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Date: Wed, 15 Mar 2017 09:25:09 -0300
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To: Nikita Popov <nikita.ppv@gmail.com>
Cc: Sara Golemon <pollita@php.net>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Unexpected results from constant folding
From: david.proweb@gmail.com (David Rodrigues)

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Just to make simpler to visualize this issue: https://3v4l.org/ZhYlm

```php
class Foo {
    const A = 'Foo::A';
    const B = self::A . ' and ' . self::C;
    const C = 'Foo::C';

}

class Bar extends Foo {
    const A = 'Bar::A';
    const C = 'Bar::C';
}

var_dump(Bar::B);
```

You should note that:

PHP 7.0 to 7.1.2 => Foo::A and Bar::C
> It will give a result like a self::A and static::C (currently last one is
impossible);

PHP 5.6 to 5.6.30 => Bar::A and Bar::C
> It will give a result like a static::A and static::C;

hhvm 3.12.14 to 3.18.1 => Foo::A and Foo::B
> It will give a result like should be expected on code (both from self::
that is the Foo class);


2017-03-15 7:36 GMT-03:00 Nikita Popov <nikita.ppv@gmail.com>:

> On Wed, Mar 15, 2017 at 3:43 AM, Sara Golemon <pollita@php.net> wrote:
>
> > This comes in thanks to my old friend Fred Emmott on the HHVM project:
> > https://3v4l.org/vUHq3
> >
> > class Foo {
> >     const A = 1 << 0;
> >     const B = self::A | self::C;
> >     const C = 1 << 1;
> >
> > }
> >
> > class Bar extends Foo {
> >     const A = 1 << 2;
> >     const C = 1 << 3;
> > }
> >
> > var_dump(decbin(Bar::B));
> > // HHVM result: 11
> > // PHP5 result: 1100
> > // PHP7 result: 1001
> >
> > HHVM's result is clearly correct as `self::` refers to the defining
> > class and so should bind to Foo's values for A and C.
> > PHP5's result is at least rationally viable, although it effectively
> > redefines `self::` to the semantics of `static::` just for this case.
> > PHP7's result is... well, I can imagine how it occurs, but it can't be
> > called correct by any measure.
> >
> > Opinions on the right thing to do here?
> > a) Leave it alone because it's been that way since 7.0
> > b) Revert to php5 behavior
> > c) Match HHVM's behavior
> >
> > I vote C because that's the semantic meaning of self:: and we should
> > respect PHP's own language rules.
> > Barring that, I'd be okay with B as it's at least explainable without
> > too much mental gymnastics.
> > I straight up veto A.  That's just cray-cray.
> >
>
> Yes, this should behave as C. See also https://bugs.php.net/bug.php?
> id=69676
> for an existing bug report on the topic.
>
> I think in 7.1 it might be even fairly simple so fix this: IIRC we now
> store the defining CE on inherited constants, so we should know the scope
> to resolve against.
>
> Nikita
>



-- 
David Rodrigues

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