ward

This crate exports two macros, which are intended to replicate the functionality of Swift's guard expression with Option<T> usage. They both do similar things, but the ward! macro technically has more use cases than the guard! macro, because it returns a value instead of creating a variable.

Examples

let sut = Some("test");

// This creates the variable res, which from an Option<T> will return a T if it is Some(T), and will
// otherwise return early from the function.
guard!(let res = sut);
assert_eq!("test", res);

The ward! macro, by comparison, just returns the value, without forcing you to make a variable from it (although we still do in this example):

let sut = Some("test");
let res = ward!(sut);
assert_eq!("test", res);

Both macros also support an else branch, which will run before the method returns early:

let sut = None;
guard!(let _res = sut, else {
    println!("This will be called!");
});
unreachable!();

Both macros also support an alternative "early return statement", which will let you e.g. break in loops:

// Not that you couldn't (and probably should) do this case with `while let Some(res) = sut`...
let mut sut = Some(0);
loop {
    let res = ward!(sut, break);
    sut = if res < 5 {
        Some(res + 1)
    } else {
        None
    }
}
assert_eq!(sut, None);