Rust ベクタ（可変配列）の値の総和を求める

ベクタ.iter().sum::<isize>();

fn main() {

    let v = vec![ 1, 2, 3, 4, 5 ];

    println!("{:?}", v.iter().sum::<isize>()); // 15

}

fn main() {

    let v = vec![0; 0];

    println!("{:?}", v.iter().sum::<isize>()); // 0

}

fn main() {

    let v = vec![ '1', '2', '3' ];

    println!("{:?}", v.iter().sum::<isize>()); 
　　// error[E0277]: the trait bound `isize: Sum<&char>` is not satisfied

}