gistfile1.d

class RedBlackTree(alias less)
{
    int a;
    struct Range
    {
        auto @property empty()
        {
            return a;
        }
    }
 
    Range opSlice()
    {
        return Range();
    }
}
 
void main()
{
    void a(){}
    auto t = new RedBlackTree!(a);
}