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Date: Mon, 16 Nov 2015 20:54:07 -0500
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To: Chris Riley <t.carnage@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Immutable modifier
From: ircmaxell@gmail.com (Anthony Ferrara)

Chris,

On Mon, Nov 16, 2015 at 4:15 AM, Chris Riley <t.carnage@gmail.com> wrote:
> Hi,
>
> There has been a lot of interest recently (eg psr-7) in immutable data. I'm
> considering putting an RFC together to add language support for immutables:
>
> immutable class Foo {
> public $bar;
> public function __construct($bar) {
> $this->bar = $bar;
> }
> }
>
> Immutable on a class declaration makes all (maybe only public?) properties
> of the class immutable after construct; assigning to a property would
> result in a Fatal error.
>
> class Foo {
> public $bar;
> immutable public $baz;
> }
>
> Immutable on a property makes the property immutable once it takes on a
> none null value. Attempts to modify the property after this results in a
> fatal error.

Beyond syntax/whatever, I would suggest finding a method to do it
internally. That's going to be the biggest problem in my experience
(finding some way of doing it efficiently)...

Anthony