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Date: Wed, 15 Mar 2017 11:36:24 +0100
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To: Sara Golemon <pollita@php.net>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Unexpected results from constant folding
From: nikita.ppv@gmail.com (Nikita Popov)

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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

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