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Date: Thu, 16 Mar 2023 18:59:35 +0100
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To: Rowan Tommins <rowan.collins@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="000000000000e2a49105f7083985"
Subject: Re: [PHP-DEV] Brainstorming idea: inline syntax for lexical
 (captured) variables
From: nicolas.grekas+php@gmail.com (Nicolas Grekas)

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> > To overcome the issues spotted in the thread, what about doing some sort
> > of CPP instead of autocapture?
> >
> > new class (...$arguments) use ($outer) extends Foo {
> >     public function getIt() {
> >         return $this->outer;
> >     }
> > }
> >
> > This would be the equivalent of this:
> >
> > new class ($outer, ...$arguments) extends Foo {
> >     public function __construct(public mixed $outer, ...$arguments) {
> >         parent::__construct(...$arguments);
> >     }
> >      public function getIt() {
> >          return $this->outer;
> >     }
> > }
> >
>
>
> I was actually just thinking about exactly that approach, and wondering it
> would be possible to do it entirely as an AST rewrite.
>
> My only uncertainty so far is what to do with an actual constructor in the
> class, like this:
>
> new class($custom) use ($captured) {
>     public function __construct($custom) {
>          // Duplicate definition error?
>          // Silently renamed and called from the generated constructor?
>          // Merged into the body after the generated lines?
>     }
> }
>
> Forbidding it wouldn't be the worst restriction, but if there was some
> per-instance setup logic needed, not being able to write a constructor body
> might be a pain.
>

We could define the "use" as declaring + setting the properties before the
constructor is called, if any.
But I'm also fine making both constructs conflict: when there is a
constructor, the boilerplate saved by the "use" becomes really low.
No strong opinion either. There could be other factors to consider.



> > And we could also allow this for better type expressivity:
> > new class (...$arguments) use (private int $outer) extends Foo {
> > // ...
> > }
> >
>
>
> I was going to suggest an "as" clause, similar to traits, which would also
> allow naming the property differently from the source variable:
>
> $foo = 42;
> $name = 'Bob';
> $class = new class use ($foo as private int $counter, $name as readonly
> string) {}
>

I like that!

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