But Rust doesn't care how many things you want to return?

    fn six_numbers() -> (u8, u8, u8, u8, u8, u8) {
        (10, 20, 30, 40, 50, 60)
    }

    fn in_an_array() -> [u8; 6] {
        [10, 20, 30, 40, 50, 60]
    }

The return type must be sized, because otherwise how can we put that anywhere? But of course your answer can just be to put it on the heap inside a Box...

    fn heap_numbers() -> Box<[u8]> {
        let mut slice = Box::new_uninit_slice(6);
        slice[0].write(10);
        slice[1].write(20);
        slice[2].write(30);
        slice[3].write(40);
        slice[4].write(50);
        slice[5].write(60);
        unsafe { slice.assume_init() }
    }