fn size_hint(&self) -> (usize, Option<usize>) {
        match self {
            Self::Iterator(iter) => iter.iter.size_hint(),
            Self::DoubleEndedIterator(iter) => iter.iter.size_hint(),
            Self::Map(iter) => iter.size_hint(),
            Self::FlatMap(iter) => iter.size_hint(),
            Self::Filter(iter) => iter.size_hint(),
            Self::Rev(iter) => iter.size_hint(),
            Self::Chain(iter) => iter.size_hint(),
            Self::Enumerate(iter) => iter.size_hint(),
            Self::Skip(iter) => iter.size_hint(),
            Self::Take(iter) => iter.size_hint(),
            Self::Peekable(iter) => iter.size_hint(),
            Self::Empty => (0, Some(0)),
            Self::Once(..) => (1, Some(1)),
        }
    }
/// The length of the remaining iterator.
The length of the remaining iterator.
The length of the remaining iterator .
fn size_hint(&self) -> (usize, Option<usize>) {
        match self {
            Self::Iterator(iter) => iter.iter.size_hint(),
            Self::DoubleEndedIterator(iter) => iter.iter.size_hint(),
            Self::Map(iter) => iter.size_hint(),
            Self::FlatMap(iter) => iter.size_hint(),
            Self::Filter(iter) => iter.size_hint(),
            Self::Rev(iter) => iter.size_hint(),
            Self::Chain(iter) => iter.size_hint(),
            Self::Enumerate(iter) => iter.size_hint(),
            Self::Skip(iter) => iter.size_hint(),
            Self::Take(iter) => iter.size_hint(),
            Self::Peekable(iter) => iter.size_hint(),
            Self::Empty => (0, Some(0)),
            Self::Once(..) => (1, Some(1)),
        }
    }
fn size_hint ( & self ) -> ( usize , Option < usize > ) { match self { Self :: Iterator ( iter ) => iter . iter . size_hint ( ) , Self :: DoubleEndedIterator ( iter ) => iter . iter . size_hint ( ) , Self :: Map ( iter ) => iter . size_hint ( ) , Self :: FlatMap ( iter ) => iter . size_hint ( ) , Self :: Filter ( iter ) => iter . size_hint ( ) , Self :: Rev ( iter ) => iter . size_hint ( ) , Self :: Chain ( iter ) => iter . size_hint ( ) , Self :: Enumerate ( iter ) => iter . size_hint ( ) , Self :: Skip ( iter ) => iter . size_hint ( ) , Self :: Take ( iter ) => iter . size_hint ( ) , Self :: Peekable ( iter ) => iter . size_hint ( ) , Self :: Empty => ( 0 , Some ( 0 ) ) , Self :: Once ( .. ) => ( 1 , Some ( 1 ) ) , } }
The length of the remaining iterator.
The length of the remaining iterator .
&self
&self