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To: Robert Landers <landers.robert@gmail.com>
Cc: internals <internals@lists.php.net>, mark@demon-angel.eu
Date: Mon, 13 Jun 2022 14:12:44 +0200
Message-ID: <5211542.0VBMTVartN@arnaud-t490>
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References: <2b35605f-8da8-46b1-aec3-00bd1bfe47fd@www.fastmail.com> <827956617.0ifERbkFSE@arnaud-t490> <CAPzBOBM4CKv7WLu2r6=DX20Ev0-tf0OdsxufxxPzt7RoWtAneg@mail.gmail.com>
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Subject: Re: [PHP-DEV] [RFC] Short Closures 2, aka auto-capture take 3
From: arnaud.lb@gmail.com (Arnaud Le Blanc)

On lundi 13 juin 2022 12:28:17 CEST Robert Landers wrote:
> From a maintainer and code review aspect, I prefer the longer syntax
> because it is 100% clear on which variables are being closed over and
> utilized in the anonymous function. fn($x) => $x + $y is pretty clear
> that $y is being pulled in from an outer scope but if you start
> getting into longer ones, it can get non-obvious pretty quickly...
> 
> $func = fn($x) {
>   $y[] = $x;
>   // do some stuff
>   return $y;
> }
> 
> If $y is pulled from the outside scope, it may or may not be
> intentional but hopefully, it is an array. If anyone uses the name $y
> outside the lambda, this code may subtly break.

This is true for any function that uses the array-append operator on an 
undefined variable.