#![allow(unused_variables)]
#![feature(string_from_utf8_lossy_owned)]
fn main() {
    let input: Vec<u8> = b"Hello \xF0\x90\x80World".into();
    let output = String::from_utf8(input).unwrap_or_else(|e| e.into_utf8_lossy());
    assert_eq!(String::from("Hello �World"), output);
}