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To: Stas Malyshev <smalyshev@sugarcrm.com>
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        Larry Garfield
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Thread-Topic: [PHP-DEV] [RFC] Return Type Declarations pre-vote follow-up
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Date: Mon, 12 May 2014 18:12:43 +0000
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Subject: Re: [PHP-DEV] [RFC] Return Type Declarations pre-vote follow-up
From: jwatzman@fb.com (Josh Watzman)

On May 12, 2014, at 12:34 AM, Stas Malyshev <smalyshev@sugarcrm.com> wrote:

> Hi!
>=20
>> Docblocks is not the solution. If you want to take profit of static
>> analysis without the penalty of runtime type checking, Hack has shown th=
e
>> way with its "soft type hints".
>=20
> What prevents you from doing static analysis using types specified in
> docblocks?

For context/background. Hack has deliberately resisted doing this since we =
consider the types to be an integral part of the language. Runtime enforcem=
ent is very important for this. You need something to make sure the static =
analysis of the type system is not just self-consistent but consistent with=
 reality. Until pretty close to the open source release of Hack, HHVM didn'=
t actually enforce return types. Facebook had to do quite a bit of cleanup =
here, since the return type enforcement uncovered a bunch of places where t=
he types were self-consistent but not grounded in reality.

So in our opinion putting things in docblocks just compounds this problem a=
nd can be pretty dangerous if nothing is enforcing them at runtime.

So this may or may not be a good idea for your use case (I've honestly kind=
 of lost where this branch of the email thread was going), but that's why w=
e haven't done it for Hack.

Josh Watzman