container.kt

class A {
    fun hello() = "hello"
}

class Container {
    val container: MutableMap<String, Any> = mutableMapOf()
    
    fun add(label: String, item: Any) {
        container.put(label, item)
    }
  
    inline fun <reified T> get(item: String): T {
        val res = container[item]
        return if (res is T) res 
            else throw RuntimeException("Item type and name did not match any records.")
    }
}

fun main() {
    val container = Container()
    
    container.add("a", A())
    val a = container.get<A>("a")
    
    println(a.hello())
}