I would like to write something like this: ```fun test(foo: List<Number>) { if (foo.contains...

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[Tianyu Zhu]

I would like to write something like this:

fun test(foo: List<Number>) {
  if (foo.containsOnly<Int>()) {
    val bar: List<Int> = foo
  }
}

Note that I don't want to use filterIsInstance() here.

Is it possible to write an extension function that allows for this smart-cast?

[MR3Y]

have you tried?:

inline fun <reified T: Number> List<Number>.containsOnly(): Boolean {
    contract {
        returns(true) implies this is List<T>
    }
    forEach {
        if(it !is T) return false
    }
    return true
}

[Tianyu Zhu]

I tried that but the compiler complains about this is List<T> because List<T> contains an erased type