Issue initialising dataclass with getters and setters

When using mypy with a dataclass that includes getters and setters it throws an error. It returns Name 'byr' already defined on line 5.

To Reproduce

To reproduce use mypy with this script:

@dataclass
class Passport:
    byr: int

    @property
    def byr(self) -> int:
        return self._byr

    @byr.setter
    def byr(self, value) -> None:
        if int(value) < 1920 or int(value) > 2002:
            raise Exception("Birth year must be between 1920 and 2002")
        self._byr = int(value)

Expected Behavior

I would have expected it to accept this, as this seems to be a standard way to handle getters and setters.

Your Environment

• Mypy command-line flags: python -m mypy my.py
• Python version used: 3.9.0
• Operating system and version:

Comienza con la dataclass proporcionada y ejecuta python -m mypy my.py para reproducir el error de nombre duplicado. Traza cómo se analizan las dataclasses y los property getters/setters, y después añade una prueba de regresión que demuestre que este patrón se acepta sin el error.