2026-08-21
borrow.rs
fn push_and_print(v: &mut Vec<i32>) {
let first = &v[0];
v.push(42);
println!("{}", first);
}
This doesn't compile. Fix it while keeping the printed value the original first element.
Answer
first borrows v immutably, but v.push needs a mutable borrow, and first is still alive at the println!. Since i32 is Copy, take the value instead of a reference: let first = v[0]; — then push and print freely.