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Date: Tue, 23 Apr 2019 10:44:18 +0000
To: Dan Ackroyd <Danack@basereality.com>
Cc: Benjamin Morel <benjamin.morel@gmail.com>, PHP Internals <internals@lists.php.net>
Reply-To: azjezz <azjezz@protonmail.com>
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Subject: Re: [PHP-DEV] Object Type Casting Reloaded
From: azjezz@protonmail.com (azjezz)

Hello Dan,

I don' think this a problem relating to just one use case, some PHP builtin=
 functions have weird union return types, where static analysis tools would=
 warn you about the return type being `string|bool`, when you are expecting=
 `string`.

using type constrain :
```
$foo =3D substr($foo, 1, 3) as string;
// there's no need to check if `$foo` is false here.
```



Cheers,

- Saif


Sent with ProtonMail Secure Email.

=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original Me=
ssage =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90
On Tuesday, April 23, 2019 11:33 AM, Dan Ackroyd <Danack@basereality.com> w=
rote:

> HI Benjamin,
>
> Similar to the nullable casting idea, you're taking a problem caused
> by your own code/framework, and then thinking it should be solved in
> core, when a simple solution is available in user-land.
>
> If you changed what you currently have:
>
> $service =3D $diContainer->get('email.service');
>
> to also take the expected class:
>
> $service =3D $diContainer->get('email.service', EmailService::class);
>
> And then check inside your 'DI container' whether the expected type is
> returned, this solves the problem without needing new syntax.
>
> btw I'm sure you're already aware of it, but this is using a
> 'dependency injector' as a service locator. If your current DI library
> isn't powerful enough for you, rather than abusing it like this, I'd
> recommend looking at a different one, like
> https://github.com/rdlowrey/Auryn
>
> Also, similar:
>
> > By the way, this RFC is a special case of something that could be far
> > more generic. If it was possible to register callbacks to be used when
> > casting, ...
>
> Apparently this might not be possible as it's ambiguous....which is a sha=
me.
>
> cheers
> Dan
> Ack
>
> On Mon, 22 Apr 2019 at 22:47, Benjamin Morel benjamin.morel@gmail.com wro=
te:
>
> > Hi internals,
> > I'd like to revive an old discussion https://externals.io/message/67131=
 about
> > object type casting.
> > The idea would be to allow (ClassName) casting:
> >
> >     $service =3D (EmailService) $diContainer->get('email.service');
> >
> >
> > The above code would throw a TypeError if the value is not an instance =
of
> > the given class. I see the following advantages:
> >
> > -   Type safety: we can be sure that the value is of the correct type o=
r that
> >     we'll get an Error. This syntax allows to fail early if the variabl=
e
> >     happens to not be of the expected type, and avoids much more verbos=
e checks;
> >
> > -   Static analysis: IDEs and static code analysis tools can now unders=
tand
> >     the type of the variable, without having to resort to `@var` annota=
tions.
> >
> >
> > These combine into a third advantage: readability. Today's equivalent o=
f
> > the above one-liner could be:
> >
> >     /** @var EmailService $service */
> >     $service =3D $diContainer->get('email.service');
> >     if (! $service instanceof EmailService) {
> >         throw new TypeError('Expected instance of EmailService, ...');
> >     }
> >
> >
> > Which is a lot of boilerplate code that could be easily avoided by
> > introducing this new syntax.
> > Before moving forward and working on a formal RFC, I'd like to hear you=
r
> > thoughts: what's your early feeling about this? Did I miss other
> > discussions around this subject? Are there any technical issues that co=
me
> > to mind? Could this feature help the upcoming JIT compiler produce more
> > efficient machine code by knowing the type of the variable at compile t=
ime?
> > etc.
> > Note: "casting" might not be the perfect name here as what we're really
> > doing is a type check, but this reuses the type casting syntax and
> > resembles Java's object casting.
> > Thank you,
> > Ben
>
> --
>
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