Inheriting from two data classes causes error Definition of "__match_args__" in base class "A" is incompatible with definition in base class "B"

[dcermak]

Bug Report

When creating a derived class that inherits from two data classes, mypy will immediately flag the derived class with Definition of "__match_args__" in base class "A" is incompatible with definition in base class "B"

To Reproduce

1. Create the following file

from dataclasses import dataclass

@dataclass
class A:
    prop_a: str

@dataclass
class B:
    prop_b: bool

class Derived(A, B):
    pass

2. Run mypy . and observe the error:

test.py:11: error: Cannot override final attribute "__match_args__" (previously declared in base class "B")
test.py:11: error: Cannot override writable attribute "__match_args__" with a final one
test.py:11: error: Definition of "__match_args__" in base class "A" is incompatible with definition in base class "B"
Found 3 errors in 1 file (checked 1 source file)

Expected Behavior

Given that I did not set __match_args__ myself makes this error really hard to understand. I would have expected no such error to occur, especially as the code should work for older Python versions that don't support pattern matching yet.

Your Environment

• Mypy version used: 0.940
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.10
• Operating system and version: Linux, Fedora 35

[AlexWaygood]

Looks like the same bug as #12008