eg.cpp

bool exists = false;

class Tester {
  Tester() = default;
  Tester& operator=(const Tester&) {
    if (exists)
      throw std::runtime_error{};
    else
      exists = true;
  }
};

int main() {
  Vector<Tester> v;
  v.push_back(Tester{}); // succeeds
  try {
    v.push_back(Tester{}); // std::copy fails
  } catch (...) {}
  std::cout << v.size() << '\n';
}