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Date: Wed, 25 May 2016 16:47:19 +0200
Message-ID: <CANUQDCj0O6aVwTqo+CcAbX8AWvwPQHfhRtsYRUrMS_aFjHM5RQ@mail.gmail.com>
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: Joe Watkins <pthreads@pthreads.org>, Dmitry Stogov <dmitry@zend.com>, 
	PHP internals <internals@lists.php.net>, Phil Sturgeon <pjsturgeon@gmail.com>, 
	Bob Weinand <bwoebi@php.net>
Content-Type: multipart/alternative; boundary=001a114b9fd42a0c460533abc091
Subject: Re: [PHP-DEV] [RFC][Vote] Typed Properties
From: me@kelunik.com (Niklas Keller)

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>
> On Wed, May 25, 2016 at 10:30 AM, Joe Watkins <pthreads@pthreads.org>
> wrote:
>
> > Morning Dmitry,
> >
> >    > I made this check(s) to be invariant. You may like to do this
> > differently...
> >
> >    I think this is what everyone expects, isn't it ?
> >
> >    I did omit to mention that part ...
> >
> >    > RFC doesn't define how uninitialized nullable typed properties
> should
> > behave.
> >
> >   It does:
> >
> >    > *Nullable typed properties will not raise an exception when accessed
> > before initialization.*
> >
>
> I don't agree with this choice, for three reasons:
>
> a) This unnecessarily restricts what can be expressed in the type system.
> With these semantics it will no longer be possible to express that a
> property should be nullable, but have no default value. This situation is
> not uncommon in practice, in particular anytime you have a nullable
> constructor argument, you will want the corresponding property to be
> nullable without a default, to ensure that it is explicitly initialized.
>

I disagree here. Properties are always null by default. The current patch
disallows
access to uninitialized variables only if they're not nullable, since null
isn't a valid value then.

I don't think having to explicitly set them to null is the think we want.
And it's not what I'd expect given the current system.


> b) This directly contradicts the meaning of ?Type for parameters. For
> parameters ?Type means that it's a nullable parameter **without a default
> value**. That's the very thing that distinguishes it from the Type $prop =
> null syntax. And now ?Type for properties should mean the exact opposite?
>

These have always been different. `private $foo` has always been `null` by
default,
while `function($foo)` doesn't have a default value.


> c) If you view this in a larger scope of union types, this *special case*
> becomes even more weird. Why does the particular union Type|null get
> special treatment, while all other unions don't? Or is it actually not
> specific to "null", but to single value types? E.g. if we also allowed
> Type|false, would that also receive an implicit false default value? What
> about the type null|false? Does that get an implicit default, and if so,
> which? I realize this is not quite in scope for type properties, but the
> further evolution of the type system should be kept in mind.
>

I think this is something unions should address. I'm personally still not a
fan of union types,
as they try to solve the wrong problem, mostly things like array not being
instance of Traversable.

Regards, Niklas


> Please keep things consistent: If there is not default, there is no
> default.
>
> Nikita
>

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