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References: <7.0.1.0.2.20100522175819.0a601c68@zend.com> <AANLkTikHOL_Tp1jhhOVTD3cFbnw0eA1zAVWKJx0BU1W4@mail.gmail.com> 
	<7.0.1.0.2.20100523073125.0a601600@zend.com> <201005230052.05661.larry@garfieldtech.com>
Date: Sun, 23 May 2010 09:52:31 +0200
Message-ID: <AANLkTilDx9iCVfRBrx3O5zexnIqtCYpWbXeihk8IebUz@mail.gmail.com>
To: Larry Garfield <larry@garfieldtech.com>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] Type hinting
From: peter.e.lind@gmail.com (Peter Lind)

On 23 May 2010 07:52, Larry Garfield <larry@garfieldtech.com> wrote:
> On Saturday 22 May 2010 11:43:50 pm Zeev Suraski wrote:
>> At 01:01 23/05/2010, Hannes Magnusson wrote:
>> >On Sat, May 22, 2010 at 22:39, Lukas Kahwe Smith <mls@pooteeweet.org>
> wrote:
>> > > On 22.05.2010, at 18:30, Josh Davis wrote:
>> > >> As you wrote, you worked on PHP's _type system_ which is dynamic,
>> > >> really cool, juggles strings with ints and what not. However, the
>> > >> topic here is the _type hinting system_. As far as I know, there's =
no
>> > >> "weak" type hinting; if a method signature hints for an array and i=
s
>> > >> given an integer, it throws a catchable fatal error. Therefore, as =
a
>> > >> user, what I am familiar to is a strict _type hinting system_.
>> > >> Anything else would feel inconsistent to me.
>> >
>> >I agree. function foo(array $x) {} foo(123); doesn't cast int(123) to
>> >array(123) so introducing different meaning for scalar types feels
>> >very very wrong.
>>
>> You're ignoring one simple fact - in PHP, scalar types are
>> interchangeable. =C2=A0Unlike array->scalar which has always been a corn=
er
>> case and a sketchy one (and I said numerous times that had I rewrote
>> the language now, array->scalar conversion would have probably
>> resulted in an error) - string->number, number->string,
>> string->boolean conversions are a cornerstone of the language. =C2=A0If
>> you don't like the fact that PHP's scalar types are interchangeable -
>> you're in the wrong language!
>>
>> In terms of consistency, the difference between array type hinting
>> and scalar type hinting you allude to is negligible in comparison to
>> the inconsistency with, well, just about every other part of the
>> language - operators, control structures and built-in functions
>> (expecting sqrt("64") to fail, since sqrt() expects a
>> number? =C2=A0expecting if (7) to fail, since it expects a
>> boolean?). =C2=A0Auto-converting type hinting extends the same semantics
>> available to internal functions (through zend_parse_parameters()) to
>> userland functions. =C2=A0That consistency is by far the most important =
IMHO.
>>
>> Zeev
>
> I have to largely agree with Zeev here. =C2=A0I'm not an internals develo=
per but I
> do write a lot of widely used framework-ish open source PHP.
>
> The current OO type specifying system I have always mentally viewed, and =
most
> people I know seem to view it, as a check not for "is this an X", but "ca=
n I
> treat this as X without things exploding"? =C2=A0In the context of an obj=
ect,
> "exploding" would mean a "method not found" fatal. =C2=A0In the context o=
f an
> array, it would be the dreaded "parameter 1 to foreach() is not an array"=
.
> The idea is two fold: One, better documentation (especially for code
> assistance IDEs), and two, if it's going to explode it should explode in =
a way
> that's useful in terms of where it exploded. =C2=A0(Vis, the error messag=
e is on a
> useful line and tells me what the actual problem was.)
>
> For scalar types, exploding would mean "loss of precision". =C2=A0There i=
s no loss
> of precision in converting "5" to int(5), so that doesn't explode, nor sh=
ould
> it. =C2=A0There is similarly no loss of precision converting from int(5) =
to
> float(5), so that also shouldn't explode. =C2=A0"123abc" does have a loss=
 of
> precision (data would get lost in the conversion) so that should fail bot=
h int
> and float checks.
>
> If anything, I'd be even more forgiving than the table in Zeev and Lukas'=
 RFP.
> float(12) converting to an int doesn't have any precision loss so I don't=
 think
> that should fail.
>
> The RFP includes a variety of good reasons why a more naive strict check =
is
> inconsistent to the point of making it a bug rather than a feature. =C2=
=A0One in
> particular I want to call out: Everything that comes back from a database=
 does
> so as a string. =C2=A0To wit:
>
> table users(user_id, name, pass, blah);
>
> $user_id =3D $pdo->query("SELECT user_id FROM users WHERE name=3D'bob' AN=
D
> pass=3D'foo'")->fetchColumn();
>
>
> doStuff($user_id);
>
> function doStuff(int $user_id) {
> =C2=A0// Whatever.
> }
>
>
> The above code will fail with the current implementation, even though we =
know
> for a fact that user_id is integer data because that column is an int in =
the
> database itself. =C2=A0Requiring an extra blind (int) stuffed in there is=
 pointless,
> and if anything just trains people to blindly cast data without thinking =
about
> what it really is. =C2=A0I can see that introducing more bugs than it avo=
ids.
>
> --Larry Garfield
>

+1

Regards
Peter

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