error in argument when using chained function-call
Open
Nobody has claimed this yet.
bug
false-positive
priority-1-normal
topic-overloads
topic-type-variables
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
- PR merge metrics
- PR metrics pending
Description
Example:
dct = {"": ""}
# ok
trans = str.maketrans(dct)
"".translate(trans)
# err
"".translate(str.maketrans(dct))
- What is the actual behavior/output?
maketrans.py:8: error: Argument 1 to "maketrans" of "str" has incompatible type "Dict[str, str]"; expected "Union[Dict[int, Union[int, str, None]], Dict[str, Union[int, str, None]], Dict[Union[str, int], Union[int, str, None]]]"
- What is the behavior/output you expect?
No error.
- What are the versions of mypy and Python you are using?
I tested both mypy 0.610 and mypy 0.620+dev-0ca6bf9ce63439a1e8bcc4dec80ef12f8414cb87 with Python 3.6.5; behavior is identical.
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 chained-call example in maketrans.py and reproduce it using Python 3.6.5 with the reported mypy versions. Compare the separate and nested str.maketrans calls; done means the nested form no longer reports the incompatible Dict[str, str] argument 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
- 35/100