A frontmatter chapter.

// Lifetimes are annotated below with lines denoting the creation
// and destruction of each variable.
// `i` has the longest lifetime because its scope entirely encloses 
// both `borrow1` and `borrow2`. The duration of `borrow1` compared 
// to `borrow2` is irrelevant since they are disjoint.
fn main() {
    let i = 3; // Lifetime for `i` starts. ────────────────┐
    //                                                     │
    { //                                                   │
        let borrow1 = &i; // `borrow1` lifetime starts. ──┐│
        //                                                ││
        println!("borrow1: {}", borrow1); //              ││
    } // `borrow1 ends. ──────────────────────────────────┘│
    //                                                     │
    //                                                     │
    { //                                                   │
        let borrow2 = &i; // `borrow2` lifetime starts. ──┐│
        //                                                ││
        println!("borrow2: {}", borrow2); //              ││
    } // `borrow2` ends. ─────────────────────────────────┘│
    //                                                     │
}   // Lifetime ends. ─────────────────────────────────────┘