Allow Redefinitions of For Loop Iteration Variables
Open
Nobody has claimed this yet.
bug
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
Bug Report
MyPy has a flag --allow-redefinition to enable variable redefinition in limited circumstances. This doesn't seem to work with variables bound in a for loop iteration.
To Reproduce
for i in range(3):
i: str = str(i)
reveal_type(i)
def test(i: int):
i: str = str(i)
reveal_type(i)
Expected Behavior
Both cases are allowed.
Actual Behavior
MyPy throws an error only for line 2.
main.py:2: error: Name "i" already defined on line 1 [no-redef]
main.py:3: note: Revealed type is "builtins.int"
main.py:7: note: Revealed type is "builtins.str"
Found 1 error in 1 file (checked 1 source file)
Your Environment
MyPy Version v1.5.1
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running the linked mypy-play reproduction with MyPy 1.5.1, the Python 3.11 example, and --allow-redefinition. Trace how the for-loop variable and the function parameter are handled, then add coverage showing both redefinitions are accepted and the revealed types match the expected output.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100