You may be using a Rust version older than 1.53.0, in which IntoIterator for arrays was added. Prior to that version you would get error[E0277]: [{integer}; 5] is not an iterator.
You should consider upgrading your Rust version. If that is not practical, you could read an older version of the book.
If that's not what you see, please show us the complete output your compiler gives you.