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Date: Wed, 4 Sep 2019 12:54:31 +0100
Message-ID: <CA+kxMuTVxLYHkDf2b+qm7f2cfOG=fMBppcCxAW4X+iF4-W_pJw@mail.gmail.com>
To: Nicolas Grekas <nicolas.grekas+php@gmail.com>, arnold.adaniels.nl@gmail.com
Cc: Nikita Popov <nikita.ppv@gmail.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Union Types v2
From: Danack@basereality.com (Dan Ackroyd)

On Wed, 4 Sep 2019 at 10:59, Nicolas Grekas
<nicolas.grekas+php@gmail.com> wrote:

> we use "@return $this" quite often. On the implementation side, I'd
> suggest enforcing this at compile time only (enforce all return points are
> explicit, and written as "return $this"

That's doing a deeper level of thing than a type system normal does.

It's enforcing the internal behaviour of a function, rather than just
defining the type of the parameter that is returned.


> if we were to use "?int" instead, the engine would force the
> community to add "return null;"

That sounds like a bug to me. The fact that null is returned by any
function that lacks an explicit return value, is well-defined, and one
of the most underrated aspects of PHP imo.


Arnold Daniels wrote:
> Instead of using `__toString` as type maybe it's better to introduce
> a `Stringable` interface,

Although casting things to string is probably the most common use
case, if you're going to think about an RFC along those lines,
covering all of the scalars would probably be a good idea, as that
would allow people to use specific types for values, that can then be
passed easily to functions that expect a scalar.

function setRetryLimit(int $maxRetries) {...}

class ImageUploadRetryLimit extends int {...}

function processImage(ImageUploadRetryLimit $iurl, ....) {
    ...
    setRetryLimit($iurl);
    ...
}

That type* of stuff is completely possible currently in PHP, it's just
that it's a bit painful to both write and read.

cheers
Dan
Ack


*intended