Type Alias FlatIterable<Itr, Depth>
FlatIterable: { done: Itr; recur: Itr extends Iterable<infer InnerItr> ? FlatIterable< InnerItr, [ -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, ][Depth], > : Itr;}[Depth extends -1 ? "done" : "recur"]