Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:105334
Date: Mon, 22 Apr 2019 22:08:33 +0000
To: Larry Garfield <larry@garfieldtech.com>
Cc: "internals@lists.php.net" <internals@lists.php.net>
Reply-To: azjezz <azjezz@protonmail.com>
Message-ID: <JEmT1BemUqk-eEqeoTK1FeXFDeN3Orx3kyduyrCFhABbotjP1sEcIKTUi51vgzXUWJ0M6zjWZzwiU07Rcd3jZZoDt5-VBShT54EPKJTZ4EM=@protonmail.com>
In-Reply-To: <c6e7ee21-b669-46c3-8921-d70aa1cc61f0@www.fastmail.com>
References: <CAG9XoMS3xwNEsSvFaad5ExK4o9dhrKG9yaP2enp+yRQDmpr4Ow@mail.gmail.com>
 <c6e7ee21-b669-46c3-8921-d70aa1cc61f0@www.fastmail.com>
Feedback-ID: 2QbNVvXqZX7F9J8FTDAv0u3ryua4T0_lfklxZ8hRMzvBUxf8m8U50Gi9tVWG9V2LePU31MFOrVnxPKYLJjZPXw==:Ext:ProtonMail
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PHP-DEV] Object Type Casting Reloaded
From: azjezz@protonmail.com (azjezz)

Hello, Internals.

I have been using HackLang for quite a while now and i believe they have a =
better solution for this, and it would awesome to see it in PHP, the `as` o=
perator.

see : https://docs.hhvm.com/hack/expressions-and-operators/as

---

when i see :

```
$foo =3D (Foo) $object;
```
i think that `$object` is going to be converted to an instance of `Foo`, no=
t ensure that its an instance of `Foo`.

Hack `as` operator
```
$foo =3D $object as Foo;
// or
$object as Foo;
// use `$object` now, known that its an instance of `Foo`

```

> a `TypeAssertionException` expect would be throw if `$object` is not `Foo=
`.






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 Monday, April 22, 2019 11:03 PM, Larry Garfield <larry@garfieldtech.com>=
 wrote:

> On Mon, Apr 22, 2019, at 4:47 PM, Benjamin Morel wrote:
>
> > 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
>
> Hi Ben.
>
> First thought: I'm all for easy ways to be more type-explicit, so yay on =
the concept.
>
> Second thought: That said, how many use cases for that are there other th=
an function boundaries, which we already have covered?
>
> I can think of two: foreach() loops and returns where you know the return=
 type with more specificity than the method you're calling. Example:
>
> /** @var Foo $foo *//
> foreach ($arrayOfFoo as $foo) {
> $foo->bar();
> }
>
> Example from PSR-14, in which you know the object you're getting back MUS=
T be the same one that's passed in but dispatch() has no return type:
>
> /** @var Foo $event **/
> $event =3D $dispatcher->dispatch(new Foo());
>
> The second I can see being easily handled by this syntax. The former, how=
 would that look?
>
> Third thought: Casting is the wrong name here, and feels also misleading =
as a syntax. (float)$anInt means "type coerce this thing into a float", whi=
ch cannot error. You're suggesting (Foo)$bar to mean "if this isn't already=
 a Foo, throw." That's a very different behavior semantic for the same synt=
ax. Is that a land mine? I would expect (Foo)$bar to mean "recast $bar into=
 an instance of Foo if possible, and error if not". Which... I suppose "is =
it already" is a subcase of that, but it's still not the behavior I'd expec=
t from that syntax.
>
> --Larry Garfield
>
> -------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------
>
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php