The modifier sealed
means that the descendants of a entity may be inherited only if they're declared in the same file as that of the entity. However, in your case, the marked entity does not have any descendants. In such cases, having the sealed
modifier maybe confusing. Either you forgot to declare the entity's descendants, or, the modifier sealed
is not ideal for your use case.
sealed trait ProgrammingLanguage
// Alternative 1: declare descendants
sealed ProgrammingLanguage
case object Scala extends ProgrammingLanguage
// Alternative 2: drop the `sealed` modifier
trait ProgrammingLanguage