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Date: Wed, 18 Mar 2015 15:28:34 +0000
Message-ID: <CAGAGxbaFJ5anL6vr8RYn7=teFsqMSQJYs=pMXACeiaxzzj4vRw@mail.gmail.com>
To: =?UTF-8?Q?Pavel_Kou=C5=99il?= <pajousek@gmail.com>
Cc: Nikita Nefedov <inefedor@gmail.com>, PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=089e014942e68d3a03051191bc56
Subject: Re: [PHP-DEV] [RFC][Accepted] Scalar Type Declarations V0.5
From: cw@daverandom.com (Chris Wright)

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On 18 March 2015 at 13:12, Pavel Kou=C5=99il <pajousek@gmail.com> wrote:

> On Wed, Mar 18, 2015 at 2:02 PM, Nikita Nefedov <inefedor@gmail.com>
> wrote:
> > On 18 Mar 2015 15:52, "Pavel Kou=C5=99il" <pajousek@gmail.com> wrote:
> >>
> >> Hello,
> >>
> >> I made that conclusion because in the first example, the library kinda
> >> forces strict mode rules on the caller, even if he doesn't want to use
> >> strict mode - this makes the interoperability of the two modes
> >> problematic.
> >
> > This is incorrect, library force itself to use right types, not you. I
> don't
> > see any problems here. The only thing that for sure lacks in PHP and th=
at
> > would make STH better is callable signature types.
> >
>
> Well, it forces you to do that, basically. And also forces you to
> "care" about the mode of library, adding mental overhead. Look more
> closesly at the first example - does the error in that case make sense
> to you (from purely user's point of view)? When you call
> a(function(int $b) {return $b * 2; }) - should you really be required
> to check the context within the a() is declared?
>

You don't need to check the declaration context of a(). Either the library
is definitely passing an integer and your code will work, or it isn't
definitely passing an integer, maybe it's a float, so you shouldn't declare
the parameter type at all - it isn't a typed parameter. This is simply a
matter of RTFM in the library docs (and if there are no docs or the docs
are wrong then you have to go read the library code anyway just as you
would today, so you haven't lost anything).

Type declarations are a way to more completely describe the interface
contract, they are *not* a replacement/shorthand for casts. If the desired
behaviour for your callback should be to accept anything and treat it as an
integer for the computation, then your code should be written to describe
that intent, i.e:

a(function($b) {return ((int)$b) * 2; })

This code both describes the behaviour of a() and the programmer's intended
behaviour for the callback. Using a type declaration as a means to force a
cast hides both of these - a reader would assume the callback is always
called with an integer.


>
> >> Also, the other possible outcome of the scenario (respecting the mode
> >> of the place where the callback is declared), is IMHO problematic as
> >> well, because it does not respect the strict mode of the place where
> >> it is called, making it inconsistent with how the dual mode RFC works
> >> in general.
> >
> > It doesn't matter where the callback or function was declared, it only
> > matters where it was called. It pretty much is consistent.
>
> This was just a comment about how it would be (also) wrong to solve it
> the other way around.
>
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