From 9918693037dce8aa4bb6f08741b6812923486c18 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 19 Jun 2024 11:26:03 +0200
Subject: Merging upstream version 1.76.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 vendor/itertools/src/with_position.rs | 49 +++++++++++++++++++++++++++--------
 1 file changed, 38 insertions(+), 11 deletions(-)

(limited to 'vendor/itertools/src/with_position.rs')

diff --git a/vendor/itertools/src/with_position.rs b/vendor/itertools/src/with_position.rs
index dda9b25dc..89cddeb8a 100644
--- a/vendor/itertools/src/with_position.rs
+++ b/vendor/itertools/src/with_position.rs
@@ -1,4 +1,4 @@
-use std::iter::{Fuse,Peekable, FusedIterator};
+use std::iter::{Fuse, FusedIterator, Peekable};
 
 /// An iterator adaptor that wraps each element in an [`Position`].
 ///
@@ -7,22 +7,25 @@ use std::iter::{Fuse,Peekable, FusedIterator};
 /// See [`.with_position()`](crate::Itertools::with_position) for more information.
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 pub struct WithPosition<I>
-    where I: Iterator,
+where
+    I: Iterator,
 {
     handled_first: bool,
     peekable: Peekable<Fuse<I>>,
 }
 
 impl<I> Clone for WithPosition<I>
-    where I: Clone + Iterator,
-          I::Item: Clone,
+where
+    I: Clone + Iterator,
+    I::Item: Clone,
 {
     clone_fields!(handled_first, peekable);
 }
 
 /// Create a new `WithPosition` iterator.
 pub fn with_position<I>(iter: I) -> WithPosition<I>
-    where I: Iterator,
+where
+    I: Iterator,
 {
     WithPosition {
         handled_first: false,
@@ -34,7 +37,7 @@ pub fn with_position<I>(iter: I) -> WithPosition<I>
 /// Indicates the position of this element in the iterator results.
 ///
 /// See [`.with_position()`](crate::Itertools::with_position) for more information.
-#[derive(Copy, Clone, Debug, PartialEq)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Position {
     /// This is the first element.
     First,
@@ -78,11 +81,35 @@ impl<I: Iterator> Iterator for WithPosition<I> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.peekable.size_hint()
     }
+
+    fn fold<B, F>(mut self, mut init: B, mut f: F) -> B
+    where
+        F: FnMut(B, Self::Item) -> B,
+    {
+        if let Some(mut head) = self.peekable.next() {
+            if !self.handled_first {
+                // The current head is `First` or `Only`,
+                // it depends if there is another item or not.
+                match self.peekable.next() {
+                    Some(second) => {
+                        let first = std::mem::replace(&mut head, second);
+                        init = f(init, (Position::First, first));
+                    }
+                    None => return f(init, (Position::Only, head)),
+                }
+            }
+            // Have seen the first item, and there's something left.
+            init = self.peekable.fold(init, |acc, mut item| {
+                std::mem::swap(&mut head, &mut item);
+                f(acc, (Position::Middle, item))
+            });
+            // The "head" is now the last item.
+            init = f(init, (Position::Last, head));
+        }
+        init
+    }
 }
 
-impl<I> ExactSizeIterator for WithPosition<I>
-    where I: ExactSizeIterator,
-{ }
+impl<I> ExactSizeIterator for WithPosition<I> where I: ExactSizeIterator {}
 
-impl<I: Iterator> FusedIterator for WithPosition<I> 
-{}
+impl<I: Iterator> FusedIterator for WithPosition<I> {}
-- 
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