Why does PyCharm not accept my type hint for an empty list?

Looking at PEP 484, specifically the section on type comments (the precursor to variable annotations) this does indeed seem like a bug with PyCharm’s checker.

Quoting from the PEP:

In non-stub code, there is a similar special case:

from typing import IO

stream = None  # type: IO[str]

Type checkers should not complain about this (despite the value None not matching the given type), nor should they change the inferred type to Optional[...] (despite the rule that does this for annotated arguments with a default value of None ). The assumption here is that other code will ensure that the variable is given a value of the proper type, and all uses can assume that the variable has the given type.

So, in a similar fashion, type-checkers (as mypy currently does), should not complain about the fact that the initializing value you provide doesn’t strictly match the annotation.