[depr.variant]

# Annex D (normative) Compatibility features [[depr]](./#depr)

## D.16 Variant [depr.variant]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L592)

The header [<variant>](variant.syn#header:%3cvariant%3e "22.6.2 Header <variant> synopsis [variant.syn]") 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>;}

[ð](#itemdecl:1)

`template<class T> struct variant_size<volatile T>;
template<class T> struct variant_size<const volatile T>;
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L610)

Let VS denote variant_size<T> of the cv-unqualified type T[.](#2.sentence-1)

Then specializations of each of the two templates meet
the [*Cpp17UnaryTypeTrait*](meta.rqmts#:Cpp17UnaryTypeTrait "21.3.2 Requirements [meta.rqmts]") requirements
with a base characteristic of integral_constant<size_t, VS​::​value>[.](#2.sentence-2)

[ð](#itemdecl:2)

`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>;
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L624)

Let VA denote variant_alternative<I, T> of the cv-unqualified type T[.](#3.sentence-1)

Then specializations of each of the two templates meet
the [*Cpp17TransformationTrait*](meta.rqmts#:Cpp17TransformationTrait "21.3.2 Requirements [meta.rqmts]") requirements
with a member typedef type that names the following type:

- [(3.1)](#3.1)

for the first specialization, add_volatile_t<VA​::​type>, and

- [(3.2)](#3.2)

for the second specialization, add_cv_t<VA​::​type>[.](#3.sentence-2)
