abstract `__init__` signature of `abc.ABC` doesn't get type checked

[bluenote10]

Bug Report

If an abstract base class has a __init__ that is annotated as @abc.abstractmethod, the signature should be verified for clients implementing the __init__. This does not seem to be the case.

To Reproduce

import abc

class Base(abc.ABC):
    @abc.abstractmethod
    def __init__(self, a: int):
        ...

class Client(Base):
    def __init__(self, a: str):
        ...

Expected Behavior

A type error in the child's __init__ because it violates the signature. This works for regular methods, i.e., replacing both __init__ by e.g. foo errors with:

main.py:10: error: Argument 1 of "foo" is incompatible with supertype "Base"; supertype defines the argument type as "int"  [override]
main.py:10: note: This violates the Liskov substitution principle
main.py:10: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides

Actual Behavior

mypy doesn't detect the type error.

Your Environment

• Mypy version used: 1.4.0
• Mypy command-line flags: --strict
• Mypy configuration options from mypy.ini (and other config files): (nothing, just using the playground)
• Python version used: 3.11