PHPStan callable definitions do not support custom mapped types

[jiripudil]

Version: dev-master

Bug Description

The callable definitions introduced in #216 fail to support custom mapped types:

class MappedValues {
    public string $name;
}

$form = new Nette\Forms\Form();
$form–>addText('name', 'Name');
$form->setMappedType(MappedValues::class);
$form->onSuccess[] = function (Form $form, MappedValues $values) {};

produces

Array (array<(callable(Nette\Forms\Form, array): void)|(callable(Nette\Forms\Form, Nette\Utils\ArrayHash): void)>) does not accept Closure(Nette\Forms\Form, MappedValues): void.

I don't know how the variance works there, but neither adding callable(Form, object) nor class MappedValues extends ArrayHash seemed to help. Perhaps @ondrejmirtes or @JanTvrdik could chime in please?

[ondrejmirtes]

Hi, there's no way to support this. Form definitions and onSuccess are usually in different files... We should probably revert it to mixed. /cc @adaamz

[adaamz]

What about array and second variant for object? mixed is too wide...
Also we should somehow fix variant with only one parameter (Form $form): void

[ondrejmirtes]

It will complain about dangerous calls on object on level 6+.

[ondrejmirtes]

Also we should somehow fix variant with only one parameter (Form $form): void

Does not have to be fixed. It's fine to pass callable with a single parameter somewhere multiple arguments are passed.

[jiripudil]

What do you mean,by "revert it to mixed"? Isn't it the case that an array of callable(Form, object) (or callable(Form, mixed) for that matter) will never accept a Closure(Form, SpecificClass) because of LSP? The second argument type is not contravariant, so the closure is not a subtype of the callable type 🤔

[JanTvrdik]

• callable(Form, mixed) should accept Closure(Form, SpecificClass) because of gradual typing,
• callable(Form, object) should not accept Closure(Form, SpecificClass)

[jiripudil]

callable(Form, mixed) should accept

Then there must be some issue there because, apparently, it does not

[JanTvrdik]

@jiripudil Yes, that's a bug on this line https://github.com/phpstan/phpstan/blob/4415f4c5d897359433cdcbc1576d3be7bb2757ec/src/Type/CallableType.php#L70.

[ondrejmirtes]

Should be fixed: phpstan/phpstan#2170

[dg]

What is the final consensus? mixed or object? (#223)

[jiripudil]

I believe mixed since object would not work as discussed above. I'll amend the PR

[ondrejmirtes]

FYI #216 (comment)