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To: internals@lists.php.net, Stanislav Malyshev <smalyshev@gmail.com>
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Date: Thu, 26 May 2016 18:20:20 +0100
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Subject: Re: [PHP-DEV] [RFC][Vote] Typed Properties
From: rowan.collins@gmail.com (Rowan Collins)

On 26/05/2016 17:57, Fleshgrinder wrote:
> On 5/26/2016 6:50 PM, Rowan Collins wrote:
>> As I'm sure has already been pointed out (I haven't followed the whole
>> thread) this defeats a large advantage of typed properties - I now can't
>> read from the property without checking if it's null, so I can't do this:
>>
>> class O {
>>    public \DateTimeImmutable $d;
>> }
>> echo (new O)->d->format('Y-m-d H:i:s');
>>
>> There's no ? on the type def, so I ought to be able to trust the type. A
>> TypeError makes more sense here, because it is a programming error for
>> it to be in this state.
>>
>
> That is exactly what Stanislav raised too. I really have no idea how we
> should prevent this from happening and honestly think we shouldn't. Your
> construct will result in a fatal error (also known as
> NullPointerException to some, *evil-laughter*) anyways preceded by an
> E_NOTICE that tells you that your property is not defined.
>
> I am of course open for ideas but emitting another kind of fatal error
> does not really make things better imho.

I think the difference is the emphasis of whose responsibility it is to 
fix it: a TypeError confirms that the error is in the O class for 
exposing an incorrectly typed property; a NullPointerException, as you 
put it, makes it my fault for trusting the class.

Or to put it a different way, is the error in the first arrow (accessing 
"->d") or the second one (de-referencing "d->").


At the end of the day, all the type notations being added to PHP are 
just assertions anyway. So the same could be said of this:

function foo(\DateTime $d) {
    echo $d->format('Y-m-d H:i:s');
}
foo(null);

If this didn't throw an error at "foo(null)", it would throw an error at 
"$d->format".


Regards,
-- 
Rowan Collins
[IMSoP]