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Date: Sat, 11 Jul 2020 08:29:33 -0600
Message-ID: <CAK70goPOPjDXHKvaDBkg++2jve2cMWXgPiZM86JnL_3Yc3rnTg@mail.gmail.com>
To: =?UTF-8?Q?Olle_H=C3=A4rstedt?= <olleharstedt@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Possible RFC: UniqueInterface that throws exception at
 refcount > 1
From: cja987@gmail.com (Chuck Adams)

On Sat, Jul 11, 2020 at 8:06 AM Olle H=C3=A4rstedt <olleharstedt@gmail.com>=
 wrote:
>
> Dear internals,
>
> I'd like to discuss the concept of ownership in PHP, from the point of
> view of a new interface UniqueInterface (or SplUniqueInterface or
> something), which will throw a UniqueException if refcount > 1.
>
> Use-case: Mutable objects that cannot be shared (without (deep) cloning).

I don't think you want to do this on refcount, since that would
prevent even passing it to another function or using it in any number
of expressions.  What would make more sense to me would be hooking
into copy-on-write, which would also be a slightly less hot code path
than reference counting (but still a pretty critical one).

It almost sounds like a uniqueness type, something well beyond the
capabilities of PHP's type system (and most others).

--c