Ох уж эти титеретики
fn main() {
    let a: [i32;5]=[1,2,3,4,5];
    for i in 0..a.len() {
        if i == a.len() - 1 {
            println!("{}", a[i+1]);
        }
    }
}

Compiling playground v0.0.1 (file:///playground)
    Finished release [optimized] target(s) in 0.59 secs
     Running `target/release/playground`
thread 'main' panicked at 'index out of bounds: the len is 5 but the index is 5', /checkout/src/libcore/slice/mod.rs:830:10
note: Run with `RUST_BACKTRACE=1` for a backtrace.