Python-like loop enumeration in C++

enumerate.h

#include <tuple>

template <typename T> class enumerate {
  struct iterator {
    using iter_type = decltype(std::declval<T>().begin());

  private:
    friend class enumerate;
    iterator(const std::size_t &i, const iter_type &iter)
        : i_(i), iter_(iter) {}
    std::size_t i_;
    iter_type iter_;

  public:
    std::tuple<const std::size_t,
               typename std::iterator_traits<iter_type>::reference>
    operator*() {
      return {i_, *iter_};
    }

    bool operator!=(const iterator &other) { return other.iter_ != iter_; }

    auto operator++() {
      ++i_;
      ++iter_;
      return *this;
    }
  };

public:
  template <typename U>
  enumerate(U &&container) : container_(std::forward<U>(container)) {}

  auto begin() { return iterator{0, container_.begin()}; }

  auto end() { return iterator{container_.size(), container_.end()}; }

private:
  T container_;
};

template <typename U>
enumerate(U &&container)
    ->enumerate<std::enable_if_t<
        !std::is_rvalue_reference_v<decltype(std::forward<U>(container))>, U &>>;

template <typename U>
enumerate(U &&container)
    ->enumerate<std::enable_if_t<
        std::is_rvalue_reference_v<decltype(std::forward<U>(container))>,
        const U>>;