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    use crate::iter::adapters::{zip::try_get_unchecked, TrustedRandomAccess};
    use crate::iter::{FusedIterator, TrustedLen};
    use crate::ops::Try;

    /// An iterator that clones the elements of an underlying iterator.
    ///
    /// This `struct` is created by the [`cloned`] method on [`Iterator`]. See its
    /// documentation for more.
    ///
    /// [`cloned`]: Iterator::cloned
    /// [`Iterator`]: trait.Iterator.html
    #[stable(feature = "iter_cloned", since = "1.1.0")]
    #[must_use = "iterators are lazy and do nothing unless consumed"]
    #[derive(Clone, Debug)]
    pub struct Cloned<I> {
        it: I,
    }

    impl<I> Cloned<I> {
        pub(in crate::iter) fn new(it: I) -> Cloned<I> {
            Cloned { it }
        }
    }

    fn clone_try_fold<T: Clone, Acc, R>(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R {
        move |acc, elt| f(acc, elt.clone())
    }

    #[stable(feature = "iter_cloned", since = "1.1.0")]
    impl<'a, I, T: 'a> Iterator for Cloned<I>
    where
        I: Iterator<Item = &'a T>,
        T: Clone,
    {
        type Item = T;

        fn next(&mut self) -> Option<T> {
            self.it.next().cloned()
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            self.it.size_hint()
        }

        fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
        where
            Self: Sized,
            F: FnMut(B, Self::Item) -> R,
            R: Try<Ok = B>,
        {
            self.it.try_fold(init, clone_try_fold(f))
        }

        fn fold<Acc, F>(self, init: Acc, f: F) -> Acc
        where
            F: FnMut(Acc, Self::Item) -> Acc,
        {
            self.it.map(T::clone).fold(init, f)
        }

        unsafe fn __iterator_get_unchecked(&mut self, idx: usize) -> T
        where
            Self: TrustedRandomAccess,
        {
            // SAFETY: the caller must uphold the contract for
            // `Iterator::__iterator_get_unchecked`.
            unsafe { try_get_unchecked(&mut self.it, idx).clone() }
        }
    }

    #[stable(feature = "iter_cloned", since = "1.1.0")]
    impl<'a, I, T: 'a> DoubleEndedIterator for Cloned<I>
    where
        I: DoubleEndedIterator<Item = &'a T>,
        T: Clone,
    {
        fn next_back(&mut self) -> Option<T> {
            self.it.next_back().cloned()
        }

        fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
        where
            Self: Sized,
            F: FnMut(B, Self::Item) -> R,
            R: Try<Ok = B>,
        {
            self.it.try_rfold(init, clone_try_fold(f))
        }

        fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc
        where
            F: FnMut(Acc, Self::Item) -> Acc,
        {
            self.it.map(T::clone).rfold(init, f)
        }
    }

    #[stable(feature = "iter_cloned", since = "1.1.0")]
    impl<'a, I, T: 'a> ExactSizeIterator for Cloned<I>
    where
        I: ExactSizeIterator<Item = &'a T>,
        T: Clone,
    {
        fn len(&self) -> usize {
            self.it.len()
        }

        fn is_empty(&self) -> bool {
            self.it.is_empty()
        }
    }

    #[stable(feature = "fused", since = "1.26.0")]
    impl<'a, I, T: 'a> FusedIterator for Cloned<I>
    where
        I: FusedIterator<Item = &'a T>,
        T: Clone,
    {
    }

    #[doc(hidden)]
    #[unstable(feature = "trusted_random_access", issue = "none")]
    unsafe impl<I> TrustedRandomAccess for Cloned<I>
    where
        I: TrustedRandomAccess,
    {
        #[inline]
        fn may_have_side_effect() -> bool {
            true
        }
    }

    #[unstable(feature = "trusted_len", issue = "37572")]
    unsafe impl<'a, I, T: 'a> TrustedLen for Cloned<I>
    where
        I: TrustedLen<Item = &'a T>,
        T: Clone,
    {
    }