@lists.php.net>
Message-ID: <e161286a-bb7e-d789-d10a-a04e35b7f7a0@telia.com>
Date: Thu, 19 Sep 2019 01:03:30 +0200
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101
 Thunderbird/60.9.0
MIME-Version: 1.0
In-Reply-To: <CAF+90c8CvL3xvUpX1o2RH2Jjjj=fW5XbrLS5tkc6FdmS4cC+eQ@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-GB
Subject: Re: [PHP-DEV] Re: [RFC] Union Types v2
From: bjorn.x.larsson@telia.com (=?UTF-8?Q?Bj=c3=b6rn_Larsson?=)

Den 2019-09-18 kl. 15:33, skrev Nikita Popov:
> On Wed, Sep 4, 2019 at 10:26 AM Nikita Popov <nikita.ppv@gmail.com> wrote:
>
>> Hi internals,
>>
>> I'd like to start the discussion on union types again, with a new proposal:
>>
>> Pull Request: https://github.com/php/php-rfcs/pull/1
>> Rendered Proposal:
>> https://github.com/nikic/php-rfcs/blob/union-types/rfcs/0000-union-types-v2.md
>>
>> As an experiment, I'm submitting this RFC as a GitHub pull request, to
>> evaluate whether this might be a better medium for RFC proposals in the
>> future. It would be great if we could keep the discussion to the GitHub
>> pull request for the purpose of this experiment (keep in mind that you can
>> also create comments on specific lines in the proposal, not just the
>> overall discussion thread!) Of course, you can also reply to this mail
>> instead. The final vote will be held in the wiki as usual.
>>
>> Relatively to the previous proposal by Bob&Levi (
>> https://wiki.php.net/rfc/union_types), I think the main differences in
>> this proposal are:
>>   * Updated to specify interaction with new language features, like full
>> variance and property types.
>>   * Updated for the use of the ?Type syntax rather than the Type|null
>> syntax.
>>   * Only supports "false" as a pseudo-type, not "true".
>>   * Slightly simplified semantics for the coercive typing mode.
>>
>> Regards,
>> Nikita
>>
> Heads up, two weeks have passed, so this may now go to voting...
>
> I believe relative to my original draft the main change that has happened
> as a result of the discussion is the use of T1|T2|null syntax instead of
> ?(T1|T2) syntax for nullable types. ?T becomes an alias for T|null. People
> felt fairly strongly that while ?T is a nice shorthand for a common case,
> unions should use the T1|T2|null syntax that both reads better and is
> already well-established from phpdoc.
>
> I figured I should mentioned this for people who haven't been following the
> GitHub thread...
>
> Nikita


Hi Nikita,

Planned to comment on ? vs null on Github, but here it goes. Advantage
with ? syntax was in my eyes that it's clear it's not a stand-alone type or
what I should call it, but rather a "change/variant" to an existing type.

Having it stated as T1|T2|null lead it a bit in the direction of being a 
more
stand-alone type. Anyway, I'm quite happy with the proposal as it is. So
thanks for the excellent work!

r//Björn L