What does this Zig snippet output?

1const std = @import("std");
2const Op = union(enum) {
3    add: i32,
4    mul: i32,
5    nop,
6};
7pub fn main() void {
8    const op = Op{ .add = 5 };
9    switch (op) {
10        .add => |v| std.debug.print("add {d}\n", .{v}),
11        .mul => |v| std.debug.print("mul {d}\n", .{v}),
12        .nop => std.debug.print("nop\n", .{}),
13    }
14}