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Date: Tue, 26 Feb 2013 09:41:59 +0300
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To: Nikita Popov <nikita.ppv@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Allow (...)->foo() expressions not only for `new`
From: dmitry@zend.com (Dmitry Stogov)

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Hi Nikita,

I like the idea.
But note, that it may cause some unexpected behaviour and bugs.
I didn't test the patch I just guess it on my previous experience
introducing similar features.

- usage expression in write context (e.g. passing constant by reference)

function foo(&$foo) {}
foo("abc"[0]);

- destruction of temporary result

($a . $b)[4]; // if ($a.$b) is destroyed?

- in some cases destruction of temporary result may cause destruction of
final result

((object)(array("a"=>"b")))->a = "c"; // temporary object may be destroyed
before assignment

All these edge cases must be carefully analyzed.
I like the current patch, and in case the edge cases won't require many
hacks, I'm all for it.

Thanks. Dmitry.


On Mon, Feb 25, 2013 at 8:14 PM, Nikita Popov <nikita.ppv@gmail.com> wrote:

> Hi internals!
>
> PHP 5.4 added support for expressions of the kind (new Foo)->bar(), (new
> Foo)->bar and (new Foo)['bar'].
>
> I'd like to extend this support to any expression instead of just new.
>
> Why should be do this? Because it's just an arbitrary restriction. Removing
> it would for example allow clone calls in the parens, so you could do
> something like (clone $date)->modify('...'). Which - you may have already
> noticed this - is more or less a replacement for the DateTimeImmutable
> class that was added for 5.5 (with the nice benefit of being fully
> compatible and not being an object oriented abomination :) That's just one
> example, but I think there are a lot more (especially if you also consider
> that it allows array dereferencing too). One further use that is of
> interest to me personally is for https://github.com/nikic/scalar_objects,
> so I can do calls like ("foo")->bar().
>
> A nice side benefit from this is that it removes a shift/reduce conflict
> from the parser.
>
> The patch for the change can be found here:
> https://github.com/php/php-src/pull/291/files. It's a very simple patch,
> it
> basically just changes one parser rule and adjusts the allowed opp types
> for some opcodes. The rest is just the vm regeneration for the new op
> types.
>
> I hope that this change is trivial enough to not require dragging it
> through the whole RFC process. If there are no objections I'd commit it
> sometime soon.
>
> Thoughts?
> Nikita
>

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