m.getOrPut(k) { mutableMapOf<String, Any>() } as? MutableMap<String, Any> ?: throw TotallyNotAClassCastExceptionException("This is fine")

mutableMapOf

Any

Any

val list = listOf("a = 1", "a.b = 2")

listOf("a = 1", "a.b = 2")

listOf("a.b = 1", "a = 2")

fun <T> foo(param: T) where T: Iface1, T: Iface2

tailrec

tailrec fun loop(list: List<String>, acc: Pair<String, Any>): Map<String, Any> =
        when {
            list.isEmpty() -> mapOf(acc)
            else -> {
                val tail = list.drop(1)
                loop(tail,
                        if (tail.isEmpty()) acc
                        else Pair(tail[0], mapOf(acc)))
            }
        }

fun main(args: Array<String>): Unit {
    val s = "a.b.c.d = 20" //hacky cleanup, should be done with proper parsers
    val exp = s.replace(" ", "").split("=")
    val lhs = exp[0].split(".").reversed()
    val rhs = exp[1]
    val result = loop(lhs, Pair(lhs[0], rhs))
    println(result) // {a={b={c={d=20}}}}
}

T::class

KClass<out T>