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To: Lorenzo Fontana <fontanalorenz@gmail.com>,
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Cc: internals@lists.php.net, Chris Riley <t.carnage@gmail.com>
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Date: Mon, 16 Nov 2015 11:00:49 +0100
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Subject: Re: [PHP-DEV] Immutable modifier
From: mathieu@rochette.cc (Mathieu Rochette)

hi,

On 16/11/2015 10:33, Lorenzo Fontana wrote:
> I really like the concept of immutability, but I think that it should be
> applicable at  instance level rather than declaration.
I'm not sure about that, most PHP code assume mutable objects, I doubt 
much existing classes would be usable as immutable
>
> I would also prefer another keyword than immutable.
>
> Final does not make the properties immutable, it makes the class not
> extensible.
> On Nov 16, 2015 10:24, "Daniel Persson" <mailto.woden@gmail.com> wrote:
>
>> Any differance from the final keyword?
>>
>> http://php.net/manual/en/language.oop5.final.php
>>
>> On Mon, Nov 16, 2015 at 10:15 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
I don't think it's enough to make only public properties immutable. this 
would lead to a lot of mutable "immutable" classes, eg:

immutable class my_class {
   private $my_prop;
   __construct($my_prop) {
     $this->my_prop = $my_prop;
   }
   public function getMyProp() {
     return $this->my_prop;
   }
   public function setMyProp($my_prop) {
     return $this->my_prop = $my_prop;
   }
}

how is this class immutable ?
also, what about __isset/__set ? Would it be allowed to assign non 
immutable types to properties of an immutable class ?
>>> 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.
>>>
>>> Any thoughts?
>>> ~C
>>>