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Date: Sat, 29 Jun 2024 16:56:11 +0100
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Subject: Re: [PHP-DEV] [RFC] Static class
To: Ayesh Karunaratne <ayesh@php.watch>
Cc: php internals <internals@lists.php.net>
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From: bilge@scriptfusion.com (Bilge)

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Hi Ayesh,

On 24/06/2024 08:53, Ayesh Karunaratne wrote:
>   - Why is it a class-level flag and not an attribute (similar to the `#[Override]` attribute in PHP 8.3) ?
I believe Tim already answered this, and I understood his reasoning to 
be that keywords are used when they modify behaviour in a way that is 
meaningful for the consumer of that class. Or to put it another way, 
attributes are purely informational. For me personally, introducing an 
attribute never crossed my mind, and since we already have the keyword 
in the language performing a similar function in PHP, and other 
languages already, it seems nonsense to contemplate anything else.
>   - Can a subclass extend a static parent class without using the
> `static` keyword in the subclass? This will avoid a lot of BC issues
> if a library decides to declare classes as static.
No, a static parent implies a static child, but implied or not, it must 
still be specified explicitly. I may need to clarify that in the RFC, so 
thanks for the question.
>   - Are there any opt-out mechanisms for subclasses?
Not sure what you mean exactly, but if you mean, can a static subclass 
suddenly become non-static, the answer is no.Again thanks for the 
question, as this is also something I had no previously considered.
>   - Can you mark interfaces, abstract classes, and Enums as static?

It seems others avoided addressing this question, and honestly I was not 
really sure where to go with this one. What would it mean for an enum to 
be static? I thought the whole point was we can type a group of values, 
but static classes have no meaning within the type system, so I cannot 
see the application.

As for abstract classes, the current version of the RFC (1.2) now 
declares static mutually exclusive with abstract, so the answer there is 
also no.

For interfaces, I haven't given this a great deal of thought. In 
principle I don't think a static interface is especially useful, but I 
could be wrong about this. Nevertheless, it is not something I intend 
for this RFC, since even just static classes already have their 
detractors, and expanding its scope any further is probably placing it 
further in danger of rejection. So for now, the answer is also no, but 
static interfaces seem like a reasonable extension to this work if there 
is interest in future.

Cheers,
Bilge

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    <div class="moz-cite-prefix">Hi Ayesh,</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">On 24/06/2024 08:53, Ayesh Karunaratne
      wrote:<span style="white-space: pre-wrap">
</span><span style="white-space: pre-wrap">
</span></div>
    <blockquote type="cite"
cite="mid:CANLbj-qvn-BFfN8hEQRciUuT_qCiiPfyqc=YiL1Pw5+Oy-Ad4Q@mail.gmail.com">
      <pre class="moz-quote-pre" wrap=""> - Why is it a class-level flag and not an attribute (similar to the `#[Override]` attribute in PHP 8.3) ?
</pre>
    </blockquote>
    I believe Tim already answered this, and I understood his reasoning
    to be that keywords are used when they modify behaviour in a way
    that is meaningful for the consumer of that class. Or to put it
    another way, attributes are purely informational. For me personally,
    introducing an attribute never crossed my mind, and since we already
    have the keyword in the language performing a similar function in
    PHP, and other languages already, it seems nonsense to contemplate
    anything else.<span style="white-space: pre-wrap">
</span><span style="white-space: pre-wrap">
</span>
    <blockquote type="cite"
cite="mid:CANLbj-qvn-BFfN8hEQRciUuT_qCiiPfyqc=YiL1Pw5+Oy-Ad4Q@mail.gmail.com">
      <pre class="moz-quote-pre" wrap=""> - Can a subclass extend a static parent class without using the
`static` keyword in the subclass? This will avoid a lot of BC issues
if a library decides to declare classes as static.</pre>
    </blockquote>
    No, a static parent implies a static child, but implied or not, it
    must still be specified explicitly. I may need to clarify that in
    the RFC, so thanks for the question.<span
    style="white-space: pre-wrap">
</span>
    <blockquote type="cite"
cite="mid:CANLbj-qvn-BFfN8hEQRciUuT_qCiiPfyqc=YiL1Pw5+Oy-Ad4Q@mail.gmail.com">
      <pre class="moz-quote-pre" wrap=""> - Are there any opt-out mechanisms for subclasses?</pre>
    </blockquote>
    Not sure what you mean exactly, but if you mean, can a static
    subclass suddenly become non-static, the answer is no.<span
    style="white-space: pre-wrap"> Again thanks for the question, as this is also something I had no previously considered.
</span>
    <blockquote type="cite"
cite="mid:CANLbj-qvn-BFfN8hEQRciUuT_qCiiPfyqc=YiL1Pw5+Oy-Ad4Q@mail.gmail.com">
      <pre class="moz-quote-pre" wrap=""> - Can you mark interfaces, abstract classes, and Enums as static?
</pre>
    </blockquote>
    <p>It seems others avoided addressing this question, and honestly I
      was not really sure where to go with this one. What would it mean
      for an enum to be static? I thought the whole point was we can
      type a group of values, but static classes have no meaning within
      the type system, so I cannot see the application.</p>
    <p>As for abstract classes, the current version of the RFC (1.2) now
      declares static mutually exclusive with abstract, so the answer
      there is also no.</p>
    <p>For interfaces, I haven't given this a great deal of thought. In
      principle I don't think a static interface is especially useful,
      but I could be wrong about this. Nevertheless, it is not something
      I intend for this RFC, since even just static classes already have
      their detractors, and expanding its scope any further is probably
      placing it further in danger of rejection. So for now, the answer
      is also no, but static interfaces seem like a reasonable extension
      to this work if there is interest in future.</p>
    <p>Cheers,<br>
      Bilge<br>
    </p>
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