copy_or_move.cpp

#include <type_traits>
#include <iostream>

using namespace std;

template <typename Iterator>
using value_type = typename Iterator::value_type;

template <typename Iterator, typename Data>
auto copy_or_move(Iterator begin, Iterator end, Data& new_memory)
  -> enable_if_t< ! is_nothrow_move_constructible<value_type<Iterator>>::value>
{
  std::cout << "copy" << std::endl;
}

template <typename Iterator, typename Data>
auto copy_or_move(Iterator begin, Iterator end, Data& new_memory)
  -> enable_if_t<is_nothrow_move_constructible<value_type<Iterator>>::value>
{
  std::cout << "move" << std::endl;
}

struct A
{
  A(A&&);
};

struct B
{
  B(B&&) noexcept;
};

template<typename T>
struct I
{
  using value_type = T;
};

int main()
{
  auto ia = I<A>{};
  copy_or_move(ia, ia, std::cout);

  auto ib = I<B>{};
  copy_or_move(ib, ib, std::cout);
}