Need 'this' to access 'opCall'? Was I trying to?

[Mehrdad]

struct Adder {
    int v;
    auto opCall(int x) { return x + v; }
}

auto adder(int v) {
    return Adder(v);  // How do I call the constructor??
}

int main() {
    auto a = adder(5);
}