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Date: Fri, 19 Mar 2021 15:52:54 +0100
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To: Marco Pivetta <ocramius@gmail.com>
Cc: Matthew Brown <matthewmatthew@gmail.com>, Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] noreturn type
From: nikita.ppv@gmail.com (Nikita Popov)

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On Fri, Mar 19, 2021 at 3:45 PM Marco Pivetta <ocramius@gmail.com> wrote:

> Hey Nikita,
>
> On Fri, Mar 19, 2021, 14:35 Nikita Popov <nikita.ppv@gmail.com> wrote:
>
>>
>> Is it allowed to declare a noreturn function that returns by reference?
>>
>> function &foo(): noreturn {}
>>
>
> Given that `noreturn` means it should throw, loop forever or exit, how
> would a by-ref usage be applied/useful?
>
> Or is it a hint at a missing test?
>

Mainly a hint for missing spec ;)

Context is that we're considering to deprecate by-ref void return (
https://wiki.php.net/rfc/deprecations_php_8_1#return_by_reference_with_void_type),
so it would make sense to me to prohibit this for noreturn from the start.

However, I could also see an argument for why allowing it may be useful due
to variance considerations. It would allow you to write something like this:

<?php
class A {
    public function &test(): int { ... }
}
class B extends A {
    public function &test(): noreturn { throw new Exception; }
}

While dropping the by-ref return on B::test() would be forbidden by
variance (and I don't think we'd want to add more special rules here, like
ignoring ref-return variance for noreturn functions).

Regards,
Nikita

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