Bug report

typing.get_type_hints() works for Callable[[], None] from the typing module, but not collections.abc. This is the standard way to annotate a callable which takes no arguments, and the generic types from typing should behave identically to those in collections.abc.

import collections.abc
import typing

def f1(x: typing.Callable[[], None]):
    pass

def f2(x: collections.abc.Callable[[], None]):
    pass

assert "x" in typing.get_type_hints(f1)
typing.get_type_hints(f2)  # Raises TypeError!

Your environment

CPython 3.11.0a7 (and I believe back to a3), found via CI for Hypothesis, and reproduced in Ubuntu/WSL2 locally.
I'm skipping that test for now, and will re-enable when this is fixed.