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eliegoudout opened this issue Jun 8, 2025 · 3 comments · Fixed by #19258
Closed

Missing line number error report #19257

eliegoudout opened this issue Jun 8, 2025 · 3 comments · Fixed by #19258
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@brianschubert
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bug mypy got something wrong topic-error-reporting How we report errors

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@eliegoudout
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eliegoudout commented Jun 8, 2025 •
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Hi there,

I wanted to know if someone already had this: I have error with no line number, so I don't really know how to debug them. For example, you can this failing pipeline which shows

paramclasses/paramclasses.py: error: Incompatible types in assignment (expression has type "object", variable has type "list[object]")  [assignment]
paramclasses/paramclasses.py: error: Incompatible types in assignment (expression has type "object", variable has type "dict[str, object]")  [assignment]

It's not "global", as before I had errors with and without line numbers

paramclasses/paramclasses.py: error: Incompatible types in assignment (expression has type "object", variable has type "list[Any]")  [assignment]
paramclasses/paramclasses.py: error: Incompatible types in assignment (expression has type "object", variable has type "dict[Any, Any]")  [assignment]
paramclasses/paramclasses.py:272: error: "type" has no attribute "__post_init__"; maybe "__init__"?  [attr-defined]
paramclasses/paramclasses.py:528: error: Need type annotation for "args" (hint: "args: list[<type>] = ...")  [var-annotated]
...

Thanks in advance!
Élie
@eliegoudout eliegoudout added the bug mypy got something wrong label Jun 8, 2025
@eliegoudout
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eliegoudout commented Jun 8, 2025 •
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After invstigation, I know it comes from the following code:

https://github.com/eliegoudout/paramclasses/blob/902eb276f3046457b9f09ef23a42e2e1ecb897e9/paramclasses/paramclasses.py#L539-L548

Of course, I understand the errors, but I don't really know why there are no lines!

Note however that

# type: ignore[assignment]  # Not statically checked

does not silence the errors!

@brianschubert
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brianschubert commented Jun 8, 2025 •
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Simplified reproducer:

a: list[int]
b: str
(b,) = (*a,)

outputs:

main.py: error: Incompatible types in assignment (expression has type "int", variable has type "str")  [assignment]

@brianschubert brianschubert self-assigned this Jun 8, 2025
@brianschubert brianschubert mentioned this issue Jun 8, 2025
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@brianschubert brianschubert added the topic-error-reporting How we report errors label Jun 8, 2025
@eliegoudout
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eliegoudout commented Jun 9, 2025 •
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Thanks for finding a MWE. I think you could also add the # type: ignore[assignment] to complete it (after double-checking, i'm currently unable to, writing from my phone).

pull bot pushed a commit to Dareh123/mypy that referenced this issue Jun 10, 2025
@brianschubert
Fix missing error context for unpacking assignment involving star exp…
8667022 
…ression (python#19258)

Fixes python#19257
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Fix missing error context for unpacking assignment involving star expression brianschubert/mypy
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