Should this work without including <SomeInterfa...

# announcements

[samir]

Should this work without including <SomeInterface> ?

interface SomeInterface
enum class SomeEnum: SomeInterface { ValueA, ValueB }

fun someFun(array: Array<SomeInterface>) {}

fun calls() {
	val val1 = arrayOf<SomeInterface>(SomeEnum.ValueA, SomeEnum.ValueB) // Array<SomeInterface>
	val val2 = arrayOf(SomeEnum.ValueA, SomeEnum.ValueB) // Array<SomeEnum>
	val val3 = SomeEnum.values() // Array<SomeEnum>
	val val4 = SomeEnum.values() as Array<SomeInterface> // Array<SomeInterface>
	
	someFun(arrayOf(SomeEnum.ValueA, SomeEnum.ValueB)) // Works
	someFun(SomeEnum.values()) // Compiler error
	
	someFun(val1) // Works
	someFun(val2) // Compiler error
	someFun(val3) // Compiler error
	someFun(val4) // Works
}

[Shawn]

you might want to use lists instead

[Shawn]

arrays have a .toList() extension method which helps a lot

[samir]

Thanks. I am trying to detect if this is intended behaviour or not for Array.

[Shawn]

I’m pretty sure it is - looking a bit more closely at the code, the declaration for Kotlin arrays is just public class Array<T>, which means T is invariant

[Shawn]

see: http://kotlinlang.org/docs/reference/basic-types.html#arrays

Note: unlike Java, arrays in Kotlin are invariant. This means that Kotlin does not let us assign an Array<String> to an Array<Any>, which prevents a possible runtime failure (but you can use Array<out Any>, see Type Projections).

[Shawn]

it looks like technically you can just redefine someFun() to accept Array<out SomeInterface> but I imagine you do so at your own risk

[samir]

Thanks, I did not know that.