abstract class IdeaBugTest<M extends IdeaBugTest.Mapping>
{
        static class Mapping {}
}

class BugTestSub extends IdeaBugTest<<error descr="SubMapping is not accessible in current context">BugTestSub.SubMapping</error>>
{
        public abstract static class SubMapping extends Mapping {}
}

class BugTestSub1 extends IdeaBugTest<BugTestSub1.SubMapping>
{
        public abstract static class SubMapping extends IdeaBugTest.Mapping {} //fqn here
}

class AbstractSettings {
    interface State {}
}
interface SomeInterface<T> {}
class Settings extends AbstractSettings implements SomeInterface<Settings.MyState> {
    static class MyState implements State {}
}