--check-untyped-defs required to check any imported class init

[kyprifog]

Note: if you are reporting a wrong signature of a function or a class in
the standard library, then the typeshed tracker is better suited
for this report: https://github.com/python/typeshed/issues

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Bug?

Using the default example found here for classes:
https://mypy.readthedocs.io/en/stable/class_basics.html#class-basics

I get the same result, however if I import A into another class "--check-untyped-defs" is required to detect the same errors.

[emmatyping]

Could you clarify what you mean by "Import A into another class"? Also you probably are running into https://mypy.readthedocs.io/en/stable/common_issues.html#no-errors-reported-for-obviously-wrong-code

[kyprifog]

Sorry my wording was bad, I meant, if A is invoked from an import. I think I found the issue though, I had:

[mypy]
ignore_missing_imports = True

Which I intended to apply to only external exports, I didn't realize this applied to all imports within the same project so it was treating it like Any. Removing this line I got

b/b.py:1: error: Cannot find implementation or library stub for module named 'a'

which I presume means it was being treated as Any