It's a bit tricky to get constructor and assignment operator accepting forward reference (singular or variadic) right

forward_ref_ctor_assignment.cpp

#include <type_traits>
#include <utility>

struct Bar {};

// Note about `is_convertible<T&&, Foo>`. `T&&` is essential there!
struct Foo
{
    template<class T, class = typename std::enable_if<!std::is_convertible<T&&, Foo>::value>::type>
    Foo(T&& t) {}

    Foo(Bar&& bar) {}

    template<class T, class = typename std::enable_if<!std::is_convertible<T&&, Foo>::value>::type>
    Foo& operator= (T&& t) { return *this; }

    Foo& operator= (Bar&& bar) {  return *this; }
};


// Type your code here, or load an example.
int square(int num) {
    Bar bar1, bar2;

    Foo foo1(bar1);
    Foo foo2(std::move(bar1));

    foo1 = bar2;
    foo2 = std::move(bar2);

    (void) foo1; (void) foo2;
    return 0;
}