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Date: Thu, 16 Mar 2023 17:14:40 -0500
To: "php internals" <internals@lists.php.net>
Content-Type: text/plain
Subject: Re: [PHP-DEV] Brainstorming idea: inline syntax for lexical (captured)
 variables
From: larry@garfieldtech.com ("Larry Garfield")

On Thu, Mar 16, 2023, at 5:06 PM, Rowan Tommins wrote:
> On 16/03/2023 17:59, Nicolas Grekas wrote:
>> We could define the "use" as declaring + setting the properties before 
>> the constructor is called, if any.
>> But I'm also fine making both constructs conflict: when there is a 
>> constructor, the boilerplate saved by the "use" becomes really low.
>> No strong opinion either. There could be other factors to consider.
>
>
> The main advantage of generating an actual constructor is that no change 
> is needed to the shared object initialization code, which could be 
> complex and even have performance impact. The only new logic would be in 
> compiling the class entry and putting the arguments into the "new 
> class(...)" statement.
>
> The more I think about it, the more I'm leaning to just blocking custom 
> constructors, and saying you can either have the use() short-hand, or 
> you can have custom initialization. Additional functionality can always 
> be added in later if someone comes up with a clean implementation and a 
> good use case.

Wouldn't the functionality described boil down to essentially just materializing into a few extra lines in the constructor?  At least to my ignorant non-engine brain it seems straightforward to have this:

$a = 1;
$b = 2;
$c = 3;

$o = new class ($a, $b) use ($c) {
  public function __construct(private int $a, private int $b) {}
  public function something() {}
}

Desugar to this:

$c = class ($a, $b) use ($c) {
  private $c;
  public function __construct(private int $a, private int $b) {
    $this->c = 3;  // By value only, so this should be fine?
  }
  public function something() {}
}

--Larry Garfield