Regression caused by #5565

#5565 causes the following code to fail with `Name 'x' already defined`, while it is perfectly valid:
```python
class C:
    def __init__(self, x: int) -> None:
        self.x = x
    @property
    def x(self) -> int: ...
    @x.setter
    def x(self, x: int) -> None: ...
```