Compare sample code output to that of the library function.

Author: nk9

library/alloc/src/vec/mod.rs

@@ -3668,19 +3668,25 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     /// # let some_predicate = |x: &mut i32| { *x % 2 == 1 };
     /// # let mut vec = vec![0, 1, 2, 3, 4, 5, 6];
+    /// # let mut vec2 = vec.clone();
     /// # let range = 1..5;
     /// let mut i = range.start;
     /// let end_items = vec.len() - range.end;
+    /// let mut extracted = vec![];
+    ///
     /// while i < vec.len() - end_items {
     ///     if some_predicate(&mut vec[i]) {
     ///         let val = vec.remove(i);
+    ///         extracted.push(val);
     ///         // your code here
     ///     } else {
     ///         i += 1;
     ///     }
     /// }
     ///
-    /// # assert_eq!(vec, vec![0, 2, 4, 5, 6]);
+    /// # let extracted2: Vec<_> = vec2.extract_if(range, some_predicate).collect();
+    /// # assert_eq!(vec, vec2);
+    /// # assert_eq!(extracted, extracted2);
     /// ```
     ///
     /// But `extract_if` is easier to use. `extract_if` is also more efficient,