Auto merge of #31210 - Manishearth:rollup, r=Manishearth

- Successful merges: #31152, #31184, #31189, #31192, #31197, #31199, #31201
- Failed merges:

2 files changed, 9 insertions, 1 deletions

diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index 789b75836d0..6041355e9db 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -414,7 +414,9 @@ impl<T: ?Sized> RefCell<T> {
     ///
     /// let c = RefCell::new(5);
     ///
-    /// let borrowed_five = c.borrow_mut();
+    /// *c.borrow_mut() = 7;
+    ///
+    /// assert_eq!(*c.borrow(), 7);
     /// ```
     ///
     /// An example of panic:
diff --git a/src/libcore/iter.rs b/src/libcore/iter.rs
index e3e783329ec..ddc4fb32cde 100644
--- a/src/libcore/iter.rs
+++ b/src/libcore/iter.rs
@@ -2740,7 +2740,13 @@ pub trait Extend<A> {
 /// It is important to note that both back and forth work on the same range,
 /// and do not cross: iteration is over when they meet in the middle.
 ///
+/// In a similar fashion to the [`Iterator`] protocol, once a
+/// `DoubleEndedIterator` returns `None` from a `next_back()`, calling it again
+/// may or may not ever return `Some` again. `next()` and `next_back()` are
+/// interchangable for this purpose.
+///
 /// [`Iterator`]: trait.Iterator.html
+///
 /// # Examples
 ///
 /// Basic usage: