From e77acf7d27f7690f6cdb18d2ce68a37cbabd884c Mon Sep 17 00:00:00 2001
From: Ian Wahbe <ian@wahbe.com>
Date: Tue, 29 Jun 2021 15:35:14 +0200
Subject: [PATCH] Add non-mutable methods to `Cursor`

---
 library/alloc/src/collections/linked_list.rs       | 14 ++++++++++++++
 library/alloc/src/collections/linked_list/tests.rs |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/library/alloc/src/collections/linked_list.rs b/library/alloc/src/collections/linked_list.rs
index a21eedf02f1..4eecf5703a4 100644
--- a/library/alloc/src/collections/linked_list.rs
+++ b/library/alloc/src/collections/linked_list.rs
@@ -1243,6 +1243,20 @@ impl<'a, T> Cursor<'a, T> {
             prev.map(|prev| &(*prev.as_ptr()).element)
         }
     }
+
+    /// Provides a reference to the front element of the cursor's parent list,
+    /// or None if the list is empty.
+    #[unstable(feature = "linked_list_cursors", issue = "58533")]
+    pub fn front(&self) -> Option<&T> {
+        self.list.front()
+    }
+
+    /// Provides a reference to the back element of the cursor's parent list,
+    /// or None if the list is empty.
+    #[unstable(feature = "linked_list_cursors", issue = "58533")]
+    pub fn back(&self) -> Option<&T> {
+        self.list.back()
+    }
 }
 
 impl<'a, T> CursorMut<'a, T> {
diff --git a/library/alloc/src/collections/linked_list/tests.rs b/library/alloc/src/collections/linked_list/tests.rs
index 429685260fd..45349a7df12 100644
--- a/library/alloc/src/collections/linked_list/tests.rs
+++ b/library/alloc/src/collections/linked_list/tests.rs
@@ -456,6 +456,9 @@ fn test_cursor_pop_front_back() {
     c.move_prev();
     c.move_prev();
     assert_eq!(c.pop_back(), Some(6));
+    let c = c.as_cursor();
+    assert_eq!(c.front(), Some(&2));
+    assert_eq!(c.back(), Some(&5));
     drop(c);
     assert_eq!(ll, (2..6).collect());
     check_links(&ll);