JShell does not support sealed types properly, e.g.:
---
jshell> sealed class B permits I {}
|  created class B, however, it cannot be referenced until class I is declared

jshell> final class I extends B {}
|  Warning:
|  Modifier 'final' not permitted in top-level declarations, ignored
|  final class I extends B {}
|  ^---^
|  created class I, however, it cannot be referenced until class B is declared and this error is corrected: 
|      Modifier 'final' not permitted in top-level declarations, ignored
|      final class I extends B {}
|      ^---^

jshell> class I extends B {}
|  modified class I, however, it cannot be referenced until class B is declared
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