Compare tree in Rust

gistfile1.rs

fn is_same_tree(p: &Tree<int>, q: &Tree<int>) -> bool {
    match (*p, *q) { // error: cannot move out of dereference of `&`-pointer
        (None, None) => true,
        (Some(ref a), Some(ref b)) => {
            if a.val == b.val
            && is_same_tree(&a.left, &b.left)
            && is_same_tree(&a.right, &b.right){
                true
            } else {
                false
            }
        },
        (_, _) => false,
    }
}

type Tree<T> = Option<Box<TreeNode<T>>>;

struct TreeNode<T> {
    val: T,
    left: Tree<T>,
    right: Tree<T>,
}