Macro ward::guard

macro_rules! guard {
    (let $result:ident = $o:expr) => { ... };
    (let $result:ident = $o:expr, else $body:block) => { ... };
    (let mut $result:ident = $o:expr) => { ... };
    (let mut $result:ident = $o:expr, else $body:block) => { ... };
}

Creates a variable with the contents of a Option<T>'s Some(T), otherwise it returns early from the function.

Examples

// res is set to sut's contents
let sut = Some("test");
guard!(let res = sut);
assert_eq!("test", res);

// Because sut is None, the guard! returns early
let sut = None;
guard!(let mut res = sut);
unreachable!();

// Because sut is None, the guard!'s else branch will be run before it returns early
let sut = None;
guard!(let _res = sut, else {
    println!("This code will run!");
});
unreachable!();