ref: bc7052e02f9bdbb93b13987d83f8572b4f657687
dir: /lib/iter/test/enum.myr/
use std
use iter
const main = {
var n
n = 0
for (x, i) : iter.byenum([1,3,5,7,9][:])
std.assert(x == n, "invalid enum idx {}", x)
std.assert(i == n*2 + 1, "invalid enum val {}", i)
n++
;;
}