Can't convert from Tuple of optional to Tuple of non-optional
Open
Nobody has claimed this yet.
false-positive
feature
priority-2-low
- Dominant language
- Python
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- 20.6k
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Description
Code:
from typing import Tuple, Optional
a: Tuple[Optional[int], Optional[int]] = (1, 1)
b: Tuple[int, int]
if a[0] is not None and a[1] is not None:
b = a
After that has error:
script.py:6: error: Incompatible types in assignment (expression has type "Tuple[Optional[int], Optional[int]]", variable has type "Tuple[int, int]")
Expected no error.
I have: mypy-0.770 and Python 3.7.7
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Research direction
Reproduce the reported error from script.py using mypy with the shown Tuple and Optional annotations. Investigate how mypy narrows tuple elements after the two None checks, and consider the work complete when the assignment to b is accepted without an incompatible-types error.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100