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Date: Thu, 31 Oct 2024 01:16:06 -0500
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Subject: Re: [PHP-DEV] RFC: Support Closures in constant expressions
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From: larry@garfieldtech.com ("Larry Garfield")

On Wed, Oct 30, 2024, at 3:01 AM, Tim D=C3=BCsterhus wrote:
> Hi
>
> Am 2024-10-30 05:25, schrieb Larry Garfield:
>> This seems like a good idea to me.  My only real question is why we=20
>> need to forbid short-closures.  I fully agree that capturing variable=
s=20
>> for such functions doesn't work.  What I don't understand is why that=20
>> precludes short-closures.  Is it not possible to "just" say "there's=20
>> nothing to even capture in this context, don't try"?  (There may be=20
>> technical reasons for that, but I do not know what they are and the R=
FC=20
>> doesn't say.)
>
> It would indeed require some special handling to disable the=20
> auto-capturing in the code. This would be solvable of course, but=20
> there's also semantic ambiguity, because users reasonably expect short=20
> closures to perform auto-capturing:
>
>      <?php
>
>      $foo =3D 'foo';
>
>      const Closure =3D static fn (array $bar): array =3D> [$foo, $bar];
>
>      var_dump((Closure)('bar'));
>
> If this would be legal syntax: What would you expect to be printed?
>
> Best regards
> Tim D=C3=BCsterhus

Hm.  It would never occur to me to use a function for a non-class consta=
nt in the first place, so I don't know. :-)  Frankly I can't recall the =
last time I used a non-class constant period. :-)

That said, PHP consts are already a bit squishy, and auto-capture is alw=
ays by value.  That wouldn't give us a loophole?

If it cannot reasonably be done now, but is possible, that should be lis=
ted in future scope with roughly what it would take for a follow-up to d=
o.  (And then we can argue if it should just be done now, with more info=
rmation as to how much work that is.)

--Larry Garfield