[variant.specalg]

template<class. Types>
  constexpr void swap(variant<Types..>& v, variant<Types..>& w) noexcept(see below);

Constraints: is_move_constructible_v<

T {i > & & is_swappable_v < T {i > is true for all i .}_{i >}}_{i > & & is_swappable_v < T {i > is true for all i .}_{i >}}

Remarks: The exception specification is equivalent to noexcept(v.swap(w)).

22 General utilities library [utilities]