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diff --git a/vendor/itertools/src/sources.rs b/vendor/itertools/src/sources.rs
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+//! Iterators that are sources (produce elements from parameters,
+//! not from another iterator).
+#![allow(deprecated)]
+
+use std::fmt;
+use std::mem;
+
+/// Creates a new unfold source with the specified closure as the "iterator
+/// function" and an initial state to eventually pass to the closure
+///
+/// `unfold` is a general iterator builder: it has a mutable state value,
+/// and a closure with access to the state that produces the next value.
+///
+/// This more or less equivalent to a regular struct with an [`Iterator`]
+/// implementation, and is useful for one-off iterators.
+///
+/// ```
+/// // an iterator that yields sequential Fibonacci numbers,
+/// // and stops at the maximum representable value.
+///
+/// use itertools::unfold;
+///
+/// let mut fibonacci = unfold((1u32, 1u32), |(x1, x2)| {
+///     // Attempt to get the next Fibonacci number
+///     let next = x1.saturating_add(*x2);
+///
+///     // Shift left: ret <- x1 <- x2 <- next
+///     let ret = *x1;
+///     *x1 = *x2;
+///     *x2 = next;
+///
+///     // If addition has saturated at the maximum, we are finished
+///     if ret == *x1 && ret > 1 {
+///         None
+///     } else {
+///         Some(ret)
+///     }
+/// });
+///
+/// itertools::assert_equal(fibonacci.by_ref().take(8),
+///                         vec![1, 1, 2, 3, 5, 8, 13, 21]);
+/// assert_eq!(fibonacci.last(), Some(2_971_215_073))
+/// ```
+#[deprecated(
+    note = "Use [std::iter::from_fn](https://doc.rust-lang.org/std/iter/fn.from_fn.html) instead",
+    since = "0.13.0"
+)]
+pub fn unfold<A, St, F>(initial_state: St, f: F) -> Unfold<St, F>
+where
+    F: FnMut(&mut St) -> Option<A>,
+{
+    Unfold {
+        f,
+        state: initial_state,
+    }
+}
+
+impl<St, F> fmt::Debug for Unfold<St, F>
+where
+    St: fmt::Debug,
+{
+    debug_fmt_fields!(Unfold, state);
+}
+
+/// See [`unfold`](crate::unfold) for more information.
+#[derive(Clone)]
+#[must_use = "iterators are lazy and do nothing unless consumed"]
+#[deprecated(
+    note = "Use [std::iter::FromFn](https://doc.rust-lang.org/std/iter/struct.FromFn.html) instead",
+    since = "0.13.0"
+)]
+pub struct Unfold<St, F> {
+    f: F,
+    /// Internal state that will be passed to the closure on the next iteration
+    pub state: St,
+}
+
+impl<A, St, F> Iterator for Unfold<St, F>
+where
+    F: FnMut(&mut St) -> Option<A>,
+{
+    type Item = A;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        (self.f)(&mut self.state)
+    }
+}
+
+/// An iterator that infinitely applies function to value and yields results.
+///
+/// This `struct` is created by the [`iterate()`](crate::iterate) function.
+/// See its documentation for more.
+#[derive(Clone)]
+#[must_use = "iterators are lazy and do nothing unless consumed"]
+pub struct Iterate<St, F> {
+    state: St,
+    f: F,
+}
+
+impl<St, F> fmt::Debug for Iterate<St, F>
+where
+    St: fmt::Debug,
+{
+    debug_fmt_fields!(Iterate, state);
+}
+
+impl<St, F> Iterator for Iterate<St, F>
+where
+    F: FnMut(&St) -> St,
+{
+    type Item = St;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        let next_state = (self.f)(&self.state);
+        Some(mem::replace(&mut self.state, next_state))
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (usize::MAX, None)
+    }
+}
+
+/// Creates a new iterator that infinitely applies function to value and yields results.
+///
+/// ```
+/// use itertools::iterate;
+///
+/// itertools::assert_equal(iterate(1, |i| i % 3 + 1).take(5), vec![1, 2, 3, 1, 2]);
+/// ```
+///
+/// **Panics** if compute the next value does.
+///
+/// ```should_panic
+/// # use itertools::iterate;
+/// let mut it = iterate(25u32, |x| x - 10).take_while(|&x| x > 10);
+/// assert_eq!(it.next(), Some(25)); // `Iterate` holds 15.
+/// assert_eq!(it.next(), Some(15)); // `Iterate` holds 5.
+/// it.next(); // `5 - 10` overflows.
+/// ```
+///
+/// You can alternatively use [`core::iter::successors`] as it better describes a finite iterator.
+pub fn iterate<St, F>(initial_value: St, f: F) -> Iterate<St, F>
+where
+    F: FnMut(&St) -> St,
+{
+    Iterate {
+        state: initial_value,
+        f,
+    }
+}