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References: <7238EFA9-8BE4-48E2-B6C6-6C3E14CFA208@joshbruce.dev>
In-Reply-To: <7238EFA9-8BE4-48E2-B6C6-6C3E14CFA208@joshbruce.dev>
Date: Mon, 13 Jul 2020 12:19:28 +0200
Message-ID: <CAF+90c-ayB43unWK8x=PRmnSCv5jp7jekGwNbstmiWxLxt2fXw@mail.gmail.com>
To: Josh Bruce <josh@joshbruce.dev>
Cc: php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [CONCEPT][DISCUSSION] Allow objects to declare
 emptiness and by extension truthiness
From: nikita.ppv@gmail.com (Nikita Popov)

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On Sun, Jul 12, 2020 at 7:49 PM Josh Bruce <josh@joshbruce.dev> wrote:

> Latest version as we zero in on what this is really about:
> https://bit.ly/php-0002 <https://bit.ly/php-0002>
>
> Other threads:
>
> 1. https://externals.io/message/110879 <
> https://externals.io/message/110879>
> 2. https://externals.io/message/110881 <
> https://externals.io/message/110881>
>
> Thanks for all the feedback so far! Definitely feels like progress.


I have a really hard time understanding what is actually being proposed
here. You mention the introduction of the Emptiable interface, but not how
it influences empty() or (bool) casts. There's some examples in "Usage"
that are possibly intended to illustrate this -- I suspect that a "return
true" vs "return false" mixup has made them impossible to understand though.

Some thoughts on the general domain:

1. I don't like the idea of decoupling empty() and (bool). empty($x) is
currently the same as !$x (modulo notices), and changing that will make
PHP's already messy implicit type conversion matrix even messier.

2. Coupling boolean casts to an "emptiness" concept seems somewhat dubious
to me. That works for container structures, but what about something like
new Bigint(0)? It would be quite odd to declare an integer "empty" to make
it evaluate to false.

3. I'm generally not a fan of overloadable bool casts. We have exactly one
object with an overloaded bool cast in PHP, and that's SimpleXMLElement. As
far as I know, this has only caused issues. A big reason for that is that
using "if ($foo->bar)" is a common idiom for checking "if ($foo->bar !==
null)" -- one that works very reliably, with the exception of
SimpleXMLElement.

4. I think if ($container->isEmpty()) is much clearer than if ($container)
-- why would we want people to use the latter instead?

Regards,
Nikita

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