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Date: Fri, 07 Jun 2024 18:30:18 +0000
To: "php internals" <internals@lists.php.net>
Subject: Re: [PHP-DEV] RFC proposal : "new" keyword shorthand
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From: larry@garfieldtech.com ("Larry Garfield")

On Fri, Jun 7, 2024, at 5:56 PM, ericmann@php.net wrote:

>> Instead of ~ (which reminds me of the pendulum of symbols to written =
to symbols and back again every 10ish years; =E2=80=9Cor=E2=80=9D vs =E2=
=80=9C||=E2=80=9D), why not make a shorthand way to write a function tha=
t calls a constructor (kinda sorta like C# extension methods)? Something=
 kinda like:
>>=20
>> class MyClass implements Invocable {
>>   public function __construct($i) {}
>> }
>>=20
>> MyClass($i);
>>=20
>> Where the Invocable interface defines a function of the same class na=
me in the namespace that is an alias for a new objects and forwards args=
 to the constructor. This could be quite handy for value objects.
>>=20
>> I=E2=80=99m not necessarily a fan of magic or symbols, but just tossi=
ng it out there to spark ideas.=20
>>=20
>> =E2=80=94 Rob
> --
>
> I'm not a fan of using ~ for this shorthand, due to the same issues=20
> that have been brought up elsewhere (i.e. it already has meaning). But=20
> the idea of a new interface auto-defining a function of the same name=20
> is attractive. It's something I've done manually to mirror code in PHP=20
> from other implementations existing in Scala leveraging case classes.
>
> https://docs.scala-lang.org/tour/case-classes.html for anyone=20
> unfamiliar with the construct:
>
> ```
> case class Book(isbn: String)
>
> val frankenstein =3D Book("978-0486282114")
> ```
>
> Doing something like this in PHP is a bit more ... verbose today:
>
> ```
> class Book
> {
>     public function __construct(public string $isbn) {}
> }
>
> function Book(string $isbn): Book
> {
>     return new Book($isbn);
> }
>
> $frankenstein =3D Book("978-0486282114")
> ```
>
> That's a lot of boilerplate for the shorthand to not require a `new`=20
> keyword. Which is to say, I both agree in principle with the RFC and=20
> think this would add value (particularly if I could extend the default=20
> behavior of this kind of interface to support immutability, comparison=
,=20
> etc similar to Scala case classes). I'm just not a fan of the current =
~=20
> proposal.
>
> ~Eric

The issue with auto-generating a function constructor for a class is tha=
t we still don't have function autoloading.  Which means this:

// Point.php

#[MakeFactoryFunction] (or whatever)
class Point {
  public function __construct(public int $x, public int $y) {}
}

// index.php

$p =3D Point(4, 5);

will look for a function named "Point", not find one defined yet, and fa=
tal. =20

If we had function autoloading, that would work, assuming a reasonable g=
eneric autoloader for that case could be written.  Who was it that's bee=
n talking about that for a while? :-)

Or if we had some marker to indicate "this function call is a wrapper fo=
r a class so autoload it like a class", that could then trigger the clas=
s autoloader.  But... that's basically what the original ~ proposal is, =
in the end.  Though I agree that ~ is not a great symbol for it.  PHP ha=
s, sadly, run out of unused symbols.  (I've run into this a couple of ti=
mes now.)

--Larry Garfield