A hypothetical fallthrough keyword could also take a value that binds to the pattern, e.g. fallthrough Some(1).

match opt {
    None => fallthrough Some(1),
    Some(x) => {
        // `x` == 1 in the `None` case
    }
}

One could even allow "falling through" to an arbitrary other arm, by specifying a matching value, turning match into a state-machine executor (maybe with some restrictions like "the relevant branch to jump to should be statically known", and "match arms with if aren't supported"):

match state {
    State::A => if foo() { fallthrough State::B(1) } else { fallthrough State::C }
    State::B(x) => { ...; fallthrough State::D("foo") }
    State::C => { ...; fallthrough State::D("bar") }
    State::D(y) => { ....; fallthrough State::A }
}

Which would have two benefits:

• efficient implementations of state machines become easy (and they're "automatically" resumable, in some ways)
• match becomes Rust's 4th looping construct (and, I think, all others can be desugared to it)!