bsl::optional::optional

Create a disengaged optional object if the specified original object is disengaged, and an optional object with the value of original.value() moved and converted to t_TYPE otherwise. Use the allocator from original to supply memory if t_ANY_TYPE is a non‐const version of t_TYPE; otherwise, use the currently installed default allocator. original is left in a valid but unspecified state. Note that this constructor participates in overload resolution only when t_TYPE is constructible from an xvalue of t_ANY_TYPE, and is implicit only when an xvalue of 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.