Nullness Checker unsoundness with inner classes

import org.checkerframework.checker.nullness.qual.Nullable;
public class Test {
    class A<X> {
        X field;
        A(X val) {this.field = val;}
        class B<Y> {
            X get() { return A.this.field; }
        }
    }
    void test(A<@Nullable String>.B<@Nullable String> b) {
        b.get().hashCode();
    }
    public static void main(String[] args) {
      Test t = new Test();
      t.test(t.new A<@Nullable String>(null).new B<@Nullable String>());
    }
}

This passes the Nullness Checker but throws an NPE at runtime. I think there should be an error reported inside test() at the de-reference of b.get().

Start by running the supplied Java reproducer with the Nullness Checker and confirm that the dereference of b.get() is accepted before the runtime NPE. Trace the Nullness Checker handling of generic inner classes and qualified outer-instance fields; done means the checker reports an error at that dereference and the regression is covered by a test.