小编Nun*_*nsy的帖子

当尝试使用类型的 TypeVar 来启用具有返回类型的泛型时，我遇到了 mypy 错误，即bound在比较字典的类型和函数的预期返回类型时未考虑参数。

下面是我面临的情况的一个例子：

from typing import Dict, List, Type, TypeVar


class Bird:
    def call(self):
        print(self.sound)


class Chicken(Bird):
    def __init__(self):
        self.sound = "bok bok"


class Owl(Bird):
    def __init__(self):
        self.sound = "hoot hoot"


T = TypeVar("T", bound=Bird)


class Instantiator:
    def __init__(self, birds: List[Type[Bird]]):
        self._bird_map: Dict[Type[Bird], Bird] = {}
        for bird in birds:
            self._bird_map[bird] = bird()

    def get_bird(self, bird_type: Type[T]) -> T:
        return self._bird_map[bird_type]

运行 mypy 验证器将显示：temp.py:29: error: Incompatible return value type (got "Bird", expected "T")

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