Re: Type casting syntax

On Mon, Jul 12, 2021, at 9:26 AM, Levi Morrison via internals wrote: > > What are the use cases for integrated object to object (ie, class to class) conversion in > > PHP? Rust's type system is a very different beast, so its casting logic makes more sense > > there. I'm not entirely clear on what the use case is in PHP. When would that be superior to > > "just write an asFoo() method and move on with life"? > > > > Scalar conversion I can see, but every time someone suggests adding siblings to > > __toString(), there's major pushback. > > > > --Larry Garfield > > > > -- > > PHP Internals - PHP Runtime Development Mailing List > > To unsubscribe, visit: https://www.php.net/unsub.php > > > > The features I was referring to are not casting; casting does exist in > Rust but this is not it. Rather, it's a generic way to convert > objects. It's nice to have a standard way to do it, instead of every > project doing something bespoke. It also can enable some use cases > that aren't relevant in PHP (yet) such as taking any generic type > which can be converted into a T, because you only want to do that > transformation conditionally on something else. So, like David suggested, some standardized version of $foo->as($type), which then returns an instance of $type? I... don't think I've ever done that often enough to justify a standard feature for it. When have you run into it? That also seems quite different from what Max is talking about: On Mon, Jul 12, 2021, at 9:54 AM, Max Semenik wrote: > I was thinking of something akin to many compiled languages' approach of > "consider this expression is now of that type, and throw an exception if > it's not". An example of this approach from Benjamin's proposal of old^ > > $service = (EmailService) $diContainer->get('email.service'); > > Instead of > > /** @var EmailService $service */ > $service = $diContainer->get('email.service'); > if (!$service instanceof EmailService) { > throw new TypeError('Expected instance of EmailService, ...'); > } Hm, that's a different creature. I... would be probably OK with something in that direction, though I wouldn't work on it myself. I think what you're describing here is more of a type assertion. "Assert that this variable is of type X, otherwise bail." So, some kind of non-disableable (or maybe disableable?) shorthand for assert($foo instanceof Bar). --Larry Garfield