docs(core): update find() and rfind() examples

library/core/src/iter/traits/double_ended.rs

@@ -334,8 +334,18 @@ pub trait DoubleEndedIterator: Iterator {
     /// ```
     /// let a = [1, 2, 3];
     ///
-    /// assert_eq!(a.iter().rfind(|&&x| x == 2), Some(&2));
+    /// assert_eq!(a.into_iter().rfind(|&x| x == 2), Some(2));
+    /// assert_eq!(a.into_iter().rfind(|&x| x == 5), None);
+    /// ```
     ///
+    /// Iterating over references:
+    ///
+    /// ```
+    /// let a = [1, 2, 3];
+    ///
+    /// // `iter()` yields references i.e. `&i32` and `rfind()` takes a
+    /// // reference to each element.
+    /// assert_eq!(a.iter().rfind(|&&x| x == 2), Some(&2));
     /// assert_eq!(a.iter().rfind(|&&x| x == 5), None);
     /// ```
     ///

library/core/src/iter/traits/iterator.rs

@@ -2858,6 +2858,17 @@ pub trait Iterator {
     /// assert_eq!(a.into_iter().find(|&x| x == 5), None);
     /// ```
     ///
+    /// Iterating over references:
+    ///
+    /// ```
+    /// let a = [1, 2, 3];
+    ///
+    /// // `iter()` yields references i.e. `&i32` and `find()` takes a
+    /// // reference to each element.
+    /// assert_eq!(a.iter().find(|&&x| x == 2), Some(&2));
+    /// assert_eq!(a.iter().find(|&&x| x == 5), None);
+    /// ```
+    ///
     /// Stopping at the first `true`:
     ///
     /// ```