struct Aware(T) {
    bool changed;
    alias data this;


    @property
    ref T data() {
        return d;
    }

    @property
    void data(T assgn) {
        if(d != assgn) {
            d = assgn;
            changed = true;
        }
    }
private:
    T d;
}

class Test(T) {
    T x;
}

unittest {
    Aware!(Test!int) test;
    test = new Test!int;
    test.x = 5;
    assert(test.x == 5);
}