Message416846
Hi,
According to https://peps.python.org/pep-0544/#explicitly-declaring-implementation it should be possible to explicitly inherit from Protocols. This however breaks the dataclass constructor when using the @property decorator in the protocol, see this example:
```python
from typing import Protocol
from dataclasses import dataclass
class SomeProtocol(Protocol):
@property
def some_value(self) -> str: ...
@dataclass
class SomeDataclasss(SomeProtocol):
some_value: str
if __name__ == '__main__':
a = SomeDataclasss(some_value="value") # this crashes with AttributeError: can't set attribute 'some_value'
```
The pattern of @property in the protocol is one taken from the mypy docs (see https://mypy.readthedocs.io/en/stable/protocols.html#recursive-protocols for example).
When removing the explicit inheritiance mypy also correctly typechecks the dataclass implementation when doing something like, only the explicit inheritance seems to fail in python
```python
a: SomeProtocol = SomeDataclass()
``` |
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Date |
User |
Action |
Args |
2022-04-06 08:41:16 | Germandrummer92 | set | recipients:
+ Germandrummer92 |
2022-04-06 08:41:16 | Germandrummer92 | set | messageid: <1649234476.2.0.0289467757353.issue47237@roundup.psfhosted.org> |
2022-04-06 08:41:16 | Germandrummer92 | link | issue47237 messages |
2022-04-06 08:41:15 | Germandrummer92 | create | |
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