template<typename A1>
v8::Handle<v8::Value> __constructor1(v8::Arguments args) {
    return createObject(args[0] as A1);
}

template<typename A1, typename A2>
v8::Handle<v8::Value> _constructor2(v8::Arguments args) {
    return createObject(args[0] as A1, args[1] as A2);
}

...

template<typename A1>
void def_constructor() {
     v8::FunctionTemplate::New(&__constructor1<A1>);
}

template<typename A1, typename A2>
void def_constructor() {
     v8::FunctionTemplate::New(&__constructor2<A1, A2>);
}