"Extension types" for Kotlin

Language Design
46

It seems to me that as long as you are fine with EXPLICIT vs. implicit then you can basically do it now like this:

val String.monoid get() = object : Monoid<String> {
    override fun zero() = ""
    override fun append( a1: String, a2: String) = a1 + a2
}

Then you can just do MyString.monoid to explicitly convert to a monoid.

If you want implicit conversion aren’t you then moving to morass of implicit conversion that lead IntelliJ to reject Scala and create Kotlin to begin with?