NNBD - Why is the static analyzer unable to check final class fields?

Question

I'm confused why the compiler is unable to pass this without complaining:

Even if we ignore the fact that the field usage is directly following the null-check (which the compiler should be able to check?), the field is final, it can not be changed in any case. What's the problem here?

This also gives an error:

class Foo extends StatelessWidget {
  const Foo({Key? key, required this.value}) : super(key: key);
  final String? value;

  @override
  Widget build(BuildContext context) {
    if(value == null) return Container();
    return Text(value); // Error here, thinks this could still be null
  }
}