Treating all numpy floating and complex types as interchangeable in overloads

Bug Report

I am trying to specify that a function takes either an array of np.floating or np.complexfloating, and returns an array of the same type, using overloads. However, it seems like mypy is currently treating floating and complexfloating as completely interchangeable, instead of floating being a more specific type than complexfloating. As shown below, it also treats other numpy floating/complex types as interchangeable, e.g. np.float32 and np.complex128.

To Reproduce

from __future__ import annotations

from typing import overload

import numpy as np
from numpy.typing import NDArray


@overload
def test_type1(a: NDArray[np.floating]) -> NDArray[np.floating]:  ...
@overload
def test_type1(a: NDArray[np.complexfloating]) -> NDArray[np.complexfloating]: ...
def test_type1(a: NDArray[np.floating] | NDArray[np.complexfloating]) -> NDArray[np.floating] | NDArray[np.complexfloating]:
    return a


@overload
def test_type2(a: NDArray[np.complexfloating]) -> NDArray[np.complexfloating]: ...
@overload
def test_type2(a: NDArray[np.floating]) -> NDArray[np.floating]:  ...
def test_type2(a: NDArray[np.floating] | NDArray[np.complexfloating]) -> NDArray[np.floating] | NDArray[np.complexfloating]:
    return a


@overload
def test_type3(a: np.floating) -> np.floating:  ...
@overload
def test_type3(a: np.complexfloating) -> np.complexfloating: ...
def test_type3(a: np.floating | np.complexfloating) -> np.floating | np.complexfloating:
    return a


@overload
def test_type4(a: np.complexfloating) -> np.floating:  ...
@overload
def test_type4(a: np.floating) -> np.floating: ...
def test_type4(a: np.floating | np.complexfloating) -> np.floating | np.complexfloating:
    return a


@overload
def test_type5(a: np.float32) -> np.float32:  ...
@overload
def test_type5(a: np.complex128) -> np.complex128: ...
def test_type5(a: np.float32 | np.complex128) -> np.float32 | np.complex128:
    return a


@overload
def test_type6(a: float) -> float: ...
@overload
def test_type6(a: complex) -> float:  ...
def test_type6(a: float | complex) -> float | complex:
    # the only one that passes mypy
    return a

Actual Behavior

In version 1.15.0 the code above passes mypy. In version 1.16.0 and later, it gives:

mypy_test.py:12: error: Overloaded function signature 2 will never be matched: signature 1's parameter type(s) are the same or broader [overload-cannot-match] mypy_test.py:20: error: Overloaded function signature 2 will never be matched: signature 1's parameter type(s) are the same or broader [overload-cannot-match] mypy_test.py:28: error: Overloaded function signature 2 will never be matched: signature 1's parameter type(s) are the same or broader [overload-cannot-match] mypy_test.py:36: error: Overloaded function signature 2 will never be matched: signature 1's parameter type(s) are the same or broader [overload-cannot-match] mypy_test.py:44: error: Overloaded function signature 2 will never be matched: signature 1's parameter type(s) are the same or broader [overload-cannot-match]

Expected Behavior

The errors for line 20 and 36 (test_type2 and test_type4) are correct errors as I understand the intended function of this warning. test_type6 correctly passes, consistent with the documented behavior of this check. However, the other 3 functions should pass with no warning, but are generating one.

Your Environment

I have tested and get the errors with mypy versions 1.16.0 and 1.18.2. The numpy version is 2.2.6 and python 3.13.7.

Tái hiện các chẩn đoán đã được báo cáo từ mypy_test.py bằng các ví dụ overload được cung cấp và so sánh hành vi giữa các phiên bản mypy được đề cập. Theo dõi bước kiểm tra overload-cannot-match, sau đó xác minh rằng test_type1, test_type3 và test_type5 đều vượt qua, trong khi test_type2 và test_type4 tiếp tục báo lỗi.