zig generic struct methods

fn Node(comptime T: type) type {
    return struct {
        parent: ?*Node(T),
        children: [2]?*Node(T),
        color: Color,
        data: T,
    };
}
fn Iterator(comptime T: type) type {
    const ret = struct {
        node: ?*Node(T),
        pub fn next(self: ret) ?*Node(T) {
            std.debug.print("{}\n", .{self.node});
            if (self.node) |n| {
                if (n.children[1]) |c| {
                    node = c;
                    while (node != null) node = node.?.children[0];
                } else node = node.parent;
                return node;
            } else return null;
        }
    };
    return ret;
}
pub fn main() void {
	var it = Iterator(i32){.node = rb.root};
    while (it.next()) |e| std.debug.print("{} ", .{e});
}