There should be an inverse of `Type`

Specifically, it would be nice if there was a keyword Instance such that Instance[Type[_T]] is equivalent to _T

I'm thinking about this mostly in the context of working with metaclasses.

Suppose I have a class with a class method that creates an instance of the class written so it can be reused by subclasses. This can be typed in the following way:

_ThingInstance = TypeVar('_ThingInstance', bound='Thing')

class Thing():

    @classmethod
    def make_new(cls: Type[_ThingInstance]) -> _ThingInstance:
        return cls()

And this is automatically usable by subclasses.

What I want is an Instance type such that I can correctly type the same logic defined within a metaclass like so:

_ThingClass = TypeVar('_ThingClass', bound='MetaThing')

class MetaThing(type):

  def make_new(cls: _ThingClass) -> Instance[_ThingClass]:
      return cls()

As far as I can tell, there's no way to correctly annotate this

Start from the proposed Instance[_ThingClass] annotation and compare it with the shown Type[_ThingInstance] pattern. Define how the inverse should behave for metaclass methods and verify the examples with type-checking coverage; done means the requested annotations are accepted with the intended inferred instance types.