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Date: Thu, 30 Jan 2025 16:50:30 +0100
To: Rob Landers <rob@bottled.codes>
Cc: Volker Dusch <volker@tideways-gmbh.com>, php internals
 <internals@lists.php.net>
Subject: Re: [PHP-DEV] RFC: Marking return values as important (#[\NoDiscard])
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 <3f170549-cfd6-441e-b892-cf51d726dbe8@bastelstu.be>
 <3b4d9be8-9255-44ab-95c5-ea3045212cf4@app.fastmail.com>
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

Am 2025-01-29 21:16, schrieb Rob Landers:
> I understand what you are saying, but I can also just remove the 
> warning via:
> 
> $_ = outer;

Please note that `$_` is a regular variable and thus will increase the 
lifetimes of returned objects (and arrays that can contain objects), 
which might or might not be observable when implementing `__destruct()`. 
Also note that OPcache will actually optimize away dead stores if it can 
guarantee that the difference is not observable (i.e. if it knows that 
the function never returns an object and if `get_defined_vars()` is not 
called).

Of course it would be possible to exclude `$_` from this dead-store 
optimization with PHP 8.5+ to allow for a smoother migration for 
libraries that require cross-version compatibility.

We nevertheless wanted to offer an alternative that might be less 
confusing than a “special variable” that might also conflict with 
diagnostics like unused variable detection.

> […] It also happens to make the diffs more natural looking when and if 
> the return value gets used during a code review. […]

Can you clarify what you mean by “more natural looking”?

Best regards
Tim Düsterhus