macro_rules! cancel { () => { ... }; ($arg:expr) => { ... }; ($($arg:tt)*) => { ... }; }
Cancel message.
Write a message when cancelled.
Can take either a fmt string like format!, a type that implements Display, or nothing.
format!
Display
use may_clack::cancel; // empty cancel!(); // fmt string cancel!("fmt {:?}", "string"); // impl Display cancel!("text"); cancel!(4);