use supply::prelude::*;

struct Demo<'s> {
    s: &'s str,
}

impl<'r, 's> Provider<'r> for Demo<'s> {
    type Lifetimes = l!['s];

    fn provide(&'r self, want: &mut dyn Want<Self::Lifetimes>) {
        // The AddLt is to make it &'s str.
        want.provide_tag::<&str>(self.s);
    }
}

#[test]
fn example() {
    // A string that lives longer than demo.
    let s = String::from("hello");

    let s_ref = {
        let demo = Demo { s: &s };

        // The AddLt here bumps the lifetime of the &str to
        // be &'s str instead of &'r str. That way we can return
        // the borrow from this scope.
        demo.request::<&str>()
    };

    // This is a reference to s as expected.
    assert_eq!(s_ref, Some("hello"));
}