Confusing error when subclassing `var.__class__`
Open
Nobody has claimed this yet.
bug
topic-runtime-semantics
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
Consider this example:
x: int = 1
class X(x.__class__):
# Name "x.__class__" is not defined
# Class cannot subclass "__class__" (has type "Any")
pass
Name "x.__class__" is not defined is confusing. Why x.__class__ is considered a name? I suggest removing this error in this case.
My Environment
mypy 0.961 (compiled: no)- no command-line flags, no config file
CPython 3.10.4- Windows 10
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
Use the Python example in the issue as the reproducer and trace how the type checker handles an attribute expression used as a class base. Confirm the diagnostic currently reported for x.__class__, then adjust the behavior so this confusing name error is removed in that case and verify the example no longer produces it.
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
- 35/100