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我无法让 pylance 或 mypy 对键入通用状态函数感到满意。如果我对状态机进行硬编码（不使用通用基类），我不会收到任何错误。在我的实际实现中，泛型类也不是抽象类，但我遇到了同样的问题，所以问题与此无关。

这是代码。请注意，这里的实现与我的状态机所做的无关。我刚刚创建了一些显示相同问题的最小的东西。我还努力让类型检查快乐​​，让特定的状态函数指定流的结尾（例如state_done），而不是寻找 value None。

from __future__ import annotations
from abc import ABC, abstractmethod
from typing import TypeVar, Generic, Optional, Callable
import random


_T = TypeVar("_T")
StateFunc = Optional[Callable[[_T], Optional["StateFunc"]]]


class GenericMachine(Generic[_T], ABC):
    def __init__(self):
        self._state: StateFunc[_T]

    def run(self) -> None:
        while self._state is not None:
            self._state = self._state(self.get_next_event())

    @abstractmethod
    def get_next_event(self) -> _T:
        pass


class Catch(GenericMachine[float]):
    _MyStateFunc = StateFunc[float]

    def __init__(self):
        print("person has ball")
        self._state: Catch._MyStateFunc = self._state_person_with_ball  # ERROR 1

    def get_next_event(self) -> float:
        return random.random()

    def _state_person_with_ball(self, r: float) -> Catch._MyStateFunc:
        if r < 0.2:
            return None
        print("ball in air")
        return self._state_ball_in_air  # ERROR 2

    def _state_ball_in_air(self, r: float) -> Catch._MyStateFunc:
        print("dog has ball")
        return self._state_dog_with_ball  # ERROR 2

    def _state_dog_with_ball(self, r: float) -> Catch._MyStateFunc:
        if r < 0.2:
            return None
        print("person has ball")
        return self._state_person_with_ball  # ERROR 2


if __name__ == "__main__":
    Catch().run()

编辑：我意识到 mypy 不会超过递归类型定义。当我刚刚声明StateFunc返回一个Callable.

Pylance 为 ERROR 1 报告以下内容（通过 VS Code）：

Cannot assign member "_state" for type "Catch"
  Expression of type "(r: float) -> (_p0: float) -> StateFunc | None | None" cannot be assigned to member "_state" of class "Catch"
    Type "(r: float) -> (_p0: float) -> StateFunc | None | None" cannot be assigned to type "(_p0: float) -> StateFunc | None | None"
      Type "(r: float) -> (_p0: float) -> StateFunc | None | None" cannot be assigned to type "(_p0: float) -> StateFunc | None"
      Type cannot be assigned to type "None"
        Function return type "(_p0: float) -> StateFunc | None | None" is incompatible with type "StateFunc | None"
          Type "(_p0: float) -> StateFunc | None | None" cannot be assigned to type "StateFunc | None"PylancereportGeneralTypeIssues
(variable) _state: (r: float) -> Unknown

它为错误 2 报告以下内容（通过 VS 代码）：

Expression of type "(r: float) -> (_p0: float) -> StateFunc | None | None" cannot be assigned to return type "(_p0: float) -> StateFunc | None | None"
  Type "(r: float) -> (_p0: float) -> StateFunc | None | None" cannot be assigned to type "(_p0: float) -> StateFunc | None | None"
    Type "(r: float) -> (_p0: float) -> StateFunc | None | None" cannot be assigned to type "(_p0: float) -> StateFunc | None"
    Type cannot be assigned to type "None"
      Function return type "(_p0: float) -> StateFunc | None | None" is incompatible with type "StateFunc | None"
        Type "(_p0: float) -> StateFunc | None | None" cannot be assigned to type "StateFunc | None"
          Type "(_p0: float) -> StateFunc | None" cannot be assigned to type "StateFunc | None"PylancereportGeneralTypeIssues
(parameter) self: Catch

知道如何让 Pylance 开心吗？

更新：如果我将 StateFunc 定义如下，问题就会消失：

StateFunc = Optional[Callable[[_T], Any]]

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