Wrong number of arguments for callable

[vikigenius]

I posted a stackoverflow question about this, and then came to realize that this is a bug on mypy: https://stackoverflow.com/questions/60981471/python-function-object-as-a-class-attribute

Reproducing here for completeness

Consider two alternative definitions of the class Replace

import re
from dataclasses import dataclass
from typing import Callable, Match


@dataclass
class Replace1(object):
    """Dataclass that stores info about replacement protocol."""

    replstr: str = ''
    predicate: Callable[[str], bool] = lambda string: True

    def __call__(self, match: Match[str]) -> str:
        """Callable that returns the replacement given a match."""
        matched: str = match.group(0)
        return match.expand(self.replstr) if self.predicate(matched) else matched # This is a complaint in self.predicate(matched)

@dataclass
class Replace2(object):
    """Dataclass that stores info about replacement protocol."""

    replstr: str = ''
    predicate: Callable[['Replace2', str], bool] = lambda repl, string: True

    def __call__(self, match: Match[str]) -> str:
        """Callable that returns the replacement given a match."""
        matched: str = match.group(0)
        return match.expand(self.replstr) if self.predicate(matched) else matched

Both Replace1 and Replace2 seem to work the exact same way

r1 = Replace1(predicate=lambda x: len(x.split()) > 5)
r2 = Replace2(predicate=lambda x: len(x.split()) > 5) # This is a complaint in lambda


pattern = re.compile(r'(?:\w+\s*)+')

match1 = re.match(pattern, 'This will prevail')
match2 = re.match(pattern, 'This is too long and will be destroyed')

assert r1(match1) == 'This will prevail'
assert r2(match1) == 'This will prevail'
assert r1(match2) == ''
assert r2(match2) == ''

However mypy seems to complain about self.predicate(matched) having too many arguments in Replace1. And also seems to be complaining about Replace2(predicate=lambda x: len(x.split()) > 5) not having enough arguments.

What exactly is happening? How do I get the desired behavior and not have mypy complain ?

[JelleZijlstra]

This sounds like a variant of #5485.

[msullivan]

I think I agree that this is #5485.