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Date: Mon, 26 Aug 2024 11:23:02 +0100
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Subject: Re: [PHP-DEV] [RFC] Default expression
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From: bilge@scriptfusion.com (Bilge)

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On 26/08/2024 11:11, Andreas Leathley wrote:
> On 26.08.24 11:26, Bilge wrote:
>>
>> I would like to fix this if possible, because I think this should be 
>> valid, with emphasis on /if possible/, because it may be 
>> prohibitively complex. Will update later.
>>
> That would be a way to fix it, to basically make isset(default) a 
> possible check if there is no default, similar to an undefined 
> variable check. It would also recognize a default value of null as not 
> set in the same way, so one could not differentiate between null and 
> not defined, but that is in line with the language in general.

It would not be possible to write `isset(default)` because `isset()` 
does not operate on expressions. Similarly, it would not be possible to 
write `default === null ? ... : ...` because you would receive the same 
error as above. If we special-case null coalesce then it will literally 
only be possible to check with null coalesce.

As for feasibility, I definitely believe it is feasible. Though some may 
argue whether it's worth the trouble for this edge case, I would still 
like to implement it.

Cheers,
Bilge

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    <div class="moz-cite-prefix">On 26/08/2024 11:11, Andreas Leathley
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:a26f6cbf-f98e-42a8-8a9b-56209dc42a99@gmx.net">
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      <div class="moz-cite-prefix">On 26.08.24 11:26, Bilge wrote:<br>
      </div>
      <blockquote type="cite"
        cite="mid:a5e8faf3-e3d7-41c0-98b2-0999ee7444bb@scriptfusion.com">
        <meta http-equiv="Content-Type"
          content="text/html; charset=UTF-8">
        <p>I would like to fix this if possible, because I think this
          should be valid, with emphasis on <i>if possible</i>, because
          it may be prohibitively complex. Will update later.</p>
      </blockquote>
      That would be a way to fix it, to basically make isset(default) a
      possible check if there is no default, similar to an undefined
      variable check. It would also recognize a default value of null as
      not set in the same way, so one could not differentiate between
      null and not defined, but that is in line with the language in
      general.<br>
    </blockquote>
    <p>It would not be possible to write `isset(default)` because
      `isset()` does not operate on expressions. Similarly, it would not
      be possible to write `default === null ? ... : ...` because you
      would receive the same error as above. If we special-case null
      coalesce then it will literally only be possible to check with
      null coalesce.</p>
    <p>As for feasibility, I definitely believe it is feasible. Though
      some may argue whether it's worth the trouble for this edge case,
      I would still like to implement it.<br>
    </p>
    <p>Cheers,<br>
      Bilge<br>
    </p>
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