```fun <K, V> MutableMap<Set<K>, V&...

# announcements

[LS]

fun <K, V> MutableMap<Set<K>, V>.put2(vararg keys: K, value: V) = put(keys.toSet(), value)

fun main() {
    val map = mutableMapOf<Set<Int>, String>()
    map.put2(1, 2, 3, value = "x") // no errors
    map.put2(1, 2, 3, "x") // compiler error: No value passed for parameter 'value'
}

wouldn't it make sense for the compiler to figure the last argument on its own in this scenario?

[Casey Brooks]

putting values after varargs is confusing to read, there’s nothing at the call-site to suggest the first 3 parameters are varargs. Maybe try moving the value into a lambda parameter?

inline fun <K, V> MutableMap<Set<K>, V>.put2(vararg keys: K, value: ()->V) = put(keys.toSet(), value())
fun main() {
    val map = mutableMapOf<Set<Int>, String>()
    map.put2(1, 2, 3) { "x" }
}

[StavFX]

If you change the type of map to Map<Set<Any>, String>> do you still expect “x” to be value? Or should it be part of keys then?

[LS]

I guess it might end up being confusing in some cases..
@StavFX In case of ambiguity I'd expect a compiler error

[StavFX]

I’m biased because in Java varargs have to be the last parameters in a method signature, so it doesn’t even make sense to me to put it as the first.
But I think the only reason it’s allowed in Kotlin is because you of name parameters.
I guess I see your point, the compiler COULD be smart enough to infer it in some cases, but like @Casey Brooks said, I think it’s confusing to write that code even if it worked.