Currently the following code will infer type Any for Foo().bar, although it should infer type str:

from werkzeug.utils import cached_property

class Foo:
    @cached_property
    def bar(self) -> str:
        return ""

reveal_type(Foo().bar)

Making class cached_property generic over the value solves this problem and corrects the type of a few fields like Request.base_url. I have a PR ready for this that actually removes a few instances of # type: ignore in werkzeug code (although it adds two new ones.)