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Date: Thu, 30 Jun 2022 18:29:44 +0200
Message-ID: <CAC5V6gjk6T_XupP8aRr0TYEH9BCoaEJUr737St5c4YKUb02O5Q@mail.gmail.com>
To: Arnaud Le Blanc <arnaud.lb@gmail.com>
Cc: internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Short Closures 2, aka auto-capture take 3
From: guilliam.xavier@gmail.com (Guilliam Xavier)

On Thu, Jun 30, 2022 at 5:57 PM Arnaud Le Blanc <arnaud.lb@gmail.com> wrote:
>
> Hi,
>
> On jeudi 30 juin 2022 16:18:44 CEST Robert Landers wrote:
> > Are
> > optimizations going to be applied to single-line arrow functions (I
> > didn't see that in the RFC, but I admittedly didn't look that hard and
> > I vaguely remember reading something about it in one of these
> > threads)? If so, it will probably change some behaviors in existing
> > applications if they were relying on it. Perhaps static analysis tools
> > can detect this and inform the developer.
>
> It is not planned to change the behavior of arrow functions in this RFC. This
> optimization is less important for arrow functions because they don't usually
> assign variables.

Ah? Sorry, I had interpreted
https://github.com/php/php-src/pull/8330/files#diff-85701127596aca0e597bd7961b5d59cdde4f6bb3e2a109a22be859ab7568b4d2R7318-R7320
as "capture the *minimal* set of variables for *both* arrow functions
and short closures", but I was wrong?

I don't see a test like this:

```php
class C {
    public function __destruct() { echo 'destructed', PHP_EOL; }
}
$x = new C();
$fn = fn ($a, $b) => (($x = $a ** 2) + ($y = $b ** 2)) * ($x - $y);
echo '- unsetting $x', PHP_EOL;
unset($x);
echo '- calling $fn', PHP_EOL;
var_dump($fn(3, 2));
echo '- unsetting $fn', PHP_EOL;
unset($fn);
echo '- DONE.', PHP_EOL;
```

with current output (https://3v4l.org/ve3BL#v8.1.7):

```
- unsetting $x
- calling $fn
int(65)
- unsetting $fn
destructed
- DONE.
```

where the optimization would make the "destructed" line move up to
just after "- unsetting $x"

-- 
Guilliam Xavier