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Date: Thu, 1 Apr 2021 12:03:03 -0700
Message-ID: <CALfTnfX9Wmfhh1i_GxUrHpZYCzS83UWOkVncEwDeY1Z+qSKq=Q@mail.gmail.com>
To: Bruce Weirdan <weirdan@gmail.com>
Cc: Andreas Leathley <a.leathley@gmx.net>, PHP Internals <internals@lists.php.net>, 
	Benjamin Eberlei <kontakt@beberlei.de>
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Subject: Re: [PHP-DEV] [VOTE] noreturn type
From: ondrej@mirtes.cz (=?UTF-8?Q?Ond=C5=99ej_Mirtes?=)

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On 1. 4. 2021 19:24:35, Bruce Weirdan <weirdan@gmail.com> wrote:

> Since `throw` is an expression (since PHP 8.0,
> https://wiki.php.net/rfc/throw_expression), it must have a type for its
> result,
> as any expression has a type. And it's result is exactly `noreturn` (or
> `never`, as this option seems to be preferred
> judging by current vote results), because `throw` never returns.
>
> It's quite natural to extend that to function calls that never return as
> well. And then it makes sense to declare that type
> as a part of function signature like you can do with other types.
>
> --
>  Best regards,
>      Bruce Weirdan                                     mailto:
> weirdan@gmail.com
>

Yes, this works very well in the typesystem. For example if we define the
type of the match expression as a union of all its arms, then the arm that
always throws or contains exit() has the noreturn/never type, which is
thrown away in a union (int|string|never can be normalized to int|string).

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