--warn-annotation-comments

[srittau]

I think having a linter option warning about old-style type comment annotations, instead of PEP 3107/526 annotations, would be useful. (With the obvious exception of # type: ignore comments.) This is potentially something that would make more sense in linters like flake8, but mypy also feels like a natural place where such an option could exist.

[ilevkivskyi]

Note that there are tools that can clean this up in a single pass, like https://github.com/ilevkivskyi/com2ann.

On one hand, this is very simple to implement, on the other hand this will add an option that will soon be irrelevant.