Regression in upcoming mypy 0.990

[arnimarj]

Hi. I was testing the upcoming mypy release and it seems to be emitting new warning for interface definitions:

import zope.interface


class IZomething(zope.interface.Interface):
	def Query(a: str, b: str) -> list[int]:
		pass

gives:

$ mypy --config=mypy.ini int.py 
int.py:5: error: Missing return statement  [empty-body]
Found 1 error in 1 file (checked 1 source file)

Replacing the function body with ellipses silences the warning. Perhaps that should be the preferred way to define interfaces moving forward?

[arnimarj]

This is probably caused by python/mypy#13729

[kedder]

It doesn't seem like ellipses help here (I'm getting the same error if I replace pass with ...). And clearly we don't want these errors for zope interface methods. Trying to figure out the workaround.

[kedder]

That particular issue was easy to work around by explicitly marking interface methods as "abstract". However now mypy complains about not being able to instantiate abstract classes when we do "adaptation pattern". And there seem to be some deeper issue in mypy that prevents a "nice" solution for this right now. Filed python/mypy#14106, waiting or some response.