struct AnyVtable{
    String* (*toString)(Any* thisobj);
    ...
    Any (*call)(Any* thisobj, RestParams params);
};

struct Any{
    AnyVtable* vtable;
    union{
        Object* object;
        ...
    };
};


Any fnc_wrapper(Any* closure, RestParams params){
    if ( params.length < 2 ){
        throw new TypeError("not enough arguments, expected no less than 2");
    }
    if ( params.length > 2 ){
        throw new TypeError("too many arguments, expected no more than 2");
    }
    int a0 = Any::unwrapInt(params[0]);
    double a1 = Any::unwrapNumber(params[1]);
    Foo* this_object = (Foo*)closure->object;
    return Any::wrap(this_object->fnc(a0, a1));
}


AnyVtable Foo_fnc_vtable = {
    /*toString = */ [](Any*) -> String*{
        return new String("Foo::fnc");
    },
    ...
    /*call = */ fnc_wrapper
};