Iterator

        pub const Iterator = struct {
            next_idx: u32,
            prong_infos: []const Inst.SwitchBlock.ProngInfo,
            multi_case_items_lens: []const u32,
            multi_case_ranges_lens: ?[]const u32,
            item_infos: []const Inst.SwitchBlock.ItemInfo,

            pub fn next(it: *Iterator) ?Case {
                const idx = it.next_idx;
                if (idx == it.prong_infos.len) return null;
                it.next_idx += 1;
                const scalar_cases_len = it.prong_infos.len - it.multi_case_items_lens.len;
                return if (idx < scalar_cases_len) .{
                    .index = .{
                        .kind = .scalar,
                        .value = @intCast(idx),
                    },
                    .prong_info = it.prong_infos[idx],
                    .item_infos = it.itemInfos(1),
                    .range_infos = &.{},
                } else .{
                    .index = .{
                        .kind = .multi,
                        .value = @intCast(idx - scalar_cases_len),
                    },
                    .prong_info = it.prong_infos[idx],
                    .item_infos = it.itemInfos(it.multi_case_items_lens[idx - scalar_cases_len]),
                    .range_infos = if (it.multi_case_ranges_lens) |ranges_lens| b: {
                        break :b @ptrCast(it.itemInfos(2 * ranges_lens[idx - scalar_cases_len]));
                    } else &.{},
                };
            }
            fn itemInfos(it: *Iterator, count: u32) []const Inst.SwitchBlock.ItemInfo {
                const lens = it.item_infos[0..count];
                it.item_infos = it.item_infos[count..];
                return lens;
            }
        }