fn size_hint(&self) -> (usize, Option<usize>) {
        match self {
            NodeIterHelper::Empty => (0, Some(0)),
            NodeIterHelper::Single(_) => (1, Some(1)),
            NodeIterHelper::Vec(iter) => iter.size_hint(),
        }
    }
// Must return the upper bound returned by Node::len.
Must return the upper bound returned by Node::len.
Must return the upper bound returned by Node :: len .
fn size_hint(&self) -> (usize, Option<usize>) {
        match self {
            NodeIterHelper::Empty => (0, Some(0)),
            NodeIterHelper::Single(_) => (1, Some(1)),
            NodeIterHelper::Vec(iter) => iter.size_hint(),
        }
    }
fn size_hint ( & self ) -> ( usize , Option < usize > ) { match self { NodeIterHelper :: Empty => ( 0 , Some ( 0 ) ) , NodeIterHelper :: Single ( _ ) => ( 1 , Some ( 1 ) ) , NodeIterHelper :: Vec ( iter ) => iter . size_hint ( ) , } }
Must return the upper bound returned by Node::len.
Must return the upper bound returned by Node :: len .
&self