message: Delay checking is_swappable<Base> in tagged
diff: @@ -121,17 +121,17 @@ namespace ranges
  static_cast<Base &>(*this) = std::forward<U>(u);
  return *this;
  }
  - template<int dummy_ = 42>
  - RANGES_CXX14_CONSTEXPR meta::if_c<dummy_ == 43 || is_swappable<Base>::value>
  + template<typename B = Base>
  + RANGES_CXX14_CONSTEXPR meta::if_c<is_swappable<B>::value>
  swap(tagged &that)
  - noexcept(is_nothrow_swappable<Base>::value)
  + noexcept(is_nothrow_swappable<B>::value)
  {
  ranges::swap(static_cast<Base &>(*this), static_cast<Base &>(that));
  }
  - template<int dummy_ = 42>
  - friend RANGES_CXX14_CONSTEXPR meta::if_c<dummy_ == 43 || is_swappable<Base>::value>
  + template<typename B = Base>
  + friend RANGES_CXX14_CONSTEXPR meta::if_c<is_swappable<B>::value>
  swap(tagged &x, tagged &y)
  - noexcept(is_nothrow_swappable<Base>::value)
  + noexcept(is_nothrow_swappable<B>::value)
  {
  x.swap(y);
  }
  