import kotlin.reflect.KClass

fun main(args: Array<String>) {
    val x = Test<String>()
    x.prop = "instance for string"
    println(Test<String>().prop)
}

class Test<F: Any> private constructor() {
    lateinit var prop: F

    companion object {
    	private val instances = hashMapOf<KClass<*>, Test<*>>()

        inline operator fun <reified S: Any> invoke(): Test<S> = getInstance<S>(S::class)

        fun <T: Any> getInstance(type: KClass<*>): Test<T> = instances[type] as? Test<T> ?: run {
            val result = Test<T>()
            instances.put(type, result)
            result
        }
    }
}