(invalid) Add "\{", "\}" literal escaping for format strings (use "{{", "}}")

[0joshuaolson1]

They can't be printed without interpolating:

const print = @import("std").debug.warn;
pub fn main() void {
 print("}}{ }{}{0}\n", "1"); // error, instead print("{}{}{}\n", "}}{ }", "1", "{0}");
}

EDIT: Numbers don't work, so have a "1".

[andrewrk]

const std = @import("std");

pub fn main() void {
    std.debug.warn("{{ }}\n");
    std.debug.warn("{{0}}\n");
}

> ./test
{ }
{0}

Working as expected for me.

const std = @import("std");

pub fn main() void {
    std.debug.warn("}}}}{{ }}{}{{0}}\n", "1");
}

> ./test
}}{ }1{0}

[andrewrk]

Related: #965