This metafunction calculates the type of the alternative whose index is (template parameter) t_INDEX in the possibly cv-qualified bsl::variant type of (template parameter) t_TYPE. If t_TYPE is cv-qualified, its cv-qualifiers are applied to the alternative.
Declared in <bslstl_variant.h>
template<
std::size_t t_INDEX,
class t_TYPE>
struct variant_alternative;