use std::fmt;

trait Show: fmt::Display + fmt::Debug {}

impl<T> Show for T where T: fmt::Display + fmt::Debug {}

fn debug<T: fmt::Debug>(x: &[T]) {

}

fn main() {
    let x: Box<String> = Box::new(String::from("hello, world"));
    let x: Box<usize> = Box::new(42);
    let mut y: Vec<Box<dyn Show>> = Vec::new();
    y.push(x);
    debug(y.as_slice())
}