[New-bugs-announce] [issue45081] dataclasses that inherit from Protocol subclasses have wrong __init__

[Julian Fortune]

New submission from Julian Fortune <juliandfortune at gmail.com>:

I believe [`bpo-44806: Fix __init__ in subclasses of protocols`](https://github.com/python/cpython/pull/27545) has caused a regression when using a Dataclass.

In Python `3.9.7`, a `dataclass` that inherits from a subclass of `typing.Protocol` (i.e., a user-defined protocol), does not have the correct `__init__`.

### Demonstration

```python
from dataclasses import dataclass
from typing import Protocol

class P(Protocol):
    pass

@dataclass
class B(P):
    value: str

print(B("test"))
```
In `3.9.7`:
```shell
Traceback (most recent call last):
  File "test.py", line 11, in <module>
    print(B("test"))
TypeError: B() takes no arguments
```
In `3.9.6`:
```shell
B(value='test')
```

### Affected Projects

- [dbt](https://github.com/dbt-labs/dbt/issues/3843)

----------
components: Library (Lib)
messages: 400868
nosy: julianfortune
priority: normal
severity: normal
status: open
title: dataclasses that inherit from Protocol subclasses have wrong __init__
type: behavior
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45081>
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