Function returning NotImplementedType cannot return NotImplemented if strict=True
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bug
topic-disallow-any
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- Python
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Description
Bug Report
A function returning NotImplementedType cannot return NotImplemented if strict=True.
(A clear and concise description of what the bug is.)
To Reproduce
from types import NotImplementedType
def foo() -> NotImplementedType:
return NotImplemented
Expected Behavior
Type checks even with --strict
Actual Behavior
main.py:4: error: Returning Any from function declared to return "_NotImplementedType" [no-any-return]
Found 1 error in 1 file (checked 1 source file)
Your Environment
- Mypy version used: 1.15.0
- Mypy command-line flags:
--strict - Mypy configuration options from
mypy.ini(and other config files): None - Python version used: 3.12
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
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- Open a pull request that references the issue number.
Research direction
Reproduce the reported example using NotImplementedType, NotImplemented, Python 3.12, and mypy 1.15.0 with --strict. Trace how the return type and the no-any-return diagnostic are handled, then verify that the example type-checks without the reported error.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100