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Date: Tue, 25 Apr 2023 19:00:12 +0200
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To: Larry Garfield <larry@garfieldtech.com>
Cc: php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [Discussion] Callable types via Interfaces
From: nicolas.grekas+php@gmail.com (Nicolas Grekas)

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Hi all,

https://wiki.php.net/rfc/allow_casting_closures_into_single-method_interface_implementations
>
> https://wiki.php.net/rfc/allow-closures-to-declare-interfaces-they-implement
> https://wiki.php.net/rfc/structural-typing-for-closures


Thanks Larry for the nice introduction to those ideas.

Personally, I feel like going with adding Closure::castTo() might provide
the most immediate benefit. I expanded the rationale on the corresponding
RFC and added more examples. I'd appreciate it if all of you reading could
have another look to see if that helps to better understand the proposal.

strtr(...)->castTo(TranslatableInterface::class) is one example of RFC #1
function ($message, $parameters) implements TranslatableInterface is RFC #2

Both RFCs nicely combine together to cover many cases of typed callabled.

Then RFC#3 is a bit more adventurous (according to our understanding) but
still desirable as it's essentially about allowing the engine to
tentatively call castTo() from RFC#1 when a closure is passed as argument
while an interface is expected.

We're now wondering if we should start spending time on prototype
implementations for #1 and/or #2, and #3 in this order. Should we consider
a preliminary vote on the topic?

Nicolas

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