Unknown `DefaultNamedArg` raises type incompatibility errors

[munael]

🐛 Bug Report

DefaultNamedArg may cause signature compatibility errors. Observed when a function has a default keyword argument in signature and is passed to be used as a function without that particular keyword argument.

To Reproduce

from typing import List, AnyStr
from glob import glob
import itertools as it
def expand_patterns(
        pats: List[AnyStr],
        sort=True
):
    paths = it.chain(map(glob, pats))
    # Argument 1 to "map" has incompatible type "Callable[[AnyStr, DefaultNamedArg(bool, 'recursive')], List[AnyStr]]"; expected "Callable[[AnyStr], List[AnyStr]]"
    if sort:
        paths = sorted(paths)
    return paths

Expected Behavior

Not sure if this ought to happen, but I'd expect a function like foo(x: int, y='y') to be peacefully passable to a function expecting Callable[[int], Any].

Actual Behavior

# Argument 1 to "map" has incompatible type "Callable[[AnyStr, DefaultNamedArg(bool, 'recursive')], List[AnyStr]]"; expected "Callable[[AnyStr], List[AnyStr]]"

Your Environment

• Mypy version used: 0.782
• Mypy command-line flags: Default of VSCode
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.7.7
• Operating system and version: Windows 10, 2004

[JelleZijlstra]

This still fails (https://mypy-play.net/?mypy=latest&python=3.10&gist=dcb917f24b1c11b45813c0e4181c2be2):

main.py:8: error: Argument 1 to "map" has incompatible type "Callable[[AnyStr, DefaultNamedArg(Optional[Union[str, bytes, PathLike[str], PathLike[bytes]]], 'root_dir'), DefaultNamedArg(Optional[int], 'dir_fd'), DefaultNamedArg(bool, 'recursive')], List[AnyStr]]"; expected "Callable[[str], List[AnyStr]]"
main.py:8: error: Argument 1 to "map" has incompatible type "Callable[[AnyStr, DefaultNamedArg(Optional[Union[str, bytes, PathLike[str], PathLike[bytes]]], 'root_dir'), DefaultNamedArg(Optional[int], 'dir_fd'), DefaultNamedArg(bool, 'recursive')], List[AnyStr]]"; expected "Callable[[bytes], List[AnyStr]]"
main.py:11: error: Incompatible types in assignment (expression has type "List[List[AnyStr]]", variable has type "chain[List[AnyStr]]")
Found 3 errors in 1 file (checked 1 source file)