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Date: Thu, 16 Jun 2022 08:54:23 +0900
Message-ID: <CAH19jWhZ9WQFub5J4eDpYCdV1FwmuL0vtqVcojii8RLDpv60DA@mail.gmail.com>
To: =?UTF-8?Q?Alexandru_P=C4=83tr=C4=83nescu?= <drealecs@gmail.com>
Cc: Ilija Tovilo <tovilo.ilija@gmail.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC][Under discussion] Fetch properties in const expressions
From: sji@sj-i.dev (shinji igarashi)

Hello, Ilija, Alex,

> Yes, that would work fine.

Thanks for the answer!

I am not opposed to this behavior, but it might be better to mention
it in the RFC.

Unlike Enums, an object in a constant can have mutable state, so the
result depends on when the constant expression is executed.

If it is difficult or doesn't have the benefit to determine the timing, it would
be better to clearly state that the timing of the execution of such constant
expression is undefined for now.

It is also an understandable behavior to prohibit the use of normal
objects in the property fetching in constant expressions because of the
difference in mutability between Enum and other objects.

> That would mean it would not be supported for
> - class constant initializers
> - instance property initializers
> - static property initializers

The new in initializers RFC doesn't explicitly mention the fact that
it allows class constants having objects via global constant, but
it's already doable in PHP 8.1.

class A {public int $i = 42;}
const BARE_CONSTANT = new A;
class B {
    const ClassConstant = BARE_CONSTANT;
}

echo B::ClassConstant->i;

Thanks!

--
Shinji Igarashi