Reproducing issue

Open sk/redeemer/eclipse/jdt/sealing/SubSubInterfaceA.java file in Eclipse IDE, you will see 2 errors reported:

• on 'SubSubInterfaceA': The hierarchy of the type SubSubInterfaceA is inconsistent
• on 'TestClassB': Permitted type TestClassB does not declare sk.redeemer.eclipse.jdt.sealing.SubSubInterfaceA as direct super interface

(also reported in vertical / overview ruler)

Neither Errors nor Markers view display these errors.

Source code is obviously compiled properly since it's possible to run Main class in the same package. Also switch expression in Main class is properly considered exhaustive, thus it seems compiler properly understands sealed classes hierarchy.

Surprisingly working

Single file

Surprisingly no errors are reported for same class hierarchy if declared in single file, see sk.redeemer.eclipse.jdt.sealing.working.onefile.Main.

Same level

Also when a class (TestClassB) implements sealed interfaces on same 'level' within class hierarchy, no errors are reported. See sk.redeemer.eclipse.jdt.sealing.working.samelevel package.