This code does not work. It defines __eq__ method like this:

def __eq__(self: T, other: T) -> bool: pass

But on this example

from dataclasses import dataclass

@dataclass
class A: pass

reveal_type(A.__eq__)

latest version of mypy outputs

test.py:6: note: Revealed type is 'def (builtins.object, builtins.object) -> builtins.bool'

And it is right, I think dataclasses shouldn't override __eq__ signature of base object type and we should remove this broken code completely.