Return the index of the alternative currently managed by this variant object, or bsl::variant_npos if this object is valueless by exception. This method differs from the standard in the following way: * constexpr is not implemented This is because no constructors are currently constexpr and there is no way to test the constexpr property of this function.
Declared in <bslstl_variant.h>
std::size_t
index() const noexcept;