Macro wif

macro_rules! wif {
    ($cond:expr => $true:block $(else $false:block)?) => { ... };
}

if but use weak_true result value

Examples

let r = wif!("" => {
    1
} else {
    0
});
assert_eq!(r, 0);

wif!("" => {
    unreachable!()
});
wif!('\0' => { } else {
    unreachable!()
});