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Date: Tue, 27 Aug 2024 19:36:54 +0100
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Subject: Re: [PHP-DEV] [RFC] Default expression
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

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On 27/08/2024 16:03, John Bafford wrote:
> I'm not sure this could even work at all. The "default" parameter to
> gettype() isn't the default value of the third parameter to
> json_encode(). It's the default value of the first parameter to
> gettype(). Which would probably fail, since gettype()'s first parameter
> doesn't have a default. I suppose this could be solved by specifying an
> offset or label (e.g. as with `continue 2` in a nested loop), but that
> would just make it even harder to read.


Ah, good catch. So without a pattern-matching "default is int", I'm not 
sure how you'd even achieve that safety.


There are a few other examples on this thread that contain the same 
mistake, such as MWOP's:

class A {
     public function __construct(private LogInterface $logger = new 
DefaultLogger()) { }
}

class ProxiedLogger implements LogInterface { ... }

$a = new A(new ProxyLogger(default));

The "default" wouldn't look anything up in A::__construct, only in 
ProxyLogger::__construct. To pass the default out to any kind of 
function, you'd have to write some contorted expression like this:

$a = new A( $default=default && false ?: new ProxyLogger($default) );

That's even further into Obfuscated Code Contest territory than "default 
=> default", and further reduces the reasonable use cases for expressions.


-- 
Rowan Tommins
[IMSoP]

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    <div class="moz-cite-prefix">On 27/08/2024 16:03, John Bafford
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:A8CD76C6-7409-4C78-BEFD-6782059FD9B1@zort.net">
      <pre>I'm not sure this could even work at all. The "default" parameter to 
gettype() isn't the default value of the third parameter to 
json_encode(). It's the default value of the first parameter to 
gettype(). Which would probably fail, since gettype()'s first parameter 
doesn't have a default. I suppose this could be solved by specifying an 
offset or label (e.g. as with `continue 2` in a nested loop), but that 
would just make it even harder to read.</pre>
    </blockquote>
    <p><br>
    </p>
    <p>Ah, good catch. So without a pattern-matching "default is int",
      I'm not sure how you'd even achieve that safety.<br>
    </p>
    <p><br>
    </p>
    <p>There are a few other examples on this thread that contain the
      same mistake, such as MWOP's:</p>
    <p>class A {<br>
          public function __construct(private LogInterface $logger = new
      DefaultLogger()) { } <br>
      }<br>
      <br>
      class ProxiedLogger implements LogInterface { ... }<br>
      <br>
      $a = new A(new ProxyLogger(default));<br>
      <br>
    </p>
    <p>The "default" wouldn't look anything up in A::__construct, only
      in ProxyLogger::__construct. To pass the default out to any kind
      of function, you'd have to write some contorted expression like
      this:<br>
    </p>
    <p>$a = new A( $default=default &amp;&amp; false ?: new
      ProxyLogger($default) );</p>
    <p>That's even further into Obfuscated Code Contest territory than
      "default =&gt; default", and further reduces the reasonable use
      cases for expressions.</p>
    <p><br>
    </p>
    <pre class="moz-signature" cols="72">-- 
Rowan Tommins
[IMSoP]</pre>
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