no error when method has a keyword argument but no positional arguments
Open
Nobody has claimed this yet.
bug
priority-2-low
topic-runtime-semantics
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
class A:
def __init__(*, self) -> None:
...
a = A() # runtime error - TypeError: A.__init__() takes 0 positional arguments but 1 was given
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 Python reproducer and linked mypy-play example to inspect how mypy checks a method declared with only a keyword argument. Trace the constructor argument-checking entry point and add a regression test for the shown class; done means mypy reports the invalid definition or call consistently with the runtime TypeError.
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
- 35/100