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diff --git a/third_party/rust/rayon/src/iter/repeat.rs b/third_party/rust/rayon/src/iter/repeat.rs
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+++ b/third_party/rust/rayon/src/iter/repeat.rs
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+use super::plumbing::*;
+use super::*;
+use std::iter;
+use std::usize;
+
+/// Iterator adaptor for [the `repeat()` function](fn.repeat.html).
+#[derive(Debug, Clone)]
+pub struct Repeat<T: Clone + Send> {
+    element: T,
+}
+
+/// Creates a parallel iterator that endlessly repeats `elt` (by
+/// cloning it). Note that this iterator has "infinite" length, so
+/// typically you would want to use `zip` or `take` or some other
+/// means to shorten it, or consider using
+/// [the `repeatn()` function](fn.repeatn.html) instead.
+///
+/// # Examples
+///
+/// ```
+/// use rayon::prelude::*;
+/// use rayon::iter::repeat;
+/// let x: Vec<(i32, i32)> = repeat(22).zip(0..3).collect();
+/// assert_eq!(x, vec![(22, 0), (22, 1), (22, 2)]);
+/// ```
+pub fn repeat<T: Clone + Send>(elt: T) -> Repeat<T> {
+    Repeat { element: elt }
+}
+
+impl<T> Repeat<T>
+where
+    T: Clone + Send,
+{
+    /// Takes only `n` repeats of the element, similar to the general
+    /// [`take()`](trait.IndexedParallelIterator.html#method.take).
+    ///
+    /// The resulting `RepeatN` is an `IndexedParallelIterator`, allowing
+    /// more functionality than `Repeat` alone.
+    pub fn take(self, n: usize) -> RepeatN<T> {
+        repeatn(self.element, n)
+    }
+
+    /// Iterates tuples, repeating the element with items from another
+    /// iterator, similar to the general
+    /// [`zip()`](trait.IndexedParallelIterator.html#method.zip).
+    pub fn zip<Z>(self, zip_op: Z) -> Zip<RepeatN<T>, Z::Iter>
+    where
+        Z: IntoParallelIterator,
+        Z::Iter: IndexedParallelIterator,
+    {
+        let z = zip_op.into_par_iter();
+        let n = z.len();
+        self.take(n).zip(z)
+    }
+}
+
+impl<T> ParallelIterator for Repeat<T>
+where
+    T: Clone + Send,
+{
+    type Item = T;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        let producer = RepeatProducer {
+            element: self.element,
+        };
+        bridge_unindexed(producer, consumer)
+    }
+}
+
+/// Unindexed producer for `Repeat`.
+struct RepeatProducer<T: Clone + Send> {
+    element: T,
+}
+
+impl<T: Clone + Send> UnindexedProducer for RepeatProducer<T> {
+    type Item = T;
+
+    fn split(self) -> (Self, Option<Self>) {
+        (
+            RepeatProducer {
+                element: self.element.clone(),
+            },
+            Some(RepeatProducer {
+                element: self.element,
+            }),
+        )
+    }
+
+    fn fold_with<F>(self, folder: F) -> F
+    where
+        F: Folder<T>,
+    {
+        folder.consume_iter(iter::repeat(self.element))
+    }
+}
+
+/// Iterator adaptor for [the `repeatn()` function](fn.repeatn.html).
+#[derive(Debug, Clone)]
+pub struct RepeatN<T: Clone + Send> {
+    element: T,
+    count: usize,
+}
+
+/// Creates a parallel iterator that produces `n` repeats of `elt`
+/// (by cloning it).
+///
+/// # Examples
+///
+/// ```
+/// use rayon::prelude::*;
+/// use rayon::iter::repeatn;
+/// let x: Vec<(i32, i32)> = repeatn(22, 3).zip(0..3).collect();
+/// assert_eq!(x, vec![(22, 0), (22, 1), (22, 2)]);
+/// ```
+pub fn repeatn<T: Clone + Send>(elt: T, n: usize) -> RepeatN<T> {
+    RepeatN {
+        element: elt,
+        count: n,
+    }
+}
+
+impl<T> ParallelIterator for RepeatN<T>
+where
+    T: Clone + Send,
+{
+    type Item = T;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        Some(self.count)
+    }
+}
+
+impl<T> IndexedParallelIterator for RepeatN<T>
+where
+    T: Clone + Send,
+{
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        callback.callback(RepeatNProducer {
+            element: self.element,
+            count: self.count,
+        })
+    }
+
+    fn len(&self) -> usize {
+        self.count
+    }
+}
+
+/// Producer for `RepeatN`.
+struct RepeatNProducer<T: Clone + Send> {
+    element: T,
+    count: usize,
+}
+
+impl<T: Clone + Send> Producer for RepeatNProducer<T> {
+    type Item = T;
+    type IntoIter = Iter<T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        Iter {
+            element: self.element,
+            count: self.count,
+        }
+    }
+
+    fn split_at(self, index: usize) -> (Self, Self) {
+        (
+            RepeatNProducer {
+                element: self.element.clone(),
+                count: index,
+            },
+            RepeatNProducer {
+                element: self.element,
+                count: self.count - index,
+            },
+        )
+    }
+}
+
+/// Iterator for `RepeatN`.
+///
+/// This is conceptually like `std::iter::Take<std::iter::Repeat<T>>`, but
+/// we need `DoubleEndedIterator` and unconditional `ExactSizeIterator`.
+struct Iter<T: Clone> {
+    element: T,
+    count: usize,
+}
+
+impl<T: Clone> Iterator for Iter<T> {
+    type Item = T;
+
+    #[inline]
+    fn next(&mut self) -> Option<T> {
+        if self.count > 0 {
+            self.count -= 1;
+            Some(self.element.clone())
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.count, Some(self.count))
+    }
+}
+
+impl<T: Clone> DoubleEndedIterator for Iter<T> {
+    #[inline]
+    fn next_back(&mut self) -> Option<T> {
+        self.next()
+    }
+}
+
+impl<T: Clone> ExactSizeIterator for Iter<T> {
+    #[inline]
+    fn len(&self) -> usize {
+        self.count
+    }
+}