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Date: Wed, 4 Jun 2025 16:54:05 +0200
User-Agent: Mozilla Thunderbird
Subject: Re: [PHP-DEV] [RFC] Transform void into an alias for null
To: "Gina P. Banyard" <internals@gpb.moe>,
 PHP internals <internals@lists.php.net>
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From: bobwei9@hotmail.com (Bob Weinand)

On 2.6.2025 18:27:51, Gina P. Banyard wrote:
> Hello internals,
>
> This is the second RFC out of a set of type system related RFCs I want to propose for PHP 8.5.
>
> The objective is to fix a weird quirk of PHP's type system, where void lives in its own type hierarchy.
> This is visible mainly in that a lack of return type is not isomorphic to a function that has a return type of mixed.
>
> Let me know what you think about it.
>
> RFC: https://wiki.php.net/rfc/void-as-null
>
> Best regards,
>
> Gina P. Banyard

I have to agree with other posters here that the distinction between 
null and void is an useful one.

In particular I'd consider the null returned by void to be incidental 
rather than intentional. I consider the return value of void functions 
"some arbitrary value". It just happens to be null.
Like every function has to return something. But returning null is not 
an intrinsic property of a void function. It's an extrinsic one. You 
observe void functions to generally return null. But that null in itself 
is meaningless.

So, my counter-proposal would be allowing covariance with void and 
allowing everything, including non-nullable types as child type of void 
functions.
I.e. effectively giving void and never the same semantics, except that 
never also indicates that it never returns.

Additionally I'd be in favour of disallowing (e.g. E_WARNING) consuming 
the return value of _direct_ calls to void functions (with the exception 
of standalone direct calls in short closures, because consuming that 
value is intrinsic rather than necessarily intentional). (Disallowing 
indirect calls would be detrimental for usage as callback.)

Bob