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Date: Tue, 17 Feb 2015 01:15:33 +0400
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To: Nikita Popov <nikita.ppv@gmail.com>
Cc: Benjamin Eberlei <kontakt@beberlei.de>, PHP Internals <internals@lists.php.net>, 
	Guilherme Blanco <guilhermeblanco@gmail.com>, Pierrick CHARRON <pierrick@webstart.fr>, 
	Alexander Lisachenko <lisachenko.it@gmail.com>, Pierre Joye <pierre.php@gmail.com>, 
	Zeev Suraski <zeev@zend.com>, Andi Gutmans <andi@zend.com>, Joe Watkins <pthreads@pthreads.org>, 
	Yasuo Ohgaki <yohgaki@ohgaki.net>, Sebastian Bergmann <sebastian@php.net>, 
	Stanislav Malyshev <smalyshev@gmail.com>, Rasmus Lerdorf <rasmus@lerdorf.com>
Content-Type: multipart/alternative; boundary=20cf3071c7c02e289a050f3b16d0
Subject: Re: [PHP-DEV] Annotations in PHP7
From: dmitry@zend.com (Dmitry Stogov)

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Hi Nikita,

On Tue, Feb 17, 2015 at 12:07 AM, Nikita Popov <nikita.ppv@gmail.com> wrote:

> On Mon, Feb 16, 2015 at 10:02 PM, Dmitry Stogov <dmitry@zend.com> wrote:
>
>>
>>
>> On Mon, Feb 16, 2015 at 11:05 PM, Benjamin Eberlei <kontakt@beberlei.de>
>> wrote:
>>
>>>
>>>
>>> On Mon, Feb 16, 2015 at 12:07 PM, Dmitry Stogov <dmitry@zend.com> wrote:
>>>
>>>> hi,
>>>>
>>>> During discussion of different ways of implementing "Design by
>>>> Contract" we
>>>> got an idea of using annotations.
>>>>
>>>> BTW: annotations are useful by their own and may be used for different
>>>> purposes. Support for annotations was proposed long time ago:
>>>>
>>>> https://wiki.php.net/rfc/annotations
>>>> https://wiki.php.net/rfc/annotations-in-docblock
>>>> https://wiki.php.net/rfc/reflection_doccomment_annotations
>>>>
>>>> HHVM already implemented similar concept
>>>>
>>>> http://docs.hhvm.com/manual/en/hack.attributes.php
>>>>
>>>> I made a quick and dirty PoC that shows how we may implement
>>>> annotations in
>>>> PHP7 and how powerful they may be :
>>>> https://gist.github.com/dstogov/dbf2a8f46e43719bd2c2
>>>
>>>
>>> How about not exposing the AST, and then the userland can pass context
>>> to a method $reflection->getAnnotation($name, $context);
>>>
>>> https://gist.github.com/beberlei/0dc36d4412b8e3454912
>>>
>>> That way AST is not exposed to userland.
>>>
>>
>> Your example handles just particular use-case.
>> I would like to provide a general solution.
>>
>> Thanks. Dmitry.
>>
>
> Could you provide some more info on how you would imagine this to be used
> for the DbC use case? As far as I see, this would require injecting code
> into the method body based on the annotations. Does that mean that
> annotations handlers will get the chance to modify the AST of the method
> itself during compilation? Or how is this supposed to be realized?
>

In general, it must be possible to plug into compilation process using
zend_ast_process() callback and modify function AST, inserting constraints
validation in proper places.
But for now, I'm thinking only about metadata syntax and representation. I
just showed, how it can be used to represent DbC constraints.
I don't think we need user-level interface to modify AST.

Thanks. Dmitry.


>
> Nikita
>

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