pub trait Foo<'a> {
    type Bar: std::fmt::Debug;
    fn baz(&'a self) -> Self::Bar;
}

pub struct X {
    name : String,
}

impl<'a> Foo<'a> for X {
    type Bar = &'a String;
    fn baz(&'a self) -> &'a String {
        &self.name
    }
}

pub fn foo<T: for<'a> Foo<'a>>(x: T) {
    let y = x.baz();
    drop(x);
    // for T = X, this is a &String pointing to dropped memory
    println!("{:?}", y); 
}

pub fn main() {
    foo(X { name: "foo".to_string() });
}