Why are Arrays invariant, but Lists covariant?
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?
Solution 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
Solution 2:
This is because lists are immutable and arrays are mutable.