ref: 847f11bb87ebfa7e4de48c05d65c83758d9220e1
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++
;;
}