Parameterized types and return values in D why does this not work?

Question

OK, it seems my prior problem is now resolved (I've left it below for reference). However, yet another one crops up - again, seemingly something I'm missing. Further up in this code, I declared the following:

private:

T _data;
BinaryTree!(T) _left; 
BinaryTree!(T) _right;

Then after this, I declared these:

public:
@property T data() {return _data;}
@property BinaryTree!(T) left() {return _left;}
@property BinaryTree!(T) right() {return _right;}

Then, I implemented the following function:

void add (T data) {
    BinaryTree!(T) nearest = findNearest(this, data);
    if (nearest.data > data) {
        nearest.left = new BinaryTree!(T) (data);
    }
    else {
        nearest.right = new BinaryTree!(T) (data);
    }
}

The compiler is protesting that nearest.left and nearest.right aren't properties, although as nearest is a BinaryTree!(T), this seems rather odd. What am I missing?

---

OLD PROBLEM:

I've recently gotten into D, and was trying to build a binary tree implementation as a way of testing what I've learned by reading about it. Now, I started by declaring it as follows:

class BinaryTree(T)

I figured this would allow me to parametrize some of the stuff the class holds. More specifically:

T _data;
BinaryTree!(T) _left;
BinaryTree!(T) _right;

Now, I then tried writing this:

BinaryTree!(T) findNearest (BinaryTree(T) x, T key) {
    if (x.hasNoChildren || x.data == key) {
        return x; //found it
    }
    else {
        auto compare = x.data;
        if (compare > key) {
            return find (x.left, key);
        }
        else {
            return find (x.right, key);
        }
    }
}

After this, the compiler loudly complained about my function not having a return type. What am I doing wrong here? If it helps to explain, I come from a Java background, and I'm using the dmd compiler inside of Xamarin Studio.

Answer 1

The only error I can see is a missing ! in the function parameter:

BinaryTree!(T) findNearest (BinaryTree(T) x, T key) {

should be

BinaryTree!(T) findNearest (BinaryTree!(T) x, T key) {

The rest looks fine to me.