Can we write a generic Array.sum method?

public interface AO[T] {

    public operator + this: T;
    public operator - this: T;

    public operator this + (that: T): T;
    public operator this - (that: T): T;
    public operator this * (that: T): T;
    public operator this / (that: T): T;
    public operator this % (that: T): T;
}

class A[T] implements (Int)=>T {

    val t:T;

    public def apply(int):T = t;

    def sum() {T <: AO[T]} {
        var s:T = 0 as T; // generic additive identity
        s += this(0); // generic addition
        return s;
    }

    def this(t:T) {
        this.t = t;
    }
}

public class Bug {
    public static def main(args:Rail[String]) {
        val a = new A[Int](1);
        System.out.println("a.sum() " + a.sum());
    }
}