1.6.1 > 1.7.0 and 1.7.1 regression in for "broken" ``dataclasses``
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Description
Bug Report
When type checking the following code the output changes depending on whether you use 1.6.0 or 1.7.1.
To Reproduce
from dataclasses import dataclass
@dataclass(frozen=True)
class A:
attr_one: int
attr_two: int | None
@dataclass(frozen=True)
class B(A):
attr_two = None
instance = B(attr_one=1)
print(instance.attr_two)
Playground: https://mypy-play.net/?mypy=1.7.0&python=3.11&gist=f74740e7a7ef6bf0c9f88175a988aed5
The code is likely not doing what the author expects it to do, but the new message is wrong as attr_two can be referenced and is certainly not an instance of B.
Expected Behavior
main.py:15: error: Missing positional argument "attr_two" in call to "B" [call-arg]
Found 1 error in 1 file (checked 1 source file)
Actual Behavior
main.py:15: error: Missing positional argument "attr_two" in call to "B" [call-arg]
main.py:16: error: "B" not callable [operator]
Found 2 errors in 1 file (checked 1 source file)
Your Environment
master branch on Playground.
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 by reproducing the dataclass example in the issue or its linked mypy-playground configuration, comparing the reported diagnostics across the affected versions. Trace the dataclass handling that produces the erroneous "B not callable" message; done means the example reports only the missing attr_two argument as expected.
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