Walk through the code. Confirm that the audience is familiar with the dereference operator.

Attempt to compile the code, trigger the compiler error.

Add the unsafe block:

fn main() {
    let numbers = vec![0, 1, 2, 3, 4];
    let i = numbers.len() / 2;

 let x = unsafe { *numbers.get_unchecked(i) };
    assert_eq!(i, x);
}

Prompt audience for a code review. Guide learners towards adding a safety comment.

Add the safety comment:

#![allow(unused)]
fn main() {
// SAFETY: `i` must be within 0..numbers.len()
}

Suggested Solution

fn main() {
    let numbers = vec![0, 1, 2, 3, 4];
    let i = numbers.len() / 2;

    let x = unsafe { *numbers.get_unchecked(i) };
    assert_eq!(i, x);
}