class inferred as abstract when it isn't.

[randolf-scholz]

Code sample in pyright playground

from abc import abstractmethod
from typing import Protocol

class Dataset[T_co](Protocol):
    r"""Protocol for Dataset class."""

    INFO_URL: str = NotImplemented
    r"""Web address containing documentational information about the dataset."""

    @abstractmethod
    def download(self) -> None: ...
    @abstractmethod
    def load(self) -> T_co: ...

    # mixin methods
    def info(self) -> None:
        if self.INFO_URL is NotImplemented:
            raise NotImplementedError("No INFO_URL provided for this dataset!")
        print(f"See {self.INFO_URL}")

class MyDataset(Dataset[int]):
    def download(self) -> None:
        print("Downloading")

    def load(self) -> int:
        return 42

MyDataset()  # ❌ Cannot instantiate abstract class "MyDataset"

It seems pyright infers that info is abstract due to the two lines:

        if self.INFO_URL is NotImplemented:
            raise NotImplementedError("No INFO_URL provided for this dataset!")

if NotImplementedError is replaced with another type of Exception, info is no longer inferred as abstract.

[randolf-scholz]

Moreover, it seems this affects only Protocol types. If the base class is changes to abc.ABC or nothing, then it also disappears.

[erictraut]

This is addressed in pyright 1.1.370