mypy doesn't catch inheritance of outer class
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bug
topic-runtime-semantics
- Dominant language
- Python
- Stars
- 20.6k
- Forks
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- PR merge metrics
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Description
Bug Report
Inheriting from an outer class raises NameError at runtime, but mypy doesn't catch this.
To Reproduce
class Foo:
class Bar(Foo):
pass
Expected Behavior
Actual Behavior
Success: no issues found in 1 source file
Your Environment
- Mypy version used: 1.14.0
- Python version used: 3.13
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 with the nested-class reproducer in the issue and confirm the runtime NameError alongside mypy's current output. Trace the type-checking path that analyzes class bases, add a regression test for inheriting from the outer class, and verify that mypy reports an error for the example.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100