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Date: Mon, 26 Aug 2024 14:18:04 +0100
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Subject: Re: [PHP-DEV] [RFC] Default expression
To: Jordi Boggiano <j.boggiano@seld.be>,
 "internals@lists.php.net" <internals@lists.php.net>
References: <0c8ed5d6-5507-4c41-8d7f-05d14ba8aa4c@scriptfusion.com>
 <4086414f-f8cb-4209-a127-0de19f065a47@seld.be>
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From: bilge@scriptfusion.com (Bilge)

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On 26/08/2024 12:55, Jordi Boggiano wrote:
> Hey Bilge,
Hi :)
>
> On 24.08.2024 18:49, Bilge wrote:
>> New RFC just dropped: https://wiki.php.net/rfc/default_expression. I 
>> think some of you might enjoy this one. Hit me with any feedback. 
>
> Great work overall, I'm all for it and even though it's not something 
> I saw myself using a whole lot, the json_encode example sold me on it 
> being more useful than I initially thought.
Thanks! I concede, this is one of those tools for your toolbox that you 
will seldom reach for, but comes in very handy whenever you do.
>
> One question (sorry if someone already asked, I scanned the thread but 
> it is getting long..):
I don't blame you. I'll summarise the main takeaways in the RFC later.
>
> Taking this example from the RFC:
>
>     function g($p = null) {
>         f($p ?? default);
>     }
>
> Could you go one step further and use default by default but still 
> allow null to be passed in?
>
>     function g($p = default) {
>         f($p);
>     }
>
No. The RFC has a very specific and singular focus in this regard: to 
permit `default` /only/ in function call contexts. That is, although 
`default` is a valid expression, it cannot be passed around or stored in 
a variable. Since this is a function definition, rather than a call, 
this will result in a compiler error. The specific error we get in this 
case is: "Fatal error: Constant expression contains invalid operations".

Cheers,
Bilge

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    <div class="moz-cite-prefix">On 26/08/2024 12:55, Jordi Boggiano
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:4086414f-f8cb-4209-a127-0de19f065a47@seld.be">Hey Bilge,
      <br>
    </blockquote>
    Hi :)<br>
    <blockquote type="cite"
      cite="mid:4086414f-f8cb-4209-a127-0de19f065a47@seld.be">
      <br>
      On 24.08.2024 18:49, Bilge wrote:
      <br>
      <blockquote type="cite">New RFC just dropped:
        <a class="moz-txt-link-freetext" href="https://wiki.php.net/rfc/default_expression">https://wiki.php.net/rfc/default_expression</a>. I think some of you
        might enjoy this one. Hit me with any feedback. </blockquote>
      <br>
      Great work overall, I'm all for it and even though it's not
      something I saw myself using a whole lot, the json_encode example
      sold me on it being more useful than I initially thought.
      <br>
    </blockquote>
    Thanks! I concede, this is one of those tools for your toolbox that
    you will seldom reach for, but comes in very handy whenever you do.<br>
    <blockquote type="cite"
      cite="mid:4086414f-f8cb-4209-a127-0de19f065a47@seld.be">
      <br>
      One question (sorry if someone already asked, I scanned the thread
      but it is getting long..):
      <br>
    </blockquote>
    I don't blame you. I'll summarise the main takeaways in the RFC
    later.<br>
    <blockquote type="cite"
      cite="mid:4086414f-f8cb-4209-a127-0de19f065a47@seld.be">
      <br>
      Taking this example from the RFC:
      <br>
      <br>
          function g($p = null) {
      <br>
              f($p ?? default);
      <br>
          }
      <br>
      <br>
      Could you go one step further and use default by default but still
      allow null to be passed in?
      <br>
      <br>
          function g($p = default) {
      <br>
              f($p);
      <br>
          }
      <br>
      <br>
    </blockquote>
    <p>No. The RFC has a very specific and singular focus in this
      regard: to permit `default` <i>only</i> in function call
      contexts. That is, although `default` is a valid expression, it
      cannot be passed around or stored in a variable. Since this is a
      function definition, rather than a call, this will result in a
      compiler error. The specific error we get in this case is: "Fatal
      error: Constant expression contains invalid operations".</p>
    <p>Cheers,<br>
      Bilge<br>
    </p>
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