Override Iterator methods for vec::IntoIter

Author: sinkuu

src/libcollections/vec.rs

@@ -1777,6 +1777,41 @@ impl<T> Iterator for IntoIter<T> {
         let exact = diff / (if size == 0 {1} else {size});
         (exact, Some(exact))
     }
+
+    #[inline]
+    fn count(self) -> usize {
+        self.size_hint().0
+    }
+
+    #[inline]
+    fn last(self) -> Option<T> {
+        if self.ptr == self.end {
+            None
+        } else {
+            unsafe {
+                if mem::size_of::<T>() == 0 {
+                    Some(ptr::read(EMPTY as *mut T))
+                } else {
+                    Some(ptr::read(self.end.offset(-1)))
+                }
+            }
+        }
+    }
+
+    #[inline]
+    fn nth(&mut self, n: usize) -> Option<T> {
+        let size = mem::size_of::<T>();
+        let p = unsafe {
+            mem::transmute(self.ptr as usize + if size == 0 { 1 } else { size } * n)
+        };
+        if p >= self.end {
+            self.ptr = self.end;
+            None
+        } else {
+            self.ptr = p;
+            self.next()
+        }
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]

src/libcollectionstest/vec.rs

@@ -542,6 +542,18 @@ fn test_split_off() {
     assert_eq!(vec2, [5, 6]);
 }
 
+#[test]
+fn test_into_iter() {
+    let mut it = vec![1, 2, 3, 4, 5, 6].into_iter();
+    assert_eq!(it.nth(2), Some(3));
+    assert_eq!(it.next(), Some(4));
+    assert_eq!(it.nth(2), None);
+    assert_eq!(it.next(), None);
+
+    assert_eq!(vec![1, 2, 3].into_iter().last(), Some(3));
+    assert_eq!(vec![1, 2, 3].into_iter().count(), 3);
+}
+
 #[bench]
 fn bench_new(b: &mut Bencher) {
     b.iter(|| {