[Variadic] Specifying the list shape for variadic handler implementations

[lisachenko]

Currently, for variadic syntax it is possible to define the type or a shape of individual element, which is typical case and well-supported, however in some cases, variadic arguments are typed individually, representing the concrete list shape.

I'm looking for a solution to define the exact list shape for such variadic functions/methods.

See an example from playground: https://phpstan.org/r/a9cc25b5-dc7f-47f9-9718-53e62fda6e61

[ondrejmirtes]

Hi, I've been thinking about this and I think the OOP design of HookInterface / concrete hook doesn't work well.

There's no value to HookInterface::handle. You're typing mixed ...$rawArguments which means that any narrower parameter type in an implementation violates Liskov Substitution Principle (contravariance).

Presumably you have ...$rawArguments in ReadDimensionHook / WriteDimensionHook only because HookInterface is also variadic.

Personaly I'd get rid of HookInterface and type the handle methods normally, with three to four native parameters.

[lisachenko]

The problem here, that I can not dictate the Hook interface, it is dictated by the Zend Engine and how it emulates the callback via FFI trampoline, each callback is just a thin wrapper, which usually do CData <=> Native PHP value tricks behind like this https://github.com/lisachenko/z-engine/blob/8.4/src/ClassExtension/Hook/DoOperationHook.php#L79-L107 - this will give PHP developers normal variable and not internal C structures.

To hide the complexity of Zend Engine internals, I decided to declare all handlers defined as variadic and each concrete handler takes the CData, effectively I can put handle(CData ...$rawArguments): CData, but this creates again a lot of problem with typing and static checks as CData type represents effectively any custom structure inside, that's why I open php/php-src#23229 to propose changes in this area as well.

I understand why you proposing to drop the interface, but it is hard to do it without automation of low-level mappings. Thus all these games around object/list shapes...

Anyway, thank you for the feedback, you confirmed that there is no easy way to declare it now. At least I know this fact now )

[ondrejmirtes]

Currently it's not, PHPStan will check each variadic argument against the same type. You can't declare any difference either, it'd need a new syntax, maybe a new PHPDoc tag.

But you can open a feature request to track this in the future 😊

[lisachenko]

converted to the feature request.

Looks like it can be supported if phpStan will check the presence of "..." symbol in the phpDoc - if present, then given type in docBlock specifies the single item type and it is repeated for all arguments; if "..." symbol is not specified, then phpDoc specifies the type/shape of all arguments, eg list<object> $variadicArgs, array<object> $variadicArgs, list{int, string, string, string} $variadicArgs, etc

#15077