Can't iterate RwLockReadGuard<Vec>

use std::thread;
use std::sync::{RwLock,Arc};
fn main() {
    let primes=Arc::new(RwLock::new(vec![2,3,5]));
    let primes2=primes.clone();
    let primes_w=primes.write().unwrap();
    let handle=thread::spawn(move || {
        let primes_r=primes2.read().unwrap();
        for i in &primes_r {
            println!("{:?}", i);
        }
    });
    primes_w.push(7);
    drop(primes_w);
    handle.join();
}

/*
error[E0277]: the trait bound `&std::sync::RwLockReadGuard<'_, std::vec::Vec<{integer}>>: std::iter::Iterator` is not satisfied
  --> test.rs:9:3
   |
9  |            for i in &primes_r {
   |  ___^ starting here...
10 | |                  println!("{:?}", i);
11 | |          }
   | |___^ ...ending here: the trait `std::iter::Iterator` is not implemented for `&std::sync::RwLockReadGuard<'_, std::vec::Vec<{integer}>>`
   |
   = note: `&std::sync::RwLockReadGuard<'_, std::vec::Vec<{integer}>>` is not an iterator; maybe try calling `.iter()` or a similar method
   = note: required by `std::iter::IntoIterator::into_iter`

error: aborting due to previous error
*/