changed the title Type ignores comments erroneously marked as unused by dmypy Type ignore comments erroneously marked as unused by dmypy

meshy mentioned this pull request

The problem this solved has been addressed in another way, so we don't
need to do this re-analysis any more in order to fix the bug we've been
chasing.

This change is a partial revert of "Fix disappearing errors when
re-running dmypy check" from a few commits back.

There is currently a misbehaviour where "type: ignore" comments are
erroneously marked as unused in re-runs of dmypy. There are also cases
where errors disappear on the re-run.

As far as I can tell, this only happens in modules which contain an
import that we don't know how to type (such as a module which does not
exist), and a submodule which is unused.

There was a lot of commenting and investigation on this PR, but I hope
that the committed tests and fixes illustrate and address the issue.

Related to #9655

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Co-authored-by: David Seddon <david@seddonym.me>
Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Co-authored-by: Ivan Levkivskyi <levkivskyi@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>