Macro regex_if

regex_if!() { /* proc-macro */ }

Return an Option, with T being the type returned by the block or expression given as third argument.

If the regex matches, executes the expression and return it as Some. Return None if the regex doesn’t match.

 let grey = regex_if!(r#"^gr(a|e)y\((?<level>\d{1,2})\)$"#, "grey(22)", {
     level.parse().unwrap()
 });
 assert_eq!(grey, Some(22));