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Hang on some type hints #18928
Description
Bug Report
mypy hangs and appears to have entered an infinite loop on some function argument type hints.
To Reproduce
The following code hangs mypy version 1.15.0 on my machine:
def normal_dist_intersection(m1: float | np.ndarray, m2: float | np.ndarray, s1: float | np.ndarray, s2: float | np.ndarray):
return (m2*s1*s1 - s2 * (m1*s2 + s1*np.sqrt((m1 - m2)**2 + 2*(s1*s1 - s2*s2) * np.log(s1/s2)))) / (s1*s1 - s2*s2)The following code works as expected. Note that the only difference is the removal of the last float type hint.
def normal_dist_intersection(m1: float | np.ndarray, m2: float | np.ndarray, s1: float | np.ndarray, s2: np.ndarray):
return (m2*s1*s1 - s2 * (m1*s2 + s1*np.sqrt((m1 - m2)**2 + 2*(s1*s1 - s2*s2) * np.log(s1/s2)))) / (s1*s1 - s2*s2)Your Environment
- Mypy version used: 1.15.0
- Mypy command-line flags: python -m mypy some/path/to/file/under/test.py
- Mypy configuration options from mypy.ini (and other config files): None
- Python version used: 3.11.11
Activity
brianschubert commented on Apr 16, 2025
Thanks! Looks similar to #14978
sterliakov commented on Apr 22, 2025
It's exactly #14978. For every overload signature of a numpy function (such as ndarray.__add__ with whopping 17 overloads of which 9 are relevant), we accept all arguments. Nest 6 such arguments, and we check simple operations $9^6 \approx 500,000$ times. Nest 10, and we'll be checking that forever.