Uses for Intersection in type hints

[ViktorSky]

The idea in proposing Intersection is to create type hints that support type transformations, since it is not possible to support this behavior without using inheritance.
Furthermore, it becomes much more complicated when trying to use it in overloads.

from typing import TypeVar, Protocol, TYPE_CHECKING, dataclass_transform

ModelT = TypeVar("ModelT", bound=type)

class CreatedModel(Protocol):
    def dump(self) -> str: ...

@dataclass_transform()
def create_model(cls: ModelT) -> ModelT:
    ...  # adding attributes
    return cls

class CustomerModel:
    id: int
    name: str

if TYPE_CHECKING:
    assert issubclass(CustomerModel, CreatedModel)

cls_type = CustomerModel  #  type[<subclass of CustomerModel and CreatedModel>]

In this case, I assume that this tool typing.Intersection exists. It should work similar to typing.Union, but the actual type meets the arguments of this as protocols

from typing import TypeVar, Protocol, dataclass_transform
from typing import Intersection  # not exist

ModelT = TypeVar("ModelT", bound=type)

class CreatedModel(Protocol):
    def dump(self) -> str: ...

@dataclass_transform()
def create_model(cls: ModelT) -> Intersection[ModelT, type[CreatedModel]]:
    ...
    return cls

@create_model
class CustomerModel:
    id: int
    name: str

This implementation would help the more efficient development of dynamic classes by linking with typevar so as not to lose a lot of information during its creation.

[JelleZijlstra]

Duplicate of #213.

See also https://github.com/CarliJoy/intersection_examples where there is work towards a PEP on Intersection.