Why are Arrays invariant, but Lists covariant?

Question

E.g. why does

val list:List[Any] = List[Int](1,2,3) 

work, but

val arr:Array[Any] = Array[Int](1,2,3) 

fails (because arrays are invariant). What is the desired effect behind this design decision?

Answer 1

Because it would break type-safety otherwise. If not, you would be able to do something like this:

val arr:Array[Int] = Array[Int](1,2,3) val arr2:Array[Any] = arr arr2(0) = 2.54 

and the compiler can't catch it.

On the other hand, lists are immutable, so you can't add something that is not Int