Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:122727
Content-Type: multipart/alternative;
 boundary="------------ET2UXd6sZ97ZoEqTkQghzHW2"
Message-ID: <bea2860c-8e28-43cf-a73c-157dbe907316@seld.be>
Date: Fri, 22 Mar 2024 14:06:20 +0100
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PHP-DEV] Proposal: AS assertions
Content-Language: fr
To: "Rowan Tommins [IMSoP]" <imsop.php@rwec.co.uk>, internals@lists.php.net
References: <CAPzBOBMGe=kWWiJYGLG02qxh+2Pe5yTqodhGtAE3LjdAPmkQUw@mail.gmail.com>
 <efbffe5a-f57a-42e4-8e0c-b25ab2c441fc@rwec.co.uk>
 <CAPzBOBM4b5c=hWgcj6uBgK3Lb65X56T-bhGHVGhma_YnCCJuoQ@mail.gmail.com>
 <CAPzBOBM8dmP5e-N4WXgM+7xbBYx7b=1DyPyJuV5O6QHX2F2s0w@mail.gmail.com>
 <3F78A125-1946-42E2-A4F5-A2B282BE2107@rwec.co.uk>
 <CAPzBOBPDVE-xtQoFUOXchwNAo_iJTGs=RKcnoq1mOtKF70eeLA@mail.gmail.com>
 <2d7ec203-6e80-445c-94f4-d29ef58743b1@rwec.co.uk>
 <CAPzBOBOqNT17CRiDsw78GH647xM09z4Y4HpSvM55RXoS-BWfKA@mail.gmail.com>
 <becdbf66-be58-4b4e-a0be-52a9c78f7f26@seld.be>
 <7d53f2e4-46f3-46f1-89b0-6e1d3b0b2e32@app.fastmail.com>
In-Reply-To: <7d53f2e4-46f3-46f1-89b0-6e1d3b0b2e32@app.fastmail.com>
From: j.boggiano@seld.be (Jordi Boggiano)

This is a multi-part message in MIME format.
--------------ET2UXd6sZ97ZoEqTkQghzHW2
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit

On 2024-03-22 10:46, Rowan Tommins [IMSoP] wrote:
> On Fri, 22 Mar 2024, at 08:17, Jordi Boggiano wrote:
>> We perhaps could make sure that as does not throw if used with `??`, 
>> or that `??` catches the type error and returns the right-hand 
>> expression instead:
>>
>> So to do a nullable typecast you would do:
>>
>>     $a as int|float ?? null
>>
>
> While this limits the impact to only expressions combining as with ?? 
> it still has the same fundamental problem: you can't meaningfully use 
> it with a nullable type.
>
>
> As a concrete example, imagine you have an optional $description 
> parameter, and want to ensure any non-null values are converted to 
> string, but keep null unchanged.
>
> At first sight, it looks like you could write this:
>
> $descString = $description as string|null ?? (string)$description;
>
> But this won't work - the ?? swallows the null and turns it into an 
> empty string, which isn't what you wanted. You need some syntax that 
> catches the TypeError, but preserves the null:
>
> $descString = $description as string|null else (string)$description;
> // or
> $descString = $description as string|null catch (string)$description;
> // or
> $descString = $description as string|null default (string)$description;
>
>
> I actually think there are quite a lot of scenarios where that idiom 
> would be useful:
>
> $optionalExpiryDateTime = $expiry as ?DateTimeInterface else new 
> DateTimeImmutable($expiry);
> $optionalUnixTimestamp = $time as ?int else strotime((string)$time);
> $optionalUnicodeName = $name as ?UnicodeString else new UnicodeString( 
> $name );
> etc

Yeah I think this looks great actually, minus the confusing bits about 
|null which is in reality yes probably rarely useful in a "as" cast.

as that throws + default to catch it👍🏻

Best,
Jordi

-- 
Jordi Boggiano
@seldaek -https://seld.be

--------------ET2UXd6sZ97ZoEqTkQghzHW2
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 8bit

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body>
    <div class="moz-cite-prefix">On 2024-03-22 10:46, Rowan Tommins
      [IMSoP] wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:7d53f2e4-46f3-46f1-89b0-6e1d3b0b2e32@app.fastmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <title></title>
      <style type="text/css">p.MsoNormal,p.MsoNoSpacing{margin:0}</style>
      <div>On Fri, 22 Mar 2024, at 08:17, Jordi Boggiano wrote:<br>
      </div>
      <blockquote type="cite" id="qt" style="">
        <div class="qt-moz-cite-prefix">We perhaps could make sure that
          as does not throw if used with `??`, or that `??` catches the
          type error and returns the right-hand expression instead:<br>
        </div>
        <p>So to do a nullable typecast you would do:<br>
        </p>
        <p>    $a as int|float ?? null<br>
        </p>
      </blockquote>
      <div><br>
      </div>
      <div>While this limits the impact to only expressions combining as
        with ?? it still has the same fundamental problem: you can't
        meaningfully use it with a nullable type.<br>
      </div>
      <div><br>
      </div>
      <div><br>
      </div>
      <div>As a concrete example, imagine you have an optional
        $description parameter, and want to ensure any non-null values
        are converted to string, but keep null unchanged.<br>
      </div>
      <div><br>
      </div>
      <div>At first sight, it looks like you could write this:<br>
      </div>
      <div><br>
      </div>
      <div>$descString = $description as string|null ??
        (string)$description;<br>
      </div>
      <div><br>
      </div>
      <div>But this won't work - the ?? swallows the null and turns it
        into an empty string, which isn't what you wanted. You need some
        syntax that catches the TypeError, but preserves the null:<br>
      </div>
      <div><br>
      </div>
      <div>$descString = $description as string|null else
        (string)$description;<br>
      </div>
      <div>// or<br>
      </div>
      <div>$descString = $description as string|null catch
        (string)$description;<br>
      </div>
      <div>// or<br>
      </div>
      <div>$descString = $description as string|null default
        (string)$description;<br>
      </div>
      <div><br>
      </div>
      <div><br>
      </div>
      <div>I actually think there are quite a lot of scenarios where
        that idiom would be useful:<br>
      </div>
      <div><br>
      </div>
      <div>$optionalExpiryDateTime = $expiry as ?DateTimeInterface else
        new DateTimeImmutable($expiry);<br>
      </div>
      <div>$optionalUnixTimestamp = $time as ?int else
        strotime((string)$time);<br>
      </div>
      <div>$optionalUnicodeName = $name as ?UnicodeString else new
        UnicodeString( $name );<br>
      </div>
      <div>etc<br>
      </div>
    </blockquote>
    <p>Yeah I think this looks great actually, minus the confusing bits
      about |null which is in reality yes probably rarely useful in a
      "as" cast.</p>
    <p>as that throws + default to catch it👍🏻<br>
    </p>
    <p>Best,<br>
      Jordi<br>
    </p>
    <pre class="moz-signature" cols="72">-- 
Jordi Boggiano
@seldaek - <a class="moz-txt-link-freetext" href="https://seld.be">https://seld.be</a></pre>
  </body>
</html>

--------------ET2UXd6sZ97ZoEqTkQghzHW2--