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Date: Tue, 20 Jul 2021 21:19:43 +0200
Message-ID: <CADK1yXLvdYKe0wraNpnJFY8O7Cbpvaoptyb552pK6UFRr=GeWw@mail.gmail.com>
To: Niklas Keller <me@kelunik.com>
Cc: Nikita Popov <nikita.ppv@gmail.com>, "G. P. B." <george.banyard@gmail.com>, 
	Guilliam Xavier <guilliam.xavier@gmail.com>, Dan Ackroyd <Danack@basereality.com>, 
	Nicolas Grekas <nicolas.grekas@gmail.com>, PHP Internals List <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="00000000000059712805c792f0b5"
Subject: Re: [PHP-DEV] intersection types and null for defaults, properties
 and return types
From: deleugyn@gmail.com (Deleu)

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On Tue, Jul 20, 2021, 20:35 Niklas Keller <me@kelunik.com> wrote:

> >
> > > > > nicolas-grekas wrote on the PR:
> > > > > > ?X&Y cannot be confused with
> > > > >
> > > > > It confused me. A compiler might understand it, but as a human I
> have
> > > > > trouble understanding it.
> >
>
> I think ?X&Y would be a pretty poor syntax choice, as it's ambiguous as
> many others said: (X|null)&(Y) vs. (X&Y)|null.
>
> What hasn't been proposed, yet, is ?X&?Y, so requiring either all or none
> of the types being nullable.
>
> Best,
> Niklas
>


From the look of the syntax I would prefer it not to land on 8.1 at all,
which gives us another year to think of any syntax less aggressive to the
eyes.

One of the things I loved about the Pure Intersection RFC was that it
avoided the discussion around parenthesis on type declaration altogether.
Maybe if a type alias is proposed before mingling Union and Intersection,
then it's less of an aggressive syntax.

Type T = (X&Y)|Z|null

I don't know if anyone has offered this before, but if making an exception
for nullable Intersection is on the table, what about putting the null sign
at the end?

X&Y&Z?

It doesn't seem ambiguous because PHP defines ?X as nullable X. It doesn't
seem obvious what the ? is doing at the end but at least it doesn't seem
ambiguous.

>

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