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main.py

import dataclasses
from functools import partial
from typing import TYPE_CHECKING, TypeAlias

if TYPE_CHECKING:
    from dataclasses import dataclass as frozen_nan_safe
else:
    def frozen_nan_safe(**kwargs):
        assert kwargs['frozen']
        return dataclasses.dataclass(**kwargs)
    
def test_frozen_decorator() -> None:
    @frozen_nan_safe(frozen=True)
    class Good:
        x: float

    nan = float('nan')
    reveal_type(Good)
    hash(Good(nan))
    assert Good(nan) == Good(nan)