Callable not deduced correctly

[nschloe]

I have a function add(x,y) that adds two floats, and that that the user can specify. If no custom function add is given, default_add is used. If it is given, I'm adding a little wrapper code to assert stuff:

from typing import Callable


def default_add(x: float, y: float, extra: float = 0) -> float:
    return x + y + extra


def wrap_add(
    add: Callable[[float, float], float],
) -> Callable[[float, float], float]:
    def _add(x: float, y: float) -> float:
        assert isinstance(x, (float, int))
        assert isinstance(y, (float, int))

        z = add(x, y)

        assert isinstance(z, (float, int))
        return z

    return _add


fun: Callable[[float, float], float] | None = None

fun2 = default_add if fun is None else wrap_add(fun)

fun2(3, 5)

Running mypy on the above gives

a.py:27: error: Cannot call function of unknown type  [operator]

When adding explicit typing to fun2,

fun2: Callable[[float, float], float] = default_add if fun is None else wrap_add(fun)

one incorrectly gets

a.py:25: error: Incompatible types in assignment (expression has type "function", variable has type "Callable[[float, float], float]") 

---

• Mypy version used: 1.8.0
• Mypy command-line flags: -
• Mypy configuration options from mypy.ini (and other config files): -
• Python version used: 3.11.6

[randolf-scholz]

Another example: mypy-playground

from collections.abc import Callable

def pprint(obj: object, repr_fn: Callable[..., str] = NotImplemented) -> str:
    repr_fn = (
        repr_fn   # expression has type "function", variable has type "Callable[..., str]"
        if repr_fn is not NotImplemented
        else repr
    )
    
    return repr_fn(obj)

[hauntsaninja]

Fixed in #17427