#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::fmt;
use std::marker::PhantomData;
struct Foo<T>(i32, String, PhantomData<T>);
impl<T> fmt::Debug for Foo<T> {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_tuple("Foo")
            .field(&self.0)
            .field(&self.1)
            .field(&format_args!("_"))
            .finish()
    }
}
fn main() {
    assert_eq!(
        "Foo(10, \"Hello\", _)", format!("{:?}", Foo(10, "Hello".to_string(),
        PhantomData::< u8 >))
    );
}