Support Type[] type with delegate

[sobolevn]

Currently, we cannot express something like:

@some.instance(Type[MyClass], delegate=MyDelegate)
def _some_type_myclass(instance: Type[MyClass]) -> int: ...

We can only dispatch on type and that's it.
I think that this feature is useful.

Related #264
Related #274

[thepabloaguilar]

In fact we cannot express the example below without delegate too since Type is a generic thing:

@some.instance(Type[MyClass])
def _some_type_myclass(instance: Type[MyClass]) -> int: ...

What's the goal of this issue, enable Type in .instance or enable Type just for delegated typeclasses?

[sobolevn]

Yes, you are right! It should be:

@some.instance(delegate=MyTypeDelegate)
def _some_type_myclass(instance: Type[MyClass]) -> int: ...

[thepabloaguilar]

So, what we need to do here? Like, the delegated classes are something that the users pass and that have the highest priority when we're evaluating the values

[sobolevn]

We need to make sure that the example above works and type-checks 🙂

[thepabloaguilar]

I'd like to propose that we provide some delegate classes. Like this one that will check a Type because in order to do that check the users must know how to use get_origin and get_args from typing that's tricky sometimes!

P.S.: I made @example.instance(Type[MyClass]) works and all unit tests passed! Maybe we can add .type decorator

[sobolevn]

@thepabloaguilar great idea! Please, create a new issue for that! 👍