From references-change-permissions-on-places, places have three kinds of permission on their data:

• Read (R): data can be copied to another location.

• Write (W): data can be mutated.

• Own (O): data can be moved or dropped.

In the example

fn main() {
    let mut v: Vec = vec![1, 2, 3];
    let num: &i32 = &v[2];
    println!("Third element is {}", *num);
    v.push(4);
}

From the third line, reference num gain permissions R and O but no W since it was not marked as let mut .

What can we do if a reference have permissions R and O?

I know that reference do not own its data, so how to read its data? Also, how to move a reference?