Incorrect __post_init__ order when KW_ONLY used

from dataclasses import dataclass, InitVar, KW_ONLY


@dataclass
class A:
    _: KW_ONLY
    x: InitVar[int]

    def __post_init__(self, x: int) -> None:
        pass


@dataclass
class C(A):
    y: InitVar[str]

    def __post_init__(self, x: int, y: str) -> None:  # Correct order.
        super().__post_init__(x)

gives

a.py:19: error: Argument 2 of "__post_init__" is incompatible with supertype "dataclass"; supertype defines the argument type as "str"  [override]
        def __post_init__(self, x: int, y: str) -> None:
                                ^~~~~~
a.py:19: error: Argument 3 of "__post_init__" is incompatible with supertype "dataclass"; supertype defines the argument type as "int"  [override]
        def __post_init__(self, x: int, y: str) -> None:

首先复现报告中的 Python 示例，并确认涉及 post_init 的两个 override 错误。然后跟踪 mypy 对 KW_ONLY 和 InitVar 的 dataclass 处理，以确定参数顺序是在哪里推导出来的。当示例能够在没有这些错误的情况下通过类型检查，同时保留所展示的 post_init 顺序时，即表示完成。