Create a disengaged optional object if the specified original object is disengaged, and an optional object with the value of original.value() converted to t_TYPE otherwise. Use the currently installed default allocator to supply memory. Note that this constructor participates in overload resolution only when t_TYPE is constructible from an lvalue of const t_ANY_TYPE, and is implicit only when an lvalue of const t_ANY_TYPE is implicitly convertible to t_TYPE. This constructor can be called in constant expressions only when neither t_TYPE nor t_ANY_TYPE is allocator-aware.
Declared in <bslstl_optional.h>
template<class t_ANY_TYPE>
constexpr
optional(optional<t_ANY_TYPE> const& original);