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Date: Thu, 13 Feb 2025 15:17:07 +0100
To: Eugene Sidelnyk <zsidelnik@gmail.com>
Cc: Jakob Givoni <jakob@givoni.dk>, volker@tideways-gmbh.com, PHP Internals
 <internals@lists.php.net>
Subject: Re: [PHP-DEV] Re: RFC: Marking return values as important
 (#[\NoDiscard])
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

Am 2025-02-13 09:49, schrieb Eugene Sidelnyk:
> I'm just wondering how the new attribute that defines behavior (not 
> just
> additional metadata) will fit into the rest of the system.

See my reply to Jakob: There are already several attributes that define 
behavior.

> Do you think it's reasonable to implement "non-discardability of the
> returned value" as the attribute? Maybe new keyword would be better
> solution?

Yes, we believe that implementing this as an attribute rather than a 
keyword is the right choice and the reasoning is similar to the 
`#[\Override]` attribute that was added in PHP 8.3: 
https://wiki.php.net/rfc/marking_overriden_methods#why_an_attribute_and_not_a_keyword

With the exception of error handlers, applying (or unapplying) the 
`#[\NoDiscard]` attribute will not affect how a PHP program works. It 
will just emit a new warning which when suppressed, will not affect the 
program’s behavior at all. This is different to return types, which are 
relevant due to the Liskov substitution principle and where changing the 
return type would actually result in a breaking change to the program’s 
public API.

Best regards
Tim Düsterhus