import dataclasses
from dataclasses import dataclass, replace
from typing import Any, ClassVar, Generic, Protocol, Self, TypeVar


class DataclassInstance(Protocol):
    __dataclass_fields__: ClassVar[dict[str, dataclasses.Field[Any]]]


T = TypeVar('T')
@dataclass
class X(Generic[T]):
    a: int

    def f(self) -> Self:
        reveal_type(self)  # Self@X[T@X]
        assert isinstance(self, DataclassInstance)
        reveal_type(self)  # X[T@X]
        return replace(self, a=1)  # Error, can't return X.