“至少一个参数是 X 类型”的类型注释

Question

我正在尝试使用 重载 使可变参数函数的返回类型以某种方式取决于其参数的类型。具体来说，当且仅当其参数的any是X类型时，我希望返回类型为X。

考虑以下最小示例：

from typing import overload

class Safe:
    pass

class Dangerous:
    pass

@overload
def combine(*args: Safe) -> Safe: ...

@overload
def combine(*args: Safe | Dangerous) -> Safe | Dangerous: ...

def combine(*args: Safe | Dangerous) -> Safe | Dangerous:
    if all(isinstance(arg, Safe) for arg in args):
        return Safe()
    else:
        return Dangerous()

reveal_type(combine())
reveal_type(combine(Safe()))
reveal_type(combine(Dangerous()))
reveal_type(combine(Safe(), Safe()))
reveal_type(combine(Safe(), Dangerous()))

这输出

example.py:21: note: Revealed type is "example.Safe"
example.py:22: note: Revealed type is "example.Safe"
example.py:23: note: Revealed type is "Union[example.Safe, example.Dangerous]"
example.py:24: note: Revealed type is "example.Safe"
example.py:25: note: Revealed type is "Union[example.Safe, example.Dangerous]"
Success: no issues found in 1 source file

我想设置一些东西，例如，

combine(Dangerous())

和

combine(Safe(), Dangerous())

的推断类型是

Dangerous

而不是

Safe | Dangerous

。将第二个重载的返回类型更改为

Dangerous

会产生错误：

example.py:10: error: Overloaded function signatures 1 and 2 overlap with incompatible return types  [misc]
example.py:21: note: Revealed type is "example.Safe"
example.py:22: note: Revealed type is "example.Safe"
example.py:23: note: Revealed type is "example.Dangerous"
example.py:24: note: Revealed type is "example.Safe"
example.py:25: note: Revealed type is "example.Dangerous"
Found 1 error in 1 file (checked 1 source file)

因此，我似乎需要一种方法来注释第二个重载以明确声明至少一个它的参数是

Dangerous

。有没有办法做到这一点？

Answer 1

使用 PyRight，您的解决方案确实有效。而mypy也可以用简单的方式强行接受

# type: ignore

：

@overload
def combine(*args: Safe) -> Safe: ...  # type: ignore

@overload
def combine(*args: Safe | Dangerous) -> Dangerous: ...

def combine(*args: Safe | Dangerous) -> Safe | Dangerous:
    if all(isinstance(arg, Safe) for arg in args):
        return Safe()
    else:
        return Dangerous()


reveal_type(combine())  # Safe
reveal_type(combine(Safe()))  # Safe
reveal_type(combine(Dangerous()))  # Dangerous
reveal_type(combine(Safe(), Safe()))  # Safe
reveal_type(combine(Safe(), Dangerous()))  # Dangerous