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Date: Mon, 26 Aug 2024 12:11:48 +0200
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Subject: Re: [PHP-DEV] [RFC] Default expression
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From: a.leathley@gmx.net (Andreas Leathley)

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On 26.08.24 11:26, Bilge wrote:
>
> Thanks for this question; I find this super interesting because it's
> something we haven't thought about yet. I must admit I completely
> overlooked that, whilst an interface /can/ require implementers to
> specify a default, in the case that they do not, it is still valid for
> implementations to selectively elect to provide one. Therefore I can
> append to your example the following case (I removed the `string`
> return type for now):
>
> class ZipCompression implements CompressionInterface
> {
> =C2=A0=C2=A0=C2=A0 public function compress(string $data, int $level)
> =C2=A0=C2=A0=C2=A0 {
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 var_dump($level);
> =C2=A0=C2=A0=C2=A0 }
> }
>
> new GzipCompression()->compress('', default ?? 6);
> new ZipCompression()->compress('', default ?? 6);
>
> In this case, we get the following output:
>
> int(4)
> Fatal error: Uncaught ValueError: Cannot pass default to required
> parameter 2 of ZipCompression::compress()
>
> 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.

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8">
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    <div class=3D"moz-cite-prefix">On 26.08.24 11:26, Bilge wrote:<br>
    </div>
    <blockquote type=3D"cite"
      cite=3D"mid:a5e8faf3-e3d7-41c0-98b2-0999ee7444bb@scriptfusion.com">
      <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3DUT=
F-8">
      <p>Thanks for this question; I find this super interesting because
        it's something we haven't thought about yet. I must admit I
        completely overlooked that, whilst an interface <i>can</i>
        require implementers to specify a default, in the case that they
        do not, it is still valid for implementations to selectively
        elect to provide one. Therefore I can append to your example the
        following case (I removed the `string` return type for now):</p>
      <p>class ZipCompression implements CompressionInterface<br>
        {<br>
        =C2=A0=C2=A0=C2=A0 public function compress(string $data, int $lev=
el)<br>
        =C2=A0=C2=A0=C2=A0 {<br>
        =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 var_dump($level);<br>
        =C2=A0=C2=A0=C2=A0 }<br>
        }</p>
      <p>new GzipCompression()-&gt;compress('', default ?? 6);<br>
        new ZipCompression()-&gt;compress('', default ?? 6);<br>
      </p>
      <p>In this case, we get the following output:</p>
      <p>int(4)<br>
        Fatal error: Uncaught ValueError: Cannot pass default to
        required parameter 2 of ZipCompression::compress()</p>
      <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>
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