js.compile.ignore=true
=====
>>> main.whiley
public export method test():
   int[] xs = [1,2,3]
   int[] ys = xs[1:=4][2:=5]
   // check xs unchanged
   assert xs[0] == 1 
   assert xs[1] == 2
   assert xs[2] == 3
   // check ys changed
   assert ys[0] == 1
   assert ys[1] == 4
   assert ys[2] == 5
   // Final check
   assert ys == [1,4,5]
---