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