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Date: Mon, 13 Jun 2022 12:28:17 +0200
Message-ID: <CAPzBOBM4CKv7WLu2r6=DX20Ev0-tf0OdsxufxxPzt7RoWtAneg@mail.gmail.com>
To: Arnaud Le Blanc <arnaud.lb@gmail.com>
Cc: internals <internals@lists.php.net>, mark@demon-angel.eu
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Subject: Re: [PHP-DEV] [RFC] Short Closures 2, aka auto-capture take 3
From: landers.robert@gmail.com (Robert Landers)

On Mon, Jun 13, 2022 at 11:36 AM Arnaud Le Blanc <arnaud.lb@gmail.com> wrote:
>
> On dimanche 12 juin 2022 19:54:06 CEST Mark Baker wrote:
> > Did many of those closures use "pass by reference" in the use clause,
> > because that's one real differentiator between traditional closures and
> > short lambdas. There's also the fact that use values are bound at the
> > point where the closure is defined, not where it's called (if they even
> > exist at all at that point), although that's probably more difficult to
> > determine.
>
> Please note that auto-capture binds variables at function declaration. This is
> the case in Arrow Functions, and is inherited by this RFC.
>
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>

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.

That being said, I'd love this RFC broken into two RFCs, one for
generic auto-capturing and one for multi-line fn functions (just to
reduce some typing when refactoring). There are times when
auto-capturing can be useful for all lambdas, especially when writing
some custom middleware.