interface A { val field: Int }
data class B(override val field: Int): A

fun <T: A> myFunction(property: KProperty1<T, Int>? = null) {
    val kProperty = (property ?: A::field) as KProperty1<Any, Int>
    /* Something */
}

fun main() {
    myFunction(B::field)
}

Solved it with a small hack 👌

I tried with

<out T, Int>

. But that breaks the usage of

kProperty.get

as now it requires a

Nothing

object instead of

T

or

A

.