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Date: Thu, 15 Jan 2015 15:36:50 +0000
Cc: Jordi Boggiano <j.boggiano@seld.be>,
 PHP internals <internals@lists.php.net>
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References: <8DCD1B72-C81D-499E-B455-E4A042CD76E6@ajf.me> <54B7D8AE.5090209@seld.be> <CAB6YZuxA5F7DT+4F5FznrTuw_jR52-0KD2MPvMqhUhs-h9B-2g@mail.gmail.com>
To: =?utf-8?Q?Pavel_Kou=C5=99il?= <pajousek@gmail.com>
Subject: Re: [PHP-DEV] [RFC] Scalar Type Hints v0.2
From: ajf@ajf.me (Andrea Faulds)

Hi Pavel,

> On 15 Jan 2015, at 15:25, Pavel Kou=C5=99il <pajousek@gmail.com> =
wrote:
>=20
> On Thu, Jan 15, 2015 at 4:11 PM, Jordi Boggiano <j.boggiano@seld.be> =
wrote:
>>=20
>> Reading the thread at this point shows so much confusion, it seems =
half the
>> people reading the spec misunderstood that the declare() line affects
>> function calls only and not the API/implementation level.
>=20
> Yeah, while the confusion is definitely still there, I would
> personally argue that definitely some people who oppose the declare()
> get that it's only for calls in the file - and still don't find it
> clever.
>=20
> The potential issues with this are pretty real, to be honest. Simple
> things like moving a method from one class to another (let's say to
> parent or descendant) and getting to another typing context may cause
> unpredictable behavior if the user forgets to have declare() in both
> files.

This is true, you would sometimes have problems if you=E2=80=99re mixing =
the strict and weak type checking modes in your codebase.

The intention is that you=E2=80=99d use one or the other exclusively, =
perhaps with some minor exceptions as and where necessary. The fact =
it=E2=80=99s weak by default means you could add scalar type hints =
gradually without breaking things, because the weak mode is quite =
permissive. Then, if you wanted to, you could gradually migrate each =
file in your codebase over to strict mode.

Essentially, you get =E2=80=9Cgradual typing=E2=80=9D like Hack, but =
without Hack=E2=80=99s approach which I don=E2=80=99t particularly like. =
Hack=E2=80=99s approach is to simply not enforce type hints if they=E2=80=99=
re a problem. On the other hand, this RFC would alway enforces them, but =
the weak mode is less strict.

So, I anticipate that while it would cause problems during a transition, =
I think codebases would end up using one mode or the other exclusively =
and wouldn=E2=80=99t have problems once they had done so.

Thanks.
--
Andrea Faulds
http://ajf.me/