Kotlin duck typing / type classing fiddle

KotlinDuckTyping.kt

import java.lang.reflect.*
import java.util.*

class A {
    fun shout() = println("go team A!")
}

class B {
    fun shout() = println("go team B!")
}

interface Shoutable {
    fun shout()
}

class InvokeHandler(private val underlying: Any) : InvocationHandler {
    override fun invoke(proxy: Any, method: Method, args: Array<out Any?>?): Any? {
        for (fn in underlying.javaClass.methods) {
            if (fn.name == method.name && Arrays.equals(fn.parameterTypes, method.parameterTypes)) {
                if (args == null)
                    return fn.invoke(underlying)
                else
                    return fn.invoke(underlying, *args)
            }
        }
        throw UnsupportedOperationException("$method with $args")
    }
}

inline fun <reified T> Any.dynamicCast(): T {
    return Proxy.newProxyInstance(javaClass.classLoader, arrayOf(T::class.java), InvokeHandler(this)) as T
}

fun main(args: Array<String>) {
    val a = A()
    val b = B()

    val sa = a.dynamicCast<Shoutable>()
    val sb = b.dynamicCast<Shoutable>()

    sa.shout()
    sb.shout()
}