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Date: Wed, 26 Jun 2013 15:35:47 +0200
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To: Patrick ALLAERT <patrickallaert@php.net>
Cc: Maxwell <Max@maxvandervelde.com>, Sherif Ramadan <theanomaly.is@gmail.com>, 
	Florin Patan <florinpatan@gmail.com>, "internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Request for comments - new PHP feature: return typing
From: jpauli@php.net (Julien Pauli)

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On Wed, Jun 26, 2013 at 2:58 PM, Patrick ALLAERT <patrickallaert@php.net>wrote:

> 2013/6/26 Maxwell <Max@maxvandervelde.com>:
> > Sherif,
> > I have to disagree with you on this in the same way that we have type
> hints
> > for input variables on methods, this could also be useful.
> > Consider an interface with a getter method defined. As it stands now in
> > php, they're not entirely useful, since you can't define what type of
> > object your expecting from the implementer. That greatly reduces the
> > functionality of an interface and this proposal gives solution to that
> > problem.
> >
> > Florin,
> > I think the overall concept is good, I want to see something like this in
> > the future, but I think this might be the wrong approach. I don't think
> we
> > should be hinting primitives. if we're going to have a return type hint
> on
> > a method, I would have it match the functionality of the input type hints
> > for functions we already have, where you can hint at an instance of an
> > object type, such as Iterator or StdClass, or an array, but not hint
> > primitives such as int and string, like I currently see in the draft.
> > Also, you should be aware that your proposed syntax for the return type (
> > <type> ) is interfering with:
> > https://wiki.php.net/rfc/protocol_type_hintingand seems unnecessary to
> > me.
>
> Thanks Maxwell, you summarized very well what I was thinking about it.
> So +1 from me for the general feature at a first glance, but it should
> then be very close to what is possible with input type hinting.
>
> It makes it possible to write interfaces that acts like specifications
> and to easier the writing of:
>
> class Foo {
>     public function bar($input) {
>         $return = Baz::foo($input);
>         if (!$return instanceof ReturnType)
>             trigger_error("Cannot divide by zero", E_USER_ERROR); //
> or throwing some RuntimeException
>
>         return $return;
>     }
> }
>
> to:
>
> class Foo {
>     public function <ReturnType> bar($input) {
>         return Baz::foo($input);
>     }
> }
>

+1 for the global idea as this would help so much OO programs and framework
based programs.

But what Sherif said proves as well the limits of the idea. PHP is not
strongly typed. So each check, should it be type hinting or return type
hinting, has to be done at runtime , which is bad for performances.

Not talking about the type juggling which could lead the programmer as
shooting himself.

Julien.Pauli

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