Code shared from the Rust Playground

playground.rs

fn foo<T : std::convert::Into<usize>>(d : &T) -> usize {
	d.into()
}

struct Bar {
    a : usize
}

impl std::convert::Into<usize> for Bar {
    fn into(self) -> usize {
        self.a
    }
}

fn main() {
    let bar = Bar { a : 15 };
    
    assert!(foo(&bar) == 15);
}