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Date: Tue, 22 Mar 2016 13:15:30 +0000
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Subject: Re: [PHP-DEV] [RFC Discussion] Typed Properties
From: rowan.collins@gmail.com (Rowan Collins)

Nikita Popov wrote on 21/03/2016 17:05:
> While it is no secret that we don't particularly like references, this 
> is not the reason why they are forbidden. There is no conspiracy to 
> punish users of references by denying them use of new typing features. 
> No, the reasons here are technical. Let me illustrate some of the 
> issues involved in more detail.


Thanks for the detailed explanation of the problems, which are indeed 
deeper than I'd appreciated. To be clear, I never thought it was the 
intention to dissuade users from using references, but a couple of 
people have implied that they consider it no bad thing.


For me, the restriction on setting references makes this whole feature a 
no-go for the language as it stands. I don't think it is at all 
reasonable for the following code to produce a TypeError:

class Sorter {
     private array $data;
     public function __construct(array $data) {
         $this->data = $data;
         sort($this->data);
     }
}
new Sorter([1,3,6,5,2,4]);


It may be that we've reached the limit of how much typing we can add to 
the language incrementally, and need actual typed variables, so that 
references could be made only between variables with the same type hint, 
e.g.

class A { public int $foo=42; }
$a = new A;
int $ref =& $a->foo;

The sort() example would work in this scenario because the expected 
parameter type is array, so the reference being created is of the 
matching type.

Obviously, this would be a huge change to the language, and no doubt 
have all sorts of impacts and problems of its own, but I don't think it 
makes sense to say "you can typehint your property names, but you lose 
some existing functionality if you do so, for technical reasons".

Regards,
-- 
Rowan Collins
[IMSoP]