That's quite an error for such a small piece of code... None of the following functions can be called with the arguments supplied: final fun <T:Any?,R:Any?> Array<T>.map(var result:Collection<R>,var transform:Function1<T,R>):Collection<R> defined<java_root>std final fun <T:Any?,R:Any?>Interable<T>.map(var result:Collection<R>,var transform:Function1<T,R>):Collection<R>defined in <java_root>.std