[depr.variant]

The header <variant> has the following additions: namespace std { template<class T> struct variant_size<volatile T>; template<class T> struct variant_size<const volatile T>; template<size_t I, class T> struct variant_alternative<I, volatile T>; template<size_t I, class T> struct variant_alternative<I, const volatile T>; }

Let VS denote variant_size<T> of the cv-unqualified type T.

Then specializations of each of the two templates meet the Cpp17UnaryTypeTrait requirements with a base characteristic of integral_constant<size_t, VS::value>.

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template<size_t I, class T> struct variant_alternative<I, volatile T>;
template<size_t I, class T> struct variant_alternative<I, const volatile T>;

Let VA denote variant_alternative<I, T> of the cv-unqualified type T.

Then specializations of each of the two templates meet the Cpp17TransformationTrait requirements with a member typedef type that names the following type:

(3.1)
for the first specialization, volatile VA::type, and
(3.2)
for the second specialization, const volatile VA::type.