const Point = struct {
    x: u32,
    y: u32,
    label: []const u8,
};

const p = Point{ .x = 0, .y = 1, .label = "A" };
// merge to new struct
const new_p = merge(p, .{ .x = 2, .label = "B" });
// pass multi struct is ok
const new_p_2 = merge(p, .{ .{ .x = 2 }, .{ .label = "B" } });

const Point = struct {
    x: u32,
    y: u32,
    label: []const u8,
};

var p = Point{ .x = 0, .y = 1, .label = "A" };
// update struct in-place
update(&p, .{ .x = 2, .label = "B" });
// pass multi struct is ok
update(&p, .{ .{ .x = 2 }, .{ .label = "B" } });