With
fun f(b: kotlin.Byte) {
val x = b.describeConstable()
}
and -language-version 1.9 we get
test.kt:2:15: warning: 'describeConstable(): Optional<DynamicConstantDesc<Byte!>!>!' is deprecated. This member is not fully supported by Kotlin compiler, so it may be absent or have different signature in next major version
and with 2.0
test.kt:2:15: error: unresolved reference 'describeConstable'.