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Date: Thu, 30 May 2024 11:35:42 +0300
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Subject: Re: [PHP-DEV] [RFC] Asymmetric Visibility, v2
To: php internals <internals@lists.php.net>
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From: drealecs@gmail.com (=?UTF-8?Q?Alexandru_P=C4=83tr=C4=83nescu?=)

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On Wed, May 29, 2024 at 10:18=E2=80=AFPM Larry Garfield <larry@garfieldtech=
.com>
wrote:

> As promised, Ilija and I offer this revised version of asymmetric
> visibility.
>
> https://wiki.php.net/rfc/asymmetric-visibility-v2
>
>
Hey Larry, Ilija,

I have one concern so far, and it's related to the inheritance section.

If in a class I define the property as private,
I know that there is no way for external scope or extending classes scope
to read or write to the property.
(of course, ignoring reading/writing using reflection or re-binded closures=
)

If an extending class defines the property with a wider visibility,
protected or public, it will shadow the initial one and not change its
visibility.

Now, if I define the property as public private(set) (or protected
private(set)) with similar intentions,
to make sure that there is no way for external scope or extending classes
scope to write to the property,
while allowing reading from external scope (or extending classes scope).

But the problem is that an extending class can define the property as
public protected(set) (or protected protected(set)),
and that will easily allow the property that I wanted to make sure it is
private for writing to be changed by an extending class to be protected.


The main suggestion I can think of, is to now allow widening the write
visibility when it is private.

I mean, in general, to make sure it is not possible for other extending
classes to access private parent class properties/methods we can use two
mechanisms:
- disallowing to change the visibility and making it an error
- shadowing the parent property/method
While shadowing works for symmetric visibility, it doesn't really work for
asymmetric visibility, so disallowing seems to be a good option here.

Also, maybe marking the properties as final could play a role here,
not allowing private visibility for write on properties to be widened or
completely not allowing it to change/redefined.


Regards,
Alex

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><div class=3D"gmail_quote"><div=
 dir=3D"ltr" class=3D"gmail_attr">On Wed, May 29, 2024 at 10:18=E2=80=AFPM =
Larry Garfield &lt;<a href=3D"mailto:larry@garfieldtech.com">larry@garfield=
tech.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D=
"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-le=
ft:1ex">As promised, Ilija and I offer this revised version of asymmetric v=
isibility.=C2=A0 <br>
<br>
<a href=3D"https://wiki.php.net/rfc/asymmetric-visibility-v2" rel=3D"norefe=
rrer" target=3D"_blank">https://wiki.php.net/rfc/asymmetric-visibility-v2</=
a><br>
<br></blockquote><div><br></div><div>Hey Larry, Ilija,</div><div><br></div>=
I have one concern so far, and it&#39;s related to the inheritance section.=
</div><div class=3D"gmail_quote"><br></div><div class=3D"gmail_quote">If in=
 a class I define the property as private,</div><div class=3D"gmail_quote">=
I know that there is no way for external scope or extending classes scope t=
o read or write to the property.</div><div class=3D"gmail_quote">(of course=
, ignoring reading/writing using reflection or re-binded closures)</div><di=
v class=3D"gmail_quote"><br></div><div class=3D"gmail_quote">If an extendin=
g class defines the property with a wider visibility, protected or public, =
it will shadow the initial one and not change its visibility.</div><div cla=
ss=3D"gmail_quote"><br></div><div class=3D"gmail_quote">Now, if I define th=
e property as public private(set) (or protected private(set)) with similar =
intentions,</div><div class=3D"gmail_quote">to make sure that there is no w=
ay for external scope or extending classes scope to write to the property,<=
/div><div class=3D"gmail_quote">while allowing reading from external scope =
(or extending classes scope).</div><div class=3D"gmail_quote"><br></div><di=
v class=3D"gmail_quote">But the problem is that an extending class can defi=
ne the property as public protected(set) (or protected protected(set)),</di=
v><div class=3D"gmail_quote">and that will easily allow the property that I=
 wanted to make sure it is private for writing to be changed by an extendin=
g class to be protected.</div><div class=3D"gmail_quote"><br></div><div cla=
ss=3D"gmail_quote"><br></div><div class=3D"gmail_quote">The main suggestion=
 I can think of, is to now allow widening the write visibility when it is p=
rivate.</div><div class=3D"gmail_quote"><br></div><div class=3D"gmail_quote=
">I mean, in general, to make sure it is not possible for other extending c=
lasses to access private parent class properties/methods we can use two mec=
hanisms:</div><div class=3D"gmail_quote">- disallowing=C2=A0to change the v=
isibility and making it an error</div><div class=3D"gmail_quote">- shadowin=
g the parent property/method</div><div class=3D"gmail_quote">While shadowin=
g works for symmetric=C2=A0visibility, it doesn&#39;t really work for asymm=
etric=C2=A0visibility, so disallowing=C2=A0seems to be a good option here.<=
br></div><div class=3D"gmail_quote"><br></div><div class=3D"gmail_quote">Al=
so, maybe marking the properties as final could play a role here,</div><div=
 class=3D"gmail_quote">not allowing private visibility for write on propert=
ies to be widened or completely not allowing it to change/redefined.</div><=
div class=3D"gmail_quote"><br></div><div class=3D"gmail_quote"><br></div><d=
iv class=3D"gmail_quote">Regards,</div><div class=3D"gmail_quote">Alex</div=
><div class=3D"gmail_quote"><br></div></div>

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