Bounding a TypeVar to a Protocol #7212
Description
Are you reporting a bug, or opening a feature request?
Feature request.
Please insert below the code you are checking with mypy,
or a mock-up repro if the source is private. We would appreciate
if you try to simplify your case to a minimal repro.
class Example(Protocol):
sentence: List[str]
T = TypeVar('T', bound=Example)
class Dataset(Generic[T]):
....
class ConcreteExample(NamedTuple):
sentence: List[str]
others: Any
class ConcreteDataset(Dataset[ConcreteExample]):
....What is the actual behavior/output?
On the line defining ConcreteDataset, mypy gives an error that the type ConcreteExample is not a subtype of Example.
What is the behavior/output you expect?
mypy is correct in the error, but I would like a way to bound the TypeVar to a Protocol such that classes satisfying the protocol would not have to subclass it. For instance, in the previous example, it is not possible to subclass Example because ConcreteExample is a NamedTuple. I also feel that it's against the original motivation of Protocol to require some class to subclass it.