mypy accepts tuple[int] etc.

[ilevkivskyi]

mypy currently accepts

tuple[int], list[int], dict[int, str]

while all of those fail at runtime. I think those should be flagged as errors.

[JukkaL]

This is an old bug, but I couldn't find an existing issue. #999 is closely related -- fixing either of these issues would likely make the remaining issue trivial to fix.