use core::iter::FusedIterator;

use super::node::{self, ForceResult::*};
use super::search::{SearchResult, SearchStack};
use super::Root;
use crate::alloc::Allocator;
use crate::borrow::Borrow;
use crate::collections::TryReserveError;
use crate::hash::{BuildHasher, HashMap, HashSet};
use crate::vec::Vec;
use core::borrow::Borrow;
use core::cmp::Ordering;
use core::fmt::{self, Debug};
use core::hash::{Hash, Hasher};
use core::iter::{Chain, FromIterator, Peekable};
use core::mem::{self, ManuallyDrop};
use core::ops::{BitAnd, BitOr, BitXor, Sub};
use core::ptr;
use core::slice;
use core::vec;

impl<'a, T: Copy + Ord, B: BuildHasher> Iterator for SymmetricDifference<'a, T, B> {
    type Item = &'a T;

    fn next(&mut self) -> Option<Self::Item> {
        // ...existing code...
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        // ...existing code...
    }
}

// FusedIterator is safe for SymmetricDifference only if we can guarantee that once next() returns None,
// subsequent calls will continue to return None. This needs to be verified by examining
// the implementation details.
//
// The implementation should be checked to ensure that once both input iterators
// are exhausted, the SymmetricDifference iterator will consistently return None.
// impl<'a, T: Copy + Ord, B: BuildHasher> FusedIterator for SymmetricDifference<'a, T, B> {}