why doesn't the following code crash: ``` fun mai...

# announcements

[kirillrakhman]

why doesn't the following code crash:

fun main(args: Array<String>) {
    println(Foo().bar("hello ", "world"))
}

interface IFoo {
    open fun bar(a: String, b: String ) = a + b
}

class Foo : IFoo {
    override fun bar(a: String, b: String) = super.bar(a, b)
}