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    use core::mem;
    use core::slice;
    use std::rc::Rc;
    use std::vec;

    pub(crate) struct RcVec<T> {
        inner: Rc<Vec<T>>,
    }

    pub(crate) struct RcVecBuilder<T> {
        inner: Vec<T>,
    }

    pub(crate) struct RcVecMut<'a, T> {
        inner: &'a mut Vec<T>,
    }

    #[derive(Clone)]
    pub(crate) struct RcVecIntoIter<T> {
        inner: vec::IntoIter<T>,
    }

    impl<T> RcVec<T> {
        pub fn is_empty(&self) -> bool {
            self.inner.is_empty()
        }

        pub fn len(&self) -> usize {
            self.inner.len()
        }

        pub fn iter(&self) -> slice::Iter<T> {
            self.inner.iter()
        }

        pub fn make_mut(&mut self) -> RcVecMut<T>
        where
            T: Clone,
        {
            RcVecMut {
                inner: Rc::make_mut(&mut self.inner),
            }
        }

        pub fn get_mut(&mut self) -> Option<RcVecMut<T>> {
            let inner = Rc::get_mut(&mut self.inner)?;
            Some(RcVecMut { inner })
        }

        pub fn make_owned(mut self) -> RcVecBuilder<T>
        where
            T: Clone,
        {
            let vec = if let Some(owned) = Rc::get_mut(&mut self.inner) {
                mem::replace(owned, Vec::new())
            } else {
                Vec::clone(&self.inner)
            };
            RcVecBuilder { inner: vec }
        }
    }

    impl<T> RcVecBuilder<T> {
        pub fn new() -> Self {
            RcVecBuilder { inner: Vec::new() }
        }

        pub fn with_capacity(cap: usize) -> Self {
            RcVecBuilder {
                inner: Vec::with_capacity(cap),
            }
        }

        pub fn push(&mut self, element: T) {
            self.inner.push(element);
        }

        pub fn extend(&mut self, iter: impl IntoIterator<Item = T>) {
            self.inner.extend(iter);
        }

        pub fn as_mut(&mut self) -> RcVecMut<T> {
            RcVecMut {
                inner: &mut self.inner,
            }
        }

        pub fn build(self) -> RcVec<T> {
            RcVec {
                inner: Rc::new(self.inner),
            }
        }
    }

    impl<'a, T> RcVecMut<'a, T> {
        pub fn push(&mut self, element: T) {
            self.inner.push(element);
        }

        pub fn extend(&mut self, iter: impl IntoIterator<Item = T>) {
            self.inner.extend(iter);
        }

        pub fn pop(&mut self) -> Option<T> {
            self.inner.pop()
        }

        pub fn as_mut(&mut self) -> RcVecMut<T> {
            RcVecMut { inner: self.inner }
        }
    }

    impl<T> Clone for RcVec<T> {
        fn clone(&self) -> Self {
            RcVec {
                inner: Rc::clone(&self.inner),
            }
        }
    }

    impl<T> IntoIterator for RcVecBuilder<T> {
        type Item = T;
        type IntoIter = RcVecIntoIter<T>;

        fn into_iter(self) -> Self::IntoIter {
            RcVecIntoIter {
                inner: self.inner.into_iter(),
            }
        }
    }

    impl<T> Iterator for RcVecIntoIter<T> {
        type Item = T;

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

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