[ilevkivskyi]

Fixes python/mypy#2986

This is a simplest fix, and all other fixes will require complicated manual loading of collections (since it contains the actual class definitions for DefaultDict, Deque etc).

The problem is that if collections are not in checked modules, then DefaultDict, Deque etc. are automatically translated to Any thus potentially hiding some errors, see python/mypy#2986 for an example.

[JelleZijlstra]

Is it easy to fix this in mypy instead? It's a bit unfortunate to have to add this unused import to work around a mypy quirk.

[JelleZijlstra]

Could you add a reference to the mypy issue that makes clear why mypy needs this import? It's not really obvious from this comment why the import is necessary.

[ilevkivskyi]

OK, added the issue number.

[ilevkivskyi]

Is it easy to fix this in mypy instead?

I think no.

It's a bit unfortunate to have to add this unused import to work around a mypy quirk.

It's not a mypy quirk. All other type checkers also need to manually load collections (or do something similar). There is no way to know from typeshed how e.g. DefaultDict is defined (it is just TypeAlias(object)).

[JelleZijlstra]

Thanks for the explanation!