the spec for sealed types [1] states:

It is a compile-time error if an annotation type declaration has the modifier sealed. The compiler is currently accepting this code:

public sealed @interface MyAnno {}

non-sealed interface Foo extends MyAnno {}

the compiler should be in sync with the spec.

[1] http://cr.openjdk.java.net/~gbierman/jep360/jep360-20200526/specs/sealed-classes-jls.html#jls-9.6

reported by Tagir at:
https://mail.openjdk.java.net/pipermail/amber-dev/2020-August/006447.html