Generic C++ copy between objects that support copy construction and those that don't

A long story short, I'm working on a container that can contain either copy constructable objects, or those that don't. Something like:

using AllocTraits = std::allocator_traits<Alloc>;
template <typename T>
void foo(T *to T *from, size_t n, Alloc alloc) {
  for (size_t i = 0; i < n; ++i) {
    AllocTraits::construct(alloc, to++, *from++);
  }
}

The problem I have is that my T can support either copy constructable classes or moveable classes. So, I moved to a slightly different approach:

using AllocTraits = std::allocator_traits<Alloc>;
template <typename T>
void foo(T *to T *from, size_t n, Alloc alloc) {
  auto mov_to = std::make_move_iterator(to);
  for (size_t i = 0; i < n; ++i) {
    AllocTraits::construct(alloc, mov_to++, *from++);
  }
}

But this will call T::(T&&), when I'd rather call T::T(const T&) if the type supports it.

How can I write foo so that it will call T::T(const T&) as a default, but move to T::T(T&&) otherwise?