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Subject: Re: [PHP-DEV] RFC: Anonymous Class Lexical Scope
From: dmitry@zend.com (Dmitry Stogov)



On 04/19/2016 05:18 PM, Nikita Popov wrote:
> On Tue, Apr 19, 2016 at 3:31 PM, Joe Watkins <pthreads@pthreads.org> wrote:
>
>> Morning Internals,
>>
>>      Please review the following RFC:
>>
>>      https://wiki.php.net/rfc/lexical-anon
>>
>>      A look at the patch from those of you that do that would be good :)
>>
> Hey Joe,
>
> The syntax and semantics proposed in this RFC don't sit quite well with me.
> Especially the fact that a use($foo) on the class is then used as
> $this->foo in methods is non-intuitive to me, as it differs from how the
> same syntax behaves on closures. I'd like to suggest an alternative syntax:
>
> $foo = 42;
> return new class {
>      private $bar = $foo;
>      public function getBar() { return $this->bar; }
> }

This syntax is definitely better, less magic and more powerful.

>
> That is, allow properties inside the anonymous class to be initialized
> based on values from the surrounding scope. This is more explicit (clearly
> shows that a property is being created), it allows explicit control over
> the visibility and, depending on implementation, might be more flexible
> with regards to the values it accepts. It probably doesn't make sense to
> restrict this to specific expressions, so all of
>
> return new class {
>      private $a = $var;
>      private $b = $obj->prop;
>      private $d = $obj->prop ?? 'default';
>      // ...
> }
>
> could be fine.

Is this for anonymous classes only?
Only for property default values or something else?

Also, instead of lexical scoping, we may use generic approach.

return new class<A=&$var,B=$obj->prop,C=$obj->prop ?? 'default'> {
     private $a = A;
     private $b = B;
     private $d = C;
};

But good design of generics would take a lot of ...

Thanks. Dmitry.

>
> Thanks,
> Nikita
>