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Date: Sat, 7 Feb 2015 22:11:45 +0000
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To: =?utf-8?Q?Pavel_Kou=C5=99il?= <pajousek@gmail.com>
Subject: Re: [PHP-DEV] [VOTE] Scalar Type Hints
From: ajf@ajf.me (Andrea Faulds)

Hi,

> On 7 Feb 2015, at 22:03, Pavel Kou=C5=99il <pajousek@gmail.com> wrote:
>=20
> On Sat, Feb 7, 2015 at 9:57 PM, Andrea Faulds <ajf@ajf.me> wrote:
>> Hi,
>>=20
>>> On 7 Feb 2015, at 20:47, Andrea Faulds <ajf@ajf.me> wrote:
>>>=20
>>>> On 7 Feb 2015, at 10:57, Pavel Kou=C5=99il <pajousek@gmail.com> =
wrote:
>>>>=20
>>>> I just realized it now (I brought it up in a different manner when
>>>> there was discussion about the RFC), but I didn't notice there was =
a
>>>> totally false statement about it in the RFC itself. You probably
>>>> should fix it. I'm speaking about the "Strict type checking, which =
is
>>>> used by many popular programming languages, particularly ones which
>>>> are statically-typed, such as Java, C#, Haskell, or Facebook's =
Hack.
>>>> It is also used for non-scalar parameter type hints in PHP. With =
this
>>>> approach, an argument is only accepted if its type is exactly the =
same
>>>> as the parameter." paragraph.
>>>>=20
>>>> This is NOT true (at least for C# and Java), as you can read here =
in
>>>> the documentations of respecitve languages so you should not =
compare
>>>> the strict version of the typing implemented in PHP with other
>>>> strongly typed languages, because the PHP's "strict" is stricter =
than
>>>> strongly static typed languages. I really hope noone voted with the
>>>> thought that the strict typing acts as it does in Java and C#.
>>>>=20
>>>> https://msdn.microsoft.com/en-us/library/y5b434w4.aspx
>>>> =
http://docs.oracle.com/javase/specs/jls/se7/html/jls-5.html#jls-5.1.2
>>>=20
>>> I don=E2=80=99t think it=E2=80=99s unfair. There=E2=80=99s a limited =
set of permitted conversions in some strictly-typed languages, but =
it=E2=80=99s still strictly-typed.
>>=20
>> To add to the previous email:
>>=20
>> * Most of these conversions are between different sizes of the same =
type (float/double, char/short/int/long, etc.), but this is irrelevant =
to PHP which has only one size for each type
>> * The other ones are between types (int to float)
>> * Always allowing implicit conversions from float to int is very =
likely to cause data loss, so it=E2=80=99s not unreasonable for PHP to =
prevent this specific case
>> * Always allowing implicit conversions from int to float is sometimes =
going to cause data loss, so it may also be reasonable for PHP to =
prevent this specific case
>> * Requiring an exact type match has the least mental overhead, and =
allows types to be checked at compile-time
>>=20
>=20
> Yeah, but you say in the RFC that "With this approach, an argument is
> only accepted if its type is exactly the same as the parameter." when
> speaking about C# and Java - which is NOT true.

C# and Java aren=E2=80=99t really considered weakly-typed. Technically =
they=E2=80=99re not =E2=80=9Cfully strict=E2=80=9D I guess, but if you =
were to give example of strictly-typed languages, you=E2=80=99d probably =
include C# and Java in that list - so I did.

> You should have
> written that the way of strict typing in PHP is even more strict than
> Java's and C# one - because the way it's written now is unfortunately
> misinforming the readers of the RFC.

It might be somewhat misleading. Really, what=E2=80=99s =E2=80=9Cweak=E2=80=
=9D and what=E2=80=99s =E2=80=9Cstrict=E2=80=9D is rather subjective: C =
is sometimes considered weak, sometimes strict. I=E2=80=99d say it=E2=80=99=
s more =E2=80=9Cweak=E2=80=9D because all sorts of definitely wrong =
conversions are allowed implicitly and merely generate warnings. C# and =
Java are more careful here, so I=E2=80=99d say they=E2=80=99re =
=E2=80=9Cstrict=E2=80=9D even though I suppose they do have a degree of =
weak typing.

> Also, there's no need to mention
> float -> int, because that one is definitely wrong. But for the int
> (and long, etc) -> float (and double) - how do the languages you
> mentioned in the RFC handle that conversion?

=46rom Microsoft=E2=80=99s documentation that you linked, it sounds like =
they just always convert and never error, so you=E2=80=99d get data loss =
in some cases (just like you do in PHP with an explicit cast).

> I'm wishing more and more that the RFC doesn't pass (even though I'd
> LOVE to have typehints in PHP as a userland developer) and someone
> else will make a better version of typehints RFC for  PHP 7, because
> this one feels really like you took an ok-ish RFC (one that would be
> good for PHP) and slapped a strict typing on it without enough
> research about strong typing in other languages.

I am familiar with other languages, I just disagree with their approach.

> And as I said myself
> multiple times in the past, the declare syntax IS just ugly (and
> changing how code works by writing one line is an ugly principle as
> well, IMHO). :(

I prefer this approach to the inconsistency the other approaches =
suggested thus far lead to.
--
Andrea Faulds
http://ajf.me/