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Date: Tue, 26 Feb 2013 17:49:08 +0100
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To: Dmitry Stogov <dmitry@zend.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Allow (...)->foo() expressions not only for `new`
From: nikita.ppv@gmail.com (Nikita Popov)

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On Tue, Feb 26, 2013 at 7:41 AM, Dmitry Stogov <dmitry@zend.com> wrote:

> 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.
>

I just played a bit with it and came up with the following (additional)
patch to support use in write context:
https://github.com/nikic/php-src/commit/31705dd8c53efe3bb52d6aae483a324e5a511ae9It
throws an error if the write is done on a TMP or CONST, but things
like
(new foo)->bar = 'x' will work. Though I'm not quite sure whether this is
really necessary, at least I don't see much use for it.

Reading your mail again, I missed the second point (about destruction of
temporary). But I wonder how it could cause any issue. I mean, FREE op is
only inserted when expression is used as statement, which is not the case
here. Or am I missing something?

Nikita

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