fn main() {
    // Note: explicit type annot is required here
    // because otherwise the inference gets smart
    // and assigns a type of ~[mut ~[const int]].
    let v: ~[mut ~[mut ~[int]]] = ~[mut ~[mut ~[0]]];

    fn f(&&v: ~[mut ~[mut ~[const int]]]) {
        v[0][1] = ~[mut 3]
    }

    f(v); //~ ERROR (values differ in mutability)
}