mypy doesn't get error with typed `dict(*{'A': 10})` while PVM gets error
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Description
*Memo:
- python test.py
- mypy test.py
- Python 3.14.0
- mypy 1.19.1
PVM gets the error with typed and untyped dict(*{'A': 10}) as shown below:
v1 = dict(*{'A': 10}) # Error
v2: dict[str, int] = dict(*{'A': 10}) # Error
ValueError: dictionary update sequence element #0 has length 1; 2 is required
But, mypy gets the error only for untyped dict(*{'A': 10}) while typed dict(*{'A': 10}) doesn't get error as shown below:
v1 = dict(*{'A': 10}) # Error
v2: dict[str, int] = dict(*{'A': 10}) # No error
error: Need type annotation for "v1" (hint: "v1: dict[, ] = ...")
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Research direction
Start by reproducing the examples in test.py with Python 3.14.0 and mypy 1.19.1, comparing the typed and untyped dict(*{'A': 10}) cases. Trace the type-checking path for the annotated assignment and add a regression test that captures the expected diagnostic for the runtime-invalid call.
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Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 35/100