Annotation of `Callable` and `function`

Bug Report

I am experiencing the following problem: I have a function that takes a list of functions with a set default argument. I am annotating this variable with List[Callable] which leads to the following error when I supply a defined list of functions as default argument.

In code, I am e.g. doing this:

from typing import Callable


def fun(x):
    return x


def fun2(x, y):
    return 2 * x + y


default_functions = [fun, fun2]


def fun3(func: list[Callable] = default_functions):
    return func


def fun4(func: list[Callable] = [fun, fun2]):
    return func

Expected Behavior

I would have expected that both function definitions are correct: the functions fun1, fun2 are of type Callable and putting them into a list should fulfifl the type annotation.

Actual Behavior

Running mypy on this leads to:

scripts/mypy_callable.py:15: error: Incompatible default for argument "func" (default has type "List[function]", argument has type "List[Callable[..., Any]]")  [assignment]
Found 1 error in 1 file (checked 1 source file)

which refers to fun3.

So, there are three things I don't understand here:

• Why is there a difference between fun3 and fun4?
• As far as I understand, function is a subtype of Callable so why wouldn't a default value of type List[function] be acceptable to mypy here?
• If I accept this behavior, how would I annotate the func argument with List[function]? Where do I get function from? As far as I can see, it is not part of standard Python nor in the typing library.

Your Environment

(mypy version 0.991, python 3.10.8)

• Mypy version used: 0.991
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.10.8

Riproduci l'esempio dell'issue usando scripts/mypy_callable.py e il comando mypy indicato senza flags. Inizia tracciando il modo in cui mypy inferisce i tipi di default_functions e dell'elenco inline; il lavoro è completato quando la discrepanza viene risolta con un comportamento corrispondente oppure le aspettative vengono documentate chiaramente.