Struct Optional 

pub struct Optional;

Marker indicating a field may or may not be present (Option).

Trait Implementations

impl Presence for Optional

type OptionOrSelf = Optional

The presence state when combined with an Option.

type Or<Other: Presence> = <Other as Presence>::OptionOrSelf

Result of merging this presence with another.

type RemainderFrom<Source: Presence> = Absent

What remains from Source when extracting Self. Present/Optional → Absent; Absent → Source.

type Output<T> = Option<T>

The container type for values with this presence (T, Option<T>, or PhantomData<T>).

fn or<T, Other: Presence>( self_: <Self as Presence>::Output<T>, other: Other::Output<T>, ) -> <<Self as Presence>::Or<Other> as Presence>::Output<T>

Merge two values, preferring the first if present.

fn option_or_self<T>( option: Option<T>, self_: <Self as Presence>::Output<T>, ) -> <<Self as Presence>::OptionOrSelf as Presence>::Output<T>

Convert an Option into the appropriate presence state.

impl Split<Absent> for Optional

fn split<T>(value: Option<T>) -> (PhantomData<T>, Option<T>)

Split a value into selected and remainder parts.

impl Split<Optional> for Absent

fn split<T>(_value: PhantomData<T>) -> (Option<T>, PhantomData<T>)

Split a value into selected and remainder parts.

impl Split<Optional> for Optional

fn split<T>(value: Option<T>) -> (Option<T>, PhantomData<T>)

Split a value into selected and remainder parts.

impl Split<Optional> for Present

fn split<T>(value: T) -> (Option<T>, PhantomData<T>)

Split a value into selected and remainder parts.

impl TrySplit<Present> for Optional

fn try_split<T>(value: Option<T>) -> Result<(T, PhantomData<T>), Option<T>>

Try to split a value into selected and remainder parts.