1.11.1. Review
In the beginner tutorial, we mentioned that every reference in Rust has a lifetime. A lifetime is the scope in which the reference remains valid, and in most cases it is implicit and inferred by the compiler.
When you take a reference to a variable, the lifetime begins. When the variable is moved or goes out of scope, the lifetime ends. In other words, for a reference, a lifetime is the name of the code region in which it must remain valid.
Lifetimes usually overlap with scopes, but not always.
1.11.2. Borrow Checker
