subtype dict unpack
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bug
- Dominant language
- Python
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Description
Bug Report
To Reproduce
from typing import Dict
a: Dict[int, str] = {}
b: Dict[object, str] = {object(): 'a', 'lol': 'b', **a}
Expected Behavior
no error
Actual Behavior
confusing error message Argument 1 to "update" of "dict" has incompatible type "Dict[int, str]"; expected "Mapping[object, str]" even though update method was not used
Your Environment
- Mypy version used: 0.812
- Mypy command-line flags: none
- Mypy configuration options from
mypy.ini(and other config files): none - Python version used: 3.7.3
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
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- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the reported snippet with mypy 0.812 and trace how dictionary unpacking produces the diagnostic referring to dict.update. Confirm the fix by ensuring this example reports no error and add a regression test covering the unpacked Dict[int, str].
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