If I have:

sealed interface Foo

object Bar : Foo

object Baz : Foo

fun <T : Foo> getFooObjects(): List<T> = TODO("How do I get this list?")

the whole T : Foo typing is a bit weird. I get that what you want is only the sealed implementations of Foo, but Foo itself is of type Foo. It sounds like you want it generic? So maybe

inline fun <reified T> getObjectsOfType(): List<T> = T::class.sealedSubclasses.mapNotNull { it.objectInstance }

if not, simply

fun getFooObjects(): List<Foo> = Foo::class.sealedSubclasses.mapNotNull { it.objectInstance }

would do the trick

I ended up with (for setting up the schemas in the db with exposed...) - the problem was that I can't inherit an interface from a class (Table) and SchemaUtils.xxx takes in Tables...:

sealed interface DbTables

object Foos : IntIdTable("foo"), DbTables

val tables = DbTables::class.sealedSubclasses
                        .mapNotNull { kclass -> kclass.objectInstance as? Table }
                        .toTypedArray()

                    SchemaUtils.drop(*tables, inBatch = true)
                    SchemaUtils.create(*tables, inBatch = true)