#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::fmt;
struct Foo(Vec<(String, i32)>);
impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
    }
}
fn main() {
    assert_eq!(
        format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
        r#"{"A": 10, "B": 11}"#
    );
}