Ownership

All variable bindings have a scope where they are valid and it is an error to use a variable outside its scope:

struct Point(i32, i32);
fn main() {
    {
        let p = Point(3, 4);
        println!("x: {}", p.0);
    }
    println!("y: {}", p.1);
}

We say that the variable owns the value. Every Rust value has precisely one owner at all times.

At the end of the scope, the variable is dropped and the data is freed. A destructor can run here to free up resources.

This slide should take about 5 minutes.

Students familiar with garbage-collection implementations will know that a garbage collector starts with a set of “roots” to find all reachable memory. Rust’s “single owner” principle is a similar idea.