use std::sync::Arc;

fn main() {
    let mut v: Vec<Arc<dyn Human>> = Vec::new();
    let me = Taiwanese::new();
    // works with a temporarary variable.
    let me_2 = Arc::clone(&me);
    v.push(me_2);
    v.push(Arc::clone(&me)); // type mismatch without temporary variable, why?
    v.push(me);
}

trait Human {}

struct Taiwanese {}

impl Taiwanese {
    fn new() -> Arc<Taiwanese> {
        Arc::new(Taiwanese {})
    }
}

impl Human for Taiwanese {}