Create a variant object whose contained value is direct-initialized from the specified t. The alternative selected is the best match among all alternatives for which the expression t_ALT_TYPE x[]= {std::forward<t_TYPE>(t)}; is well formed, and this constructor participates in overload resolution only if there is a unique best matching alternative and that alternative is constructible from t. If this variant is allocator-aware, the specified allocator is used to supply memory. Note that the cv-qualification of an alternative type does not affect how well the alternative type matches an argument type.
Declared in <bslstl_variant.h>
template<class t_TYPE>
variant(
std::allocator_arg_t,
allocator_type allocator,
t_TYPE&& t);