use std::str;

fn main() {
    {
        let b = vec![240, 159, 146, 150];
        let x = unsafe { str::from_utf8_unchecked(&b) };
        assert_eq!("💖", x);
    }

    {
        let b = vec![240, 159, 146];
        let x = unsafe { str::from_utf8_unchecked(&b) };
        println!("{}", x);
    }
}