A DESCRIPTION OF THE PROBLEM :
JDK8 javac compiles a public class (PodcastListFragment) with a generic parameter (PodcastIdentifiedListStateType) extending a one of its own public inner interfaces (PodcastIdentifiedListState) that extends a protected inner interface (State) of the class' superclass (RxListAsyncValueFragment):

public abstract class PodcastListFragment<
        PodcastListFragmentType extends PodcastListFragment<
                        PodcastListFragmentType,
                        PodcastListFragmentListenerType,
                        PodcastListAttachmentType,
                        PodcastIdentifiedListStateType,
                        PodcastIdentifiedListAsyncStateType,
                        LoadingType,
                        CompleteType,
                        FailedType
                        >,
        PodcastListFragmentListenerType extends PodcastListFragmentListener<
                        PodcastListFragmentType,
                        PodcastListFragmentListenerType,
                        PodcastListAttachmentType,
                        PodcastIdentifiedListStateType,
                        PodcastIdentifiedListAsyncStateType,
                        LoadingType,
                        CompleteType,
                        FailedType
                        >,
        PodcastListAttachmentType extends RxFragment.Attachment<
                PodcastListFragmentType,
                PodcastListFragmentListenerType,
                PodcastListAttachmentType
                >,
        PodcastIdentifiedListStateType extends PodcastListFragment.PodcastIdentifiedListState<
                PodcastIdentifiedListAsyncStateType,
                LoadingType,
                CompleteType,
                FailedType
                >,
        PodcastIdentifiedListAsyncStateType extends PodcastListFragment.PodcastIdentifiedListAsyncState<
                LoadingType,
                CompleteType,
                FailedType
                >,
        LoadingType extends PodcastListFragment.PodcastIdentifiedListAsyncState.PodcastIdentifiedListAsyncStateLoading<
                LoadingType,
                CompleteType,
                FailedType
                >,
        CompleteType extends PodcastListFragment.PodcastIdentifiedListAsyncState.PodcastIdentifiedListAsyncStateComplete<
                LoadingType,
                CompleteType,
                FailedType
                >,
        FailedType extends PodcastListFragment.PodcastIdentifiedListAsyncState.PodcastIdentifiedListAsyncStateFailed<
                LoadingType,
                CompleteType,
                FailedType
                >
        > extends RxListAsyncValueFragment<
        PodcastListFragmentType,
        PodcastListFragmentListenerType,
        PodcastListAttachmentType
        > { ... }

public abstract class RxListAsyncValueFragment<
        FragmentType extends RxListAsyncValueFragment<
                FragmentType,
                ListenerType,
                AttachmentType
                >,
        ListenerType,
        AttachmentType extends RxFragment.Attachment<
                FragmentType,
                ListenerType,
                AttachmentType
                >
        > extends RxAsyncValueFragment<
        FragmentType,
        ListenerType,
        AttachmentType
        > { ... }

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Build https://github.com/hborders/HeathCast/tree/jdk_8_bug with gradle and JAVA_HOME=JDK8:
./gradlew assembleDebug

Everything builds fine.

Now build with JAVA_HOME=JDK9

> Task :app:compileDebugJavaWithJavac FAILED
/Users/hborders/workspace/HeathCast/app/src/main/java/com/github/hborders/heathcast/fragments/PodcastListFragment.java:43: error: type argument PodcastListFragmentType is not within bounds of type-variable FragmentType
                PodcastListFragmentType,
                ^
  where PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType,FragmentType,ListenerType,AttachmentType are type-variables:
    PodcastListFragmentType extends PodcastListFragment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListFragmentListenerType extends PodcastListFragmentListener<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListAttachmentType extends Attachment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType> declared in class PodcastListFragment
    PodcastIdentifiedListStateType extends PodcastIdentifiedListState<PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastIdentifiedListAsyncStateType extends PodcastIdentifiedListAsyncState<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    LoadingType extends PodcastIdentifiedListAsyncStateLoading<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    CompleteType extends PodcastIdentifiedListAsyncStateComplete<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FailedType extends PodcastIdentifiedListAsyncStateFailed<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FragmentType extends RxFragment<FragmentType,ListenerType,AttachmentType> declared in class Attachment
    ListenerType extends Object declared in class Attachment
    AttachmentType extends Attachment<FragmentType,ListenerType,AttachmentType> declared in class Attachment
/Users/hborders/workspace/HeathCast/app/src/main/java/com/github/hborders/heathcast/fragments/PodcastListFragment.java:427: error: type argument PodcastListFragmentType is not within bounds of type-variable FragmentType
                    PodcastListFragmentType,
                    ^
  where PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType,FragmentType,ListenerType,AttachmentType are type-variables:
    PodcastListFragmentType extends PodcastListFragment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListFragmentListenerType extends PodcastListFragmentListener<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListAttachmentType extends Attachment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType> declared in class PodcastListFragment
    PodcastIdentifiedListStateType extends PodcastIdentifiedListState<PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastIdentifiedListAsyncStateType extends PodcastIdentifiedListAsyncState<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    LoadingType extends PodcastIdentifiedListAsyncStateLoading<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    CompleteType extends PodcastIdentifiedListAsyncStateComplete<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FailedType extends PodcastIdentifiedListAsyncStateFailed<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FragmentType extends RxFragment<FragmentType,ListenerType,AttachmentType> declared in interface AttachmentFactory
    ListenerType extends Object declared in interface AttachmentFactory
    AttachmentType extends Attachment<FragmentType,ListenerType,AttachmentType> declared in interface AttachmentFactory
/Users/hborders/workspace/HeathCast/app/src/main/java/com/github/hborders/heathcast/fragments/PodcastListFragment.java:432: error: type argument PodcastListFragmentType is not within bounds of type-variable FragmentType
                    PodcastListFragmentType,
                    ^
  where PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType,FragmentType,ListenerType,AttachmentType are type-variables:
    PodcastListFragmentType extends PodcastListFragment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListFragmentListenerType extends PodcastListFragmentListener<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListAttachmentType extends Attachment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType> declared in class PodcastListFragment
    PodcastIdentifiedListStateType extends PodcastIdentifiedListState<PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastIdentifiedListAsyncStateType extends PodcastIdentifiedListAsyncState<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    LoadingType extends PodcastIdentifiedListAsyncStateLoading<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    CompleteType extends PodcastIdentifiedListAsyncStateComplete<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FailedType extends PodcastIdentifiedListAsyncStateFailed<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FragmentType extends RxFragment<FragmentType,ListenerType,AttachmentType> declared in interface OnAttached
    ListenerType extends Object declared in interface OnAttached
    AttachmentType extends Attachment<FragmentType,ListenerType,AttachmentType> declared in interface OnAttached
/Users/hborders/workspace/HeathCast/app/src/main/java/com/github/hborders/heathcast/fragments/PodcastListFragment.java:437: error: type argument PodcastListFragmentType is not within bounds of type-variable FragmentType
                    PodcastListFragmentType,
                    ^
  where PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType,FragmentType,ListenerType,AttachmentType are type-variables:
    PodcastListFragmentType extends PodcastListFragment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListFragmentListenerType extends PodcastListFragmentListener<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListAttachmentType extends Attachment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType> declared in class PodcastListFragment
    PodcastIdentifiedListStateType extends PodcastIdentifiedListState<PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastIdentifiedListAsyncStateType extends PodcastIdentifiedListAsyncState<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    LoadingType extends PodcastIdentifiedListAsyncStateLoading<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    CompleteType extends PodcastIdentifiedListAsyncStateComplete<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FailedType extends PodcastIdentifiedListAsyncStateFailed<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FragmentType extends RxFragment<FragmentType,ListenerType,AttachmentType> declared in interface WillDetach
    ListenerType extends Object declared in interface WillDetach
    AttachmentType extends Attachment<FragmentType,ListenerType,AttachmentType> declared in interface WillDetach
/Users/hborders/workspace/HeathCast/app/src/main/java/com/github/hborders/heathcast/fragments/PodcastListFragment.java:442: error: type argument PodcastListFragmentType is not within bounds of type-variable FragmentType
                    PodcastListFragmentType,
                    ^
  where PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType,FragmentType,ListenerType,AttachmentType are type-variables:
    PodcastListFragmentType extends PodcastListFragment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListFragmentListenerType extends PodcastListFragmentListener<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType,PodcastIdentifiedListStateType,PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastListAttachmentType extends Attachment<PodcastListFragmentType,PodcastListFragmentListenerType,PodcastListAttachmentType> declared in class PodcastListFragment
    PodcastIdentifiedListStateType extends PodcastIdentifiedListState<PodcastIdentifiedListAsyncStateType,LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    PodcastIdentifiedListAsyncStateType extends PodcastIdentifiedListAsyncState<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    LoadingType extends PodcastIdentifiedListAsyncStateLoading<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    CompleteType extends PodcastIdentifiedListAsyncStateComplete<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FailedType extends PodcastIdentifiedListAsyncStateFailed<LoadingType,CompleteType,FailedType> declared in class PodcastListFragment
    FragmentType extends RxFragment<FragmentType,ListenerType,AttachmentType> declared in interface StateObservableProvider
    ListenerType extends Object declared in interface StateObservableProvider
    AttachmentType extends Attachment<FragmentType,ListenerType,AttachmentType> declared in interface StateObservableProvider
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
5 errors

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
JDK 8 should emit the same error as JDK 9.
ACTUAL -
JDK 8 emits no error, and things run normally.

---------- BEGIN SOURCE ----------
https://github.com/hborders/HeathCast/tree/jdk_8_bug
---------- END SOURCE ----------

FREQUENCY : always