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-rw-r--r--library/alloc/src/borrow.rs6
-rw-r--r--library/alloc/src/collections/binary_heap.rs3
-rw-r--r--library/alloc/src/collections/binary_heap/tests.rs489
-rw-r--r--library/alloc/src/collections/linked_list.rs10
-rw-r--r--library/alloc/src/collections/linked_list/tests.rs695
-rw-r--r--library/alloc/src/collections/vec_deque/mod.rs43
-rw-r--r--library/alloc/src/collections/vec_deque/spec_extend.rs73
-rw-r--r--library/alloc/src/collections/vec_deque/tests.rs294
-rw-r--r--library/alloc/src/rc.rs19
-rw-r--r--library/alloc/src/sync.rs19
-rw-r--r--library/alloc/src/vec/into_iter.rs5
-rw-r--r--library/alloc/src/vec/is_zero.rs9
-rw-r--r--library/alloc/src/vec/mod.rs42
-rw-r--r--library/alloc/src/vec/spec_extend.rs2
14 files changed, 1627 insertions, 82 deletions
diff --git a/library/alloc/src/borrow.rs b/library/alloc/src/borrow.rs
index 8b13e36c4b3..cb4e438f8be 100644
--- a/library/alloc/src/borrow.rs
+++ b/library/alloc/src/borrow.rs
@@ -292,8 +292,7 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
     ///
     /// # Examples
     ///
-    /// Calling `into_owned` on a `Cow::Borrowed` clones the underlying data
-    /// and becomes a `Cow::Owned`:
+    /// Calling `into_owned` on a `Cow::Borrowed` returns a clone of the borrowed data:
     ///
     /// ```
     /// use std::borrow::Cow;
@@ -307,7 +306,8 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
     /// );
     /// ```
     ///
-    /// Calling `into_owned` on a `Cow::Owned` is a no-op:
+    /// Calling `into_owned` on a `Cow::Owned` returns the owned data. The data is moved out of the
+    /// `Cow` without being cloned.
     ///
     /// ```
     /// use std::borrow::Cow;
diff --git a/library/alloc/src/collections/binary_heap.rs b/library/alloc/src/collections/binary_heap.rs
index ef5bef0253a..c3c1d0c92a8 100644
--- a/library/alloc/src/collections/binary_heap.rs
+++ b/library/alloc/src/collections/binary_heap.rs
@@ -155,6 +155,9 @@ use crate::vec::{self, AsVecIntoIter, Vec};
 
 use super::SpecExtend;
 
+#[cfg(test)]
+mod tests;
+
 /// A priority queue implemented with a binary heap.
 ///
 /// This will be a max-heap.
diff --git a/library/alloc/src/collections/binary_heap/tests.rs b/library/alloc/src/collections/binary_heap/tests.rs
new file mode 100644
index 00000000000..7c758dbb3ab
--- /dev/null
+++ b/library/alloc/src/collections/binary_heap/tests.rs
@@ -0,0 +1,489 @@
+use super::*;
+use crate::boxed::Box;
+use std::iter::TrustedLen;
+use std::panic::{catch_unwind, AssertUnwindSafe};
+use std::sync::atomic::{AtomicU32, Ordering};
+
+#[test]
+fn test_iterator() {
+    let data = vec![5, 9, 3];
+    let iterout = [9, 5, 3];
+    let heap = BinaryHeap::from(data);
+    let mut i = 0;
+    for el in &heap {
+        assert_eq!(*el, iterout[i]);
+        i += 1;
+    }
+}
+
+#[test]
+fn test_iter_rev_cloned_collect() {
+    let data = vec![5, 9, 3];
+    let iterout = vec![3, 5, 9];
+    let pq = BinaryHeap::from(data);
+
+    let v: Vec<_> = pq.iter().rev().cloned().collect();
+    assert_eq!(v, iterout);
+}
+
+#[test]
+fn test_into_iter_collect() {
+    let data = vec![5, 9, 3];
+    let iterout = vec![9, 5, 3];
+    let pq = BinaryHeap::from(data);
+
+    let v: Vec<_> = pq.into_iter().collect();
+    assert_eq!(v, iterout);
+}
+
+#[test]
+fn test_into_iter_size_hint() {
+    let data = vec![5, 9];
+    let pq = BinaryHeap::from(data);
+
+    let mut it = pq.into_iter();
+
+    assert_eq!(it.size_hint(), (2, Some(2)));
+    assert_eq!(it.next(), Some(9));
+
+    assert_eq!(it.size_hint(), (1, Some(1)));
+    assert_eq!(it.next(), Some(5));
+
+    assert_eq!(it.size_hint(), (0, Some(0)));
+    assert_eq!(it.next(), None);
+}
+
+#[test]
+fn test_into_iter_rev_collect() {
+    let data = vec![5, 9, 3];
+    let iterout = vec![3, 5, 9];
+    let pq = BinaryHeap::from(data);
+
+    let v: Vec<_> = pq.into_iter().rev().collect();
+    assert_eq!(v, iterout);
+}
+
+#[test]
+fn test_into_iter_sorted_collect() {
+    let heap = BinaryHeap::from(vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1]);
+    let it = heap.into_iter_sorted();
+    let sorted = it.collect::<Vec<_>>();
+    assert_eq!(sorted, vec![10, 9, 8, 7, 6, 5, 4, 3, 2, 2, 1, 1, 0]);
+}
+
+#[test]
+fn test_drain_sorted_collect() {
+    let mut heap = BinaryHeap::from(vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1]);
+    let it = heap.drain_sorted();
+    let sorted = it.collect::<Vec<_>>();
+    assert_eq!(sorted, vec![10, 9, 8, 7, 6, 5, 4, 3, 2, 2, 1, 1, 0]);
+}
+
+fn check_exact_size_iterator<I: ExactSizeIterator>(len: usize, it: I) {
+    let mut it = it;
+
+    for i in 0..it.len() {
+        let (lower, upper) = it.size_hint();
+        assert_eq!(Some(lower), upper);
+        assert_eq!(lower, len - i);
+        assert_eq!(it.len(), len - i);
+        it.next();
+    }
+    assert_eq!(it.len(), 0);
+    assert!(it.is_empty());
+}
+
+#[test]
+fn test_exact_size_iterator() {
+    let heap = BinaryHeap::from(vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1]);
+    check_exact_size_iterator(heap.len(), heap.iter());
+    check_exact_size_iterator(heap.len(), heap.clone().into_iter());
+    check_exact_size_iterator(heap.len(), heap.clone().into_iter_sorted());
+    check_exact_size_iterator(heap.len(), heap.clone().drain());
+    check_exact_size_iterator(heap.len(), heap.clone().drain_sorted());
+}
+
+fn check_trusted_len<I: TrustedLen>(len: usize, it: I) {
+    let mut it = it;
+    for i in 0..len {
+        let (lower, upper) = it.size_hint();
+        if upper.is_some() {
+            assert_eq!(Some(lower), upper);
+            assert_eq!(lower, len - i);
+        }
+        it.next();
+    }
+}
+
+#[test]
+fn test_trusted_len() {
+    let heap = BinaryHeap::from(vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1]);
+    check_trusted_len(heap.len(), heap.clone().into_iter_sorted());
+    check_trusted_len(heap.len(), heap.clone().drain_sorted());
+}
+
+#[test]
+fn test_peek_and_pop() {
+    let data = vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
+    let mut sorted = data.clone();
+    sorted.sort();
+    let mut heap = BinaryHeap::from(data);
+    while !heap.is_empty() {
+        assert_eq!(heap.peek().unwrap(), sorted.last().unwrap());
+        assert_eq!(heap.pop().unwrap(), sorted.pop().unwrap());
+    }
+}
+
+#[test]
+fn test_peek_mut() {
+    let data = vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
+    let mut heap = BinaryHeap::from(data);
+    assert_eq!(heap.peek(), Some(&10));
+    {
+        let mut top = heap.peek_mut().unwrap();
+        *top -= 2;
+    }
+    assert_eq!(heap.peek(), Some(&9));
+}
+
+#[test]
+fn test_peek_mut_pop() {
+    let data = vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1];
+    let mut heap = BinaryHeap::from(data);
+    assert_eq!(heap.peek(), Some(&10));
+    {
+        let mut top = heap.peek_mut().unwrap();
+        *top -= 2;
+        assert_eq!(PeekMut::pop(top), 8);
+    }
+    assert_eq!(heap.peek(), Some(&9));
+}
+
+#[test]
+fn test_push() {
+    let mut heap = BinaryHeap::from(vec![2, 4, 9]);
+    assert_eq!(heap.len(), 3);
+    assert!(*heap.peek().unwrap() == 9);
+    heap.push(11);
+    assert_eq!(heap.len(), 4);
+    assert!(*heap.peek().unwrap() == 11);
+    heap.push(5);
+    assert_eq!(heap.len(), 5);
+    assert!(*heap.peek().unwrap() == 11);
+    heap.push(27);
+    assert_eq!(heap.len(), 6);
+    assert!(*heap.peek().unwrap() == 27);
+    heap.push(3);
+    assert_eq!(heap.len(), 7);
+    assert!(*heap.peek().unwrap() == 27);
+    heap.push(103);
+    assert_eq!(heap.len(), 8);
+    assert!(*heap.peek().unwrap() == 103);
+}
+
+#[test]
+fn test_push_unique() {
+    let mut heap = BinaryHeap::<Box<_>>::from(vec![box 2, box 4, box 9]);
+    assert_eq!(heap.len(), 3);
+    assert!(**heap.peek().unwrap() == 9);
+    heap.push(box 11);
+    assert_eq!(heap.len(), 4);
+    assert!(**heap.peek().unwrap() == 11);
+    heap.push(box 5);
+    assert_eq!(heap.len(), 5);
+    assert!(**heap.peek().unwrap() == 11);
+    heap.push(box 27);
+    assert_eq!(heap.len(), 6);
+    assert!(**heap.peek().unwrap() == 27);
+    heap.push(box 3);
+    assert_eq!(heap.len(), 7);
+    assert!(**heap.peek().unwrap() == 27);
+    heap.push(box 103);
+    assert_eq!(heap.len(), 8);
+    assert!(**heap.peek().unwrap() == 103);
+}
+
+fn check_to_vec(mut data: Vec<i32>) {
+    let heap = BinaryHeap::from(data.clone());
+    let mut v = heap.clone().into_vec();
+    v.sort();
+    data.sort();
+
+    assert_eq!(v, data);
+    assert_eq!(heap.into_sorted_vec(), data);
+}
+
+#[test]
+fn test_to_vec() {
+    check_to_vec(vec![]);
+    check_to_vec(vec![5]);
+    check_to_vec(vec![3, 2]);
+    check_to_vec(vec![2, 3]);
+    check_to_vec(vec![5, 1, 2]);
+    check_to_vec(vec![1, 100, 2, 3]);
+    check_to_vec(vec![1, 3, 5, 7, 9, 2, 4, 6, 8, 0]);
+    check_to_vec(vec![2, 4, 6, 2, 1, 8, 10, 3, 5, 7, 0, 9, 1]);
+    check_to_vec(vec![9, 11, 9, 9, 9, 9, 11, 2, 3, 4, 11, 9, 0, 0, 0, 0]);
+    check_to_vec(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    check_to_vec(vec![10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]);
+    check_to_vec(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 1, 2]);
+    check_to_vec(vec![5, 4, 3, 2, 1, 5, 4, 3, 2, 1, 5, 4, 3, 2, 1]);
+}
+
+#[test]
+fn test_in_place_iterator_specialization() {
+    let src: Vec<usize> = vec![1, 2, 3];
+    let src_ptr = src.as_ptr();
+    let heap: BinaryHeap<_> = src.into_iter().map(std::convert::identity).collect();
+    let heap_ptr = heap.iter().next().unwrap() as *const usize;
+    assert_eq!(src_ptr, heap_ptr);
+    let sink: Vec<_> = heap.into_iter().map(std::convert::identity).collect();
+    let sink_ptr = sink.as_ptr();
+    assert_eq!(heap_ptr, sink_ptr);
+}
+
+#[test]
+fn test_empty_pop() {
+    let mut heap = BinaryHeap::<i32>::new();
+    assert!(heap.pop().is_none());
+}
+
+#[test]
+fn test_empty_peek() {
+    let empty = BinaryHeap::<i32>::new();
+    assert!(empty.peek().is_none());
+}
+
+#[test]
+fn test_empty_peek_mut() {
+    let mut empty = BinaryHeap::<i32>::new();
+    assert!(empty.peek_mut().is_none());
+}
+
+#[test]
+fn test_from_iter() {
+    let xs = vec![9, 8, 7, 6, 5, 4, 3, 2, 1];
+
+    let mut q: BinaryHeap<_> = xs.iter().rev().cloned().collect();
+
+    for &x in &xs {
+        assert_eq!(q.pop().unwrap(), x);
+    }
+}
+
+#[test]
+fn test_drain() {
+    let mut q: BinaryHeap<_> = [9, 8, 7, 6, 5, 4, 3, 2, 1].iter().cloned().collect();
+
+    assert_eq!(q.drain().take(5).count(), 5);
+
+    assert!(q.is_empty());
+}
+
+#[test]
+fn test_drain_sorted() {
+    let mut q: BinaryHeap<_> = [9, 8, 7, 6, 5, 4, 3, 2, 1].iter().cloned().collect();
+
+    assert_eq!(q.drain_sorted().take(5).collect::<Vec<_>>(), vec![9, 8, 7, 6, 5]);
+
+    assert!(q.is_empty());
+}
+
+#[test]
+fn test_drain_sorted_leak() {
+    static DROPS: AtomicU32 = AtomicU32::new(0);
+
+    #[derive(Clone, PartialEq, Eq, PartialOrd, Ord)]
+    struct D(u32, bool);
+
+    impl Drop for D {
+        fn drop(&mut self) {
+            DROPS.fetch_add(1, Ordering::SeqCst);
+
+            if self.1 {
+                panic!("panic in `drop`");
+            }
+        }
+    }
+
+    let mut q = BinaryHeap::from(vec![
+        D(0, false),
+        D(1, false),
+        D(2, false),
+        D(3, true),
+        D(4, false),
+        D(5, false),
+    ]);
+
+    catch_unwind(AssertUnwindSafe(|| drop(q.drain_sorted()))).ok();
+
+    assert_eq!(DROPS.load(Ordering::SeqCst), 6);
+}
+
+#[test]
+fn test_extend_ref() {
+    let mut a = BinaryHeap::new();
+    a.push(1);
+    a.push(2);
+
+    a.extend(&[3, 4, 5]);
+
+    assert_eq!(a.len(), 5);
+    assert_eq!(a.into_sorted_vec(), [1, 2, 3, 4, 5]);
+
+    let mut a = BinaryHeap::new();
+    a.push(1);
+    a.push(2);
+    let mut b = BinaryHeap::new();
+    b.push(3);
+    b.push(4);
+    b.push(5);
+
+    a.extend(&b);
+
+    assert_eq!(a.len(), 5);
+    assert_eq!(a.into_sorted_vec(), [1, 2, 3, 4, 5]);
+}
+
+#[test]
+fn test_append() {
+    let mut a = BinaryHeap::from(vec![-10, 1, 2, 3, 3]);
+    let mut b = BinaryHeap::from(vec![-20, 5, 43]);
+
+    a.append(&mut b);
+
+    assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
+    assert!(b.is_empty());
+}
+
+#[test]
+fn test_append_to_empty() {
+    let mut a = BinaryHeap::new();
+    let mut b = BinaryHeap::from(vec![-20, 5, 43]);
+
+    a.append(&mut b);
+
+    assert_eq!(a.into_sorted_vec(), [-20, 5, 43]);
+    assert!(b.is_empty());
+}
+
+#[test]
+fn test_extend_specialization() {
+    let mut a = BinaryHeap::from(vec![-10, 1, 2, 3, 3]);
+    let b = BinaryHeap::from(vec![-20, 5, 43]);
+
+    a.extend(b);
+
+    assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
+}
+
+#[allow(dead_code)]
+fn assert_covariance() {
+    fn drain<'new>(d: Drain<'static, &'static str>) -> Drain<'new, &'new str> {
+        d
+    }
+}
+
+#[test]
+fn test_retain() {
+    let mut a = BinaryHeap::from(vec![100, 10, 50, 1, 2, 20, 30]);
+    a.retain(|&x| x != 2);
+
+    // Check that 20 moved into 10's place.
+    assert_eq!(a.clone().into_vec(), [100, 20, 50, 1, 10, 30]);
+
+    a.retain(|_| true);
+
+    assert_eq!(a.clone().into_vec(), [100, 20, 50, 1, 10, 30]);
+
+    a.retain(|&x| x < 50);
+
+    assert_eq!(a.clone().into_vec(), [30, 20, 10, 1]);
+
+    a.retain(|_| false);
+
+    assert!(a.is_empty());
+}
+
+// old binaryheap failed this test
+//
+// Integrity means that all elements are present after a comparison panics,
+// even if the order might not be correct.
+//
+// Destructors must be called exactly once per element.
+// FIXME: re-enable emscripten once it can unwind again
+#[test]
+#[cfg(not(target_os = "emscripten"))]
+fn panic_safe() {
+    use rand::{seq::SliceRandom, thread_rng};
+    use std::cmp;
+    use std::panic::{self, AssertUnwindSafe};
+    use std::sync::atomic::{AtomicUsize, Ordering};
+
+    static DROP_COUNTER: AtomicUsize = AtomicUsize::new(0);
+
+    #[derive(Eq, PartialEq, Ord, Clone, Debug)]
+    struct PanicOrd<T>(T, bool);
+
+    impl<T> Drop for PanicOrd<T> {
+        fn drop(&mut self) {
+            // update global drop count
+            DROP_COUNTER.fetch_add(1, Ordering::SeqCst);
+        }
+    }
+
+    impl<T: PartialOrd> PartialOrd for PanicOrd<T> {
+        fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+            if self.1 || other.1 {
+                panic!("Panicking comparison");
+            }
+            self.0.partial_cmp(&other.0)
+        }
+    }
+    let mut rng = thread_rng();
+    const DATASZ: usize = 32;
+    // Miri is too slow
+    let ntest = if cfg!(miri) { 1 } else { 10 };
+
+    // don't use 0 in the data -- we want to catch the zeroed-out case.
+    let data = (1..=DATASZ).collect::<Vec<_>>();
+
+    // since it's a fuzzy test, run several tries.
+    for _ in 0..ntest {
+        for i in 1..=DATASZ {
+            DROP_COUNTER.store(0, Ordering::SeqCst);
+
+            let mut panic_ords: Vec<_> =
+                data.iter().filter(|&&x| x != i).map(|&x| PanicOrd(x, false)).collect();
+            let panic_item = PanicOrd(i, true);
+
+            // heapify the sane items
+            panic_ords.shuffle(&mut rng);
+            let mut heap = BinaryHeap::from(panic_ords);
+            let inner_data;
+
+            {
+                // push the panicking item to the heap and catch the panic
+                let thread_result = {
+                    let mut heap_ref = AssertUnwindSafe(&mut heap);
+                    panic::catch_unwind(move || {
+                        heap_ref.push(panic_item);
+                    })
+                };
+                assert!(thread_result.is_err());
+
+                // Assert no elements were dropped
+                let drops = DROP_COUNTER.load(Ordering::SeqCst);
+                assert!(drops == 0, "Must not drop items. drops={}", drops);
+                inner_data = heap.clone().into_vec();
+                drop(heap);
+            }
+            let drops = DROP_COUNTER.load(Ordering::SeqCst);
+            assert_eq!(drops, DATASZ);
+
+            let mut data_sorted = inner_data.into_iter().map(|p| p.0).collect::<Vec<_>>();
+            data_sorted.sort();
+            assert_eq!(data_sorted, data);
+        }
+    }
+}
diff --git a/library/alloc/src/collections/linked_list.rs b/library/alloc/src/collections/linked_list.rs
index d81f24e7202..736b38370ab 100644
--- a/library/alloc/src/collections/linked_list.rs
+++ b/library/alloc/src/collections/linked_list.rs
@@ -645,7 +645,7 @@ impl<T> LinkedList<T> {
     /// Returns `true` if the `LinkedList` contains an element equal to the
     /// given value.
     ///
-    /// This operation should compute in *O*(*n*) time.
+    /// This operation should compute linearly in *O*(*n*) time.
     ///
     /// # Examples
     ///
@@ -1569,7 +1569,7 @@ impl<'a, T> CursorMut<'a, T> {
     /// Appends an element to the front of the cursor's parent list. The node
     /// that the cursor points to is unchanged, even if it is the "ghost" node.
     ///
-    /// This operation should compute in O(1) time.
+    /// This operation should compute in *O*(1) time.
     // `push_front` continues to point to "ghost" when it addes a node to mimic
     // the behavior of `insert_before` on an empty list.
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
@@ -1584,7 +1584,7 @@ impl<'a, T> CursorMut<'a, T> {
     /// Appends an element to the back of the cursor's parent list. The node
     /// that the cursor points to is unchanged, even if it is the "ghost" node.
     ///
-    /// This operation should compute in O(1) time.
+    /// This operation should compute in *O*(1) time.
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
     pub fn push_back(&mut self, elt: T) {
         // Safety: We know that `push_back` does not change the position in
@@ -1603,7 +1603,7 @@ impl<'a, T> CursorMut<'a, T> {
     /// unchanged, unless it was pointing to the front element. In that case, it
     /// points to the new front element.
     ///
-    /// This operation should compute in O(1) time.
+    /// This operation should compute in *O*(1) time.
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
     pub fn pop_front(&mut self) -> Option<T> {
         // We can't check if current is empty, we must check the list directly.
@@ -1630,7 +1630,7 @@ impl<'a, T> CursorMut<'a, T> {
     /// unchanged, unless it was pointing to the back element. In that case, it
     /// points to the "ghost" element.
     ///
-    /// This operation should compute in O(1) time.
+    /// This operation should compute in *O*(1) time.
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
     pub fn pop_back(&mut self) -> Option<T> {
         if self.list.is_empty() {
diff --git a/library/alloc/src/collections/linked_list/tests.rs b/library/alloc/src/collections/linked_list/tests.rs
index 5a65ed7a962..38c702aa387 100644
--- a/library/alloc/src/collections/linked_list/tests.rs
+++ b/library/alloc/src/collections/linked_list/tests.rs
@@ -1,10 +1,55 @@
 use super::*;
+use crate::vec::Vec;
 
+use std::panic::{catch_unwind, AssertUnwindSafe};
 use std::thread;
-use std::vec::Vec;
 
 use rand::{thread_rng, RngCore};
 
+#[test]
+fn test_basic() {
+    let mut m = LinkedList::<Box<_>>::new();
+    assert_eq!(m.pop_front(), None);
+    assert_eq!(m.pop_back(), None);
+    assert_eq!(m.pop_front(), None);
+    m.push_front(box 1);
+    assert_eq!(m.pop_front(), Some(box 1));
+    m.push_back(box 2);
+    m.push_back(box 3);
+    assert_eq!(m.len(), 2);
+    assert_eq!(m.pop_front(), Some(box 2));
+    assert_eq!(m.pop_front(), Some(box 3));
+    assert_eq!(m.len(), 0);
+    assert_eq!(m.pop_front(), None);
+    m.push_back(box 1);
+    m.push_back(box 3);
+    m.push_back(box 5);
+    m.push_back(box 7);
+    assert_eq!(m.pop_front(), Some(box 1));
+
+    let mut n = LinkedList::new();
+    n.push_front(2);
+    n.push_front(3);
+    {
+        assert_eq!(n.front().unwrap(), &3);
+        let x = n.front_mut().unwrap();
+        assert_eq!(*x, 3);
+        *x = 0;
+    }
+    {
+        assert_eq!(n.back().unwrap(), &2);
+        let y = n.back_mut().unwrap();
+        assert_eq!(*y, 2);
+        *y = 1;
+    }
+    assert_eq!(n.pop_front(), Some(0));
+    assert_eq!(n.pop_front(), Some(1));
+}
+
+fn generate_test() -> LinkedList<i32> {
+    list_from(&[0, 1, 2, 3, 4, 5, 6])
+}
+
 fn list_from<T: Clone>(v: &[T]) -> LinkedList<T> {
     v.iter().cloned().collect()
 }
@@ -111,6 +156,123 @@ fn test_append() {
 }
 
 #[test]
+fn test_iterator() {
+    let m = generate_test();
+    for (i, elt) in m.iter().enumerate() {
+        assert_eq!(i as i32, *elt);
+    }
+    let mut n = LinkedList::new();
+    assert_eq!(n.iter().next(), None);
+    n.push_front(4);
+    let mut it = n.iter();
+    assert_eq!(it.size_hint(), (1, Some(1)));
+    assert_eq!(it.next().unwrap(), &4);
+    assert_eq!(it.size_hint(), (0, Some(0)));
+    assert_eq!(it.next(), None);
+}
+
+#[test]
+fn test_iterator_clone() {
+    let mut n = LinkedList::new();
+    n.push_back(2);
+    n.push_back(3);
+    n.push_back(4);
+    let mut it = n.iter();
+    it.next();
+    let mut jt = it.clone();
+    assert_eq!(it.next(), jt.next());
+    assert_eq!(it.next_back(), jt.next_back());
+    assert_eq!(it.next(), jt.next());
+}
+
+#[test]
+fn test_iterator_double_end() {
+    let mut n = LinkedList::new();
+    assert_eq!(n.iter().next(), None);
+    n.push_front(4);
+    n.push_front(5);
+    n.push_front(6);
+    let mut it = n.iter();
+    assert_eq!(it.size_hint(), (3, Some(3)));
+    assert_eq!(it.next().unwrap(), &6);
+    assert_eq!(it.size_hint(), (2, Some(2)));
+    assert_eq!(it.next_back().unwrap(), &4);
+    assert_eq!(it.size_hint(), (1, Some(1)));
+    assert_eq!(it.next_back().unwrap(), &5);
+    assert_eq!(it.next_back(), None);
+    assert_eq!(it.next(), None);
+}
+
+#[test]
+fn test_rev_iter() {
+    let m = generate_test();
+    for (i, elt) in m.iter().rev().enumerate() {
+        assert_eq!((6 - i) as i32, *elt);
+    }
+    let mut n = LinkedList::new();
+    assert_eq!(n.iter().rev().next(), None);
+    n.push_front(4);
+    let mut it = n.iter().rev();
+    assert_eq!(it.size_hint(), (1, Some(1)));
+    assert_eq!(it.next().unwrap(), &4);
+    assert_eq!(it.size_hint(), (0, Some(0)));
+    assert_eq!(it.next(), None);
+}
+
+#[test]
+fn test_mut_iter() {
+    let mut m = generate_test();
+    let mut len = m.len();
+    for (i, elt) in m.iter_mut().enumerate() {
+        assert_eq!(i as i32, *elt);
+        len -= 1;
+    }
+    assert_eq!(len, 0);
+    let mut n = LinkedList::new();
+    assert!(n.iter_mut().next().is_none());
+    n.push_front(4);
+    n.push_back(5);
+    let mut it = n.iter_mut();
+    assert_eq!(it.size_hint(), (2, Some(2)));
+    assert!(it.next().is_some());
+    assert!(it.next().is_some());
+    assert_eq!(it.size_hint(), (0, Some(0)));
+    assert!(it.next().is_none());
+}
+
+#[test]
+fn test_iterator_mut_double_end() {
+    let mut n = LinkedList::new();
+    assert!(n.iter_mut().next_back().is_none());
+    n.push_front(4);
+    n.push_front(5);
+    n.push_front(6);
+    let mut it = n.iter_mut();
+    assert_eq!(it.size_hint(), (3, Some(3)));
+    assert_eq!(*it.next().unwrap(), 6);
+    assert_eq!(it.size_hint(), (2, Some(2)));
+    assert_eq!(*it.next_back().unwrap(), 4);
+    assert_eq!(it.size_hint(), (1, Some(1)));
+    assert_eq!(*it.next_back().unwrap(), 5);
+    assert!(it.next_back().is_none());
+    assert!(it.next().is_none());
+}
+
+#[test]
+fn test_mut_rev_iter() {
+    let mut m = generate_test();
+    for (i, elt) in m.iter_mut().rev().enumerate() {
+        assert_eq!((6 - i) as i32, *elt);
+    }
+    let mut n = LinkedList::new();
+    assert!(n.iter_mut().rev().next().is_none());
+    n.push_front(4);
+    let mut it = n.iter_mut().rev();
+    assert!(it.next().is_some());
+    assert!(it.next().is_none());
+}
+
+#[test]
 fn test_clone_from() {
     // Short cloned from long
     {
@@ -168,13 +330,60 @@ fn test_send() {
 }
 
 #[test]
-fn test_fuzz() {
-    for _ in 0..25 {
-        fuzz_test(3);
-        fuzz_test(16);
-        #[cfg(not(miri))] // Miri is too slow
-        fuzz_test(189);
-    }
+fn test_eq() {
+    let mut n = list_from(&[]);
+    let mut m = list_from(&[]);
+    assert!(n == m);
+    n.push_front(1);
+    assert!(n != m);
+    m.push_back(1);
+    assert!(n == m);
+
+    let n = list_from(&[2, 3, 4]);
+    let m = list_from(&[1, 2, 3]);
+    assert!(n != m);
+}
+
+#[test]
+fn test_ord() {
+    let n = list_from(&[]);
+    let m = list_from(&[1, 2, 3]);
+    assert!(n < m);
+    assert!(m > n);
+    assert!(n <= n);
+    assert!(n >= n);
+}
+
+#[test]
+fn test_ord_nan() {
+    let nan = 0.0f64 / 0.0;
+    let n = list_from(&[nan]);
+    let m = list_from(&[nan]);
+    assert!(!(n < m));
+    assert!(!(n > m));
+    assert!(!(n <= m));
+    assert!(!(n >= m));
+
+    let n = list_from(&[nan]);
+    let one = list_from(&[1.0f64]);
+    assert!(!(n < one));
+    assert!(!(n > one));
+    assert!(!(n <= one));
+    assert!(!(n >= one));
+
+    let u = list_from(&[1.0f64, 2.0, nan]);
+    let v = list_from(&[1.0f64, 2.0, 3.0]);
+    assert!(!(u < v));
+    assert!(!(u > v));
+    assert!(!(u <= v));
+    assert!(!(u >= v));
+
+    let s = list_from(&[1.0f64, 2.0, 4.0, 2.0]);
+    let t = list_from(&[1.0f64, 2.0, 3.0, 2.0]);
+    assert!(!(s < t));
+    assert!(s > one);
+    assert!(!(s <= one));
+    assert!(s >= one);
 }
 
 #[test]
@@ -215,6 +424,62 @@ fn test_split_off() {
     }
 }
 
+#[test]
+fn test_split_off_2() {
+    // singleton
+    {
+        let mut m = LinkedList::new();
+        m.push_back(1);
+
+        let p = m.split_off(0);
+        assert_eq!(m.len(), 0);
+        assert_eq!(p.len(), 1);
+        assert_eq!(p.back(), Some(&1));
+        assert_eq!(p.front(), Some(&1));
+    }
+
+    // not singleton, forwards
+    {
+        let u = vec![1, 2, 3, 4, 5];
+        let mut m = list_from(&u);
+        let mut n = m.split_off(2);
+        assert_eq!(m.len(), 2);
+        assert_eq!(n.len(), 3);
+        for elt in 1..3 {
+            assert_eq!(m.pop_front(), Some(elt));
+        }
+        for elt in 3..6 {
+            assert_eq!(n.pop_front(), Some(elt));
+        }
+    }
+    // not singleton, backwards
+    {
+        let u = vec![1, 2, 3, 4, 5];
+        let mut m = list_from(&u);
+        let mut n = m.split_off(4);
+        assert_eq!(m.len(), 4);
+        assert_eq!(n.len(), 1);
+        for elt in 1..5 {
+            assert_eq!(m.pop_front(), Some(elt));
+        }
+        for elt in 5..6 {
+            assert_eq!(n.pop_front(), Some(elt));
+        }
+    }
+
+    // no-op on the last index
+    {
+        let mut m = LinkedList::new();
+        m.push_back(1);
+
+        let p = m.split_off(1);
+        assert_eq!(m.len(), 1);
+        assert_eq!(p.len(), 0);
+        assert_eq!(m.back(), Some(&1));
+        assert_eq!(m.front(), Some(&1));
+    }
+}
+
 fn fuzz_test(sz: i32) {
     let mut m: LinkedList<_> = LinkedList::new();
     let mut v = vec![];
@@ -254,6 +519,25 @@ fn fuzz_test(sz: i32) {
 }
 
 #[test]
+fn test_fuzz() {
+    for _ in 0..25 {
+        fuzz_test(3);
+        fuzz_test(16);
+        #[cfg(not(miri))] // Miri is too slow
+        fuzz_test(189);
+    }
+}
+
+#[test]
+fn test_show() {
+    let list: LinkedList<_> = (0..10).collect();
+    assert_eq!(format!("{list:?}"), "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]");
+
+    let list: LinkedList<_> = ["just", "one", "test", "more"].into_iter().collect();
+    assert_eq!(format!("{list:?}"), "[\"just\", \"one\", \"test\", \"more\"]");
+}
+
+#[test]
 fn drain_filter_test() {
     let mut m: LinkedList<u32> = LinkedList::new();
     m.extend(&[1, 2, 3, 4, 5, 6]);
@@ -475,3 +759,398 @@ fn test_cursor_pop_front_back() {
     assert_eq!(c.current(), None);
     assert_eq!(c.index, 2);
 }
+
+#[test]
+fn test_extend_ref() {
+    let mut a = LinkedList::new();
+    a.push_back(1);
+
+    a.extend(&[2, 3, 4]);
+
+    assert_eq!(a.len(), 4);
+    assert_eq!(a, list_from(&[1, 2, 3, 4]));
+
+    let mut b = LinkedList::new();
+    b.push_back(5);
+    b.push_back(6);
+    a.extend(&b);
+
+    assert_eq!(a.len(), 6);
+    assert_eq!(a, list_from(&[1, 2, 3, 4, 5, 6]));
+}
+
+#[test]
+fn test_extend() {
+    let mut a = LinkedList::new();
+    a.push_back(1);
+    a.extend(vec![2, 3, 4]); // uses iterator
+
+    assert_eq!(a.len(), 4);
+    assert!(a.iter().eq(&[1, 2, 3, 4]));
+
+    let b: LinkedList<_> = [5, 6, 7].into_iter().collect();
+    a.extend(b); // specializes to `append`
+
+    assert_eq!(a.len(), 7);
+    assert!(a.iter().eq(&[1, 2, 3, 4, 5, 6, 7]));
+}
+
+#[test]
+fn test_contains() {
+    let mut l = LinkedList::new();
+    l.extend(&[2, 3, 4]);
+
+    assert!(l.contains(&3));
+    assert!(!l.contains(&1));
+
+    l.clear();
+
+    assert!(!l.contains(&3));
+}
+
+#[test]
+fn drain_filter_empty() {
+    let mut list: LinkedList<i32> = LinkedList::new();
+
+    {
+        let mut iter = list.drain_filter(|_| true);
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+        assert_eq!(iter.next(), None);
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+        assert_eq!(iter.next(), None);
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+    }
+
+    assert_eq!(list.len(), 0);
+    assert_eq!(list.into_iter().collect::<Vec<_>>(), vec![]);
+}
+
+#[test]
+fn drain_filter_zst() {
+    let mut list: LinkedList<_> = [(), (), (), (), ()].into_iter().collect();
+    let initial_len = list.len();
+    let mut count = 0;
+
+    {
+        let mut iter = list.drain_filter(|_| true);
+        assert_eq!(iter.size_hint(), (0, Some(initial_len)));
+        while let Some(_) = iter.next() {
+            count += 1;
+            assert_eq!(iter.size_hint(), (0, Some(initial_len - count)));
+        }
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+        assert_eq!(iter.next(), None);
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+    }
+
+    assert_eq!(count, initial_len);
+    assert_eq!(list.len(), 0);
+    assert_eq!(list.into_iter().collect::<Vec<_>>(), vec![]);
+}
+
+#[test]
+fn drain_filter_false() {
+    let mut list: LinkedList<_> = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].into_iter().collect();
+
+    let initial_len = list.len();
+    let mut count = 0;
+
+    {
+        let mut iter = list.drain_filter(|_| false);
+        assert_eq!(iter.size_hint(), (0, Some(initial_len)));
+        for _ in iter.by_ref() {
+            count += 1;
+        }
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+        assert_eq!(iter.next(), None);
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+    }
+
+    assert_eq!(count, 0);
+    assert_eq!(list.len(), initial_len);
+    assert_eq!(list.into_iter().collect::<Vec<_>>(), vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+}
+
+#[test]
+fn drain_filter_true() {
+    let mut list: LinkedList<_> = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].into_iter().collect();
+
+    let initial_len = list.len();
+    let mut count = 0;
+
+    {
+        let mut iter = list.drain_filter(|_| true);
+        assert_eq!(iter.size_hint(), (0, Some(initial_len)));
+        while let Some(_) = iter.next() {
+            count += 1;
+            assert_eq!(iter.size_hint(), (0, Some(initial_len - count)));
+        }
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+        assert_eq!(iter.next(), None);
+        assert_eq!(iter.size_hint(), (0, Some(0)));
+    }
+
+    assert_eq!(count, initial_len);
+    assert_eq!(list.len(), 0);
+    assert_eq!(list.into_iter().collect::<Vec<_>>(), vec![]);
+}
+
+#[test]
+fn drain_filter_complex() {
+    {
+        //                [+xxx++++++xxxxx++++x+x++]
+        let mut list = [
+            1, 2, 4, 6, 7, 9, 11, 13, 15, 17, 18, 20, 22, 24, 26, 27, 29, 31, 33, 34, 35, 36, 37,
+            39,
+        ]
+        .into_iter()
+        .collect::<LinkedList<_>>();
+
+        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        assert_eq!(removed.len(), 10);
+        assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
+
+        assert_eq!(list.len(), 14);
+        assert_eq!(
+            list.into_iter().collect::<Vec<_>>(),
+            vec![1, 7, 9, 11, 13, 15, 17, 27, 29, 31, 33, 35, 37, 39]
+        );
+    }
+
+    {
+        // [xxx++++++xxxxx++++x+x++]
+        let mut list =
+            [2, 4, 6, 7, 9, 11, 13, 15, 17, 18, 20, 22, 24, 26, 27, 29, 31, 33, 34, 35, 36, 37, 39]
+                .into_iter()
+                .collect::<LinkedList<_>>();
+
+        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        assert_eq!(removed.len(), 10);
+        assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
+
+        assert_eq!(list.len(), 13);
+        assert_eq!(
+            list.into_iter().collect::<Vec<_>>(),
+            vec![7, 9, 11, 13, 15, 17, 27, 29, 31, 33, 35, 37, 39]
+        );
+    }
+
+    {
+        // [xxx++++++xxxxx++++x+x]
+        let mut list =
+            [2, 4, 6, 7, 9, 11, 13, 15, 17, 18, 20, 22, 24, 26, 27, 29, 31, 33, 34, 35, 36]
+                .into_iter()
+                .collect::<LinkedList<_>>();
+
+        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        assert_eq!(removed.len(), 10);
+        assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
+
+        assert_eq!(list.len(), 11);
+        assert_eq!(
+            list.into_iter().collect::<Vec<_>>(),
+            vec![7, 9, 11, 13, 15, 17, 27, 29, 31, 33, 35]
+        );
+    }
+
+    {
+        // [xxxxxxxxxx+++++++++++]
+        let mut list = [2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19]
+            .into_iter()
+            .collect::<LinkedList<_>>();
+
+        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        assert_eq!(removed.len(), 10);
+        assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
+
+        assert_eq!(list.len(), 10);
+        assert_eq!(list.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 7, 9, 11, 13, 15, 17, 19]);
+    }
+
+    {
+        // [+++++++++++xxxxxxxxxx]
+        let mut list = [1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
+            .into_iter()
+            .collect::<LinkedList<_>>();
+
+        let removed = list.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+        assert_eq!(removed.len(), 10);
+        assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
+
+        assert_eq!(list.len(), 10);
+        assert_eq!(list.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 7, 9, 11, 13, 15, 17, 19]);
+    }
+}
+
+#[test]
+fn drain_filter_drop_panic_leak() {
+    static mut DROPS: i32 = 0;
+
+    struct D(bool);
+
+    impl Drop for D {
+        fn drop(&mut self) {
+            unsafe {
+                DROPS += 1;
+            }
+
+            if self.0 {
+                panic!("panic in `drop`");
+            }
+        }
+    }
+
+    let mut q = LinkedList::new();
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_front(D(false));
+    q.push_front(D(true));
+    q.push_front(D(false));
+
+    catch_unwind(AssertUnwindSafe(|| drop(q.drain_filter(|_| true)))).ok();
+
+    assert_eq!(unsafe { DROPS }, 8);
+    assert!(q.is_empty());
+}
+
+#[test]
+fn drain_filter_pred_panic_leak() {
+    static mut DROPS: i32 = 0;
+
+    #[derive(Debug)]
+    struct D(u32);
+
+    impl Drop for D {
+        fn drop(&mut self) {
+            unsafe {
+                DROPS += 1;
+            }
+        }
+    }
+
+    let mut q = LinkedList::new();
+    q.push_back(D(3));
+    q.push_back(D(4));
+    q.push_back(D(5));
+    q.push_back(D(6));
+    q.push_back(D(7));
+    q.push_front(D(2));
+    q.push_front(D(1));
+    q.push_front(D(0));
+
+    catch_unwind(AssertUnwindSafe(|| {
+        drop(q.drain_filter(|item| if item.0 >= 2 { panic!() } else { true }))
+    }))
+    .ok();
+
+    assert_eq!(unsafe { DROPS }, 2); // 0 and 1
+    assert_eq!(q.len(), 6);
+}
+
+#[test]
+fn test_drop() {
+    static mut DROPS: i32 = 0;
+    struct Elem;
+    impl Drop for Elem {
+        fn drop(&mut self) {
+            unsafe {
+                DROPS += 1;
+            }
+        }
+    }
+
+    let mut ring = LinkedList::new();
+    ring.push_back(Elem);
+    ring.push_front(Elem);
+    ring.push_back(Elem);
+    ring.push_front(Elem);
+    drop(ring);
+
+    assert_eq!(unsafe { DROPS }, 4);
+}
+
+#[test]
+fn test_drop_with_pop() {
+    static mut DROPS: i32 = 0;
+    struct Elem;
+    impl Drop for Elem {
+        fn drop(&mut self) {
+            unsafe {
+                DROPS += 1;
+            }
+        }
+    }
+
+    let mut ring = LinkedList::new();
+    ring.push_back(Elem);
+    ring.push_front(Elem);
+    ring.push_back(Elem);
+    ring.push_front(Elem);
+
+    drop(ring.pop_back());
+    drop(ring.pop_front());
+    assert_eq!(unsafe { DROPS }, 2);
+
+    drop(ring);
+    assert_eq!(unsafe { DROPS }, 4);
+}
+
+#[test]
+fn test_drop_clear() {
+    static mut DROPS: i32 = 0;
+    struct Elem;
+    impl Drop for Elem {
+        fn drop(&mut self) {
+            unsafe {
+                DROPS += 1;
+            }
+        }
+    }
+
+    let mut ring = LinkedList::new();
+    ring.push_back(Elem);
+    ring.push_front(Elem);
+    ring.push_back(Elem);
+    ring.push_front(Elem);
+    ring.clear();
+    assert_eq!(unsafe { DROPS }, 4);
+
+    drop(ring);
+    assert_eq!(unsafe { DROPS }, 4);
+}
+
+#[test]
+fn test_drop_panic() {
+    static mut DROPS: i32 = 0;
+
+    struct D(bool);
+
+    impl Drop for D {
+        fn drop(&mut self) {
+            unsafe {
+                DROPS += 1;
+            }
+
+            if self.0 {
+                panic!("panic in `drop`");
+            }
+        }
+    }
+
+    let mut q = LinkedList::new();
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_back(D(false));
+    q.push_front(D(false));
+    q.push_front(D(false));
+    q.push_front(D(true));
+
+    catch_unwind(move || drop(q)).ok();
+
+    assert_eq!(unsafe { DROPS }, 8);
+}
diff --git a/library/alloc/src/collections/vec_deque/mod.rs b/library/alloc/src/collections/vec_deque/mod.rs
index 488671d8d8d..5f1a6848ae6 100644
--- a/library/alloc/src/collections/vec_deque/mod.rs
+++ b/library/alloc/src/collections/vec_deque/mod.rs
@@ -54,6 +54,10 @@ use self::ring_slices::RingSlices;
 
 mod ring_slices;
 
+use self::spec_extend::SpecExtend;
+
+mod spec_extend;
+
 #[cfg(test)]
 mod tests;
 
@@ -1342,6 +1346,12 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// Returns `true` if the deque contains an element equal to the
     /// given value.
     ///
+    /// This operation is *O*(*n*).
+    ///
+    /// Note that if you have a sorted `VecDeque`, [`binary_search`] may be faster.
+    ///
+    /// [`binary_search`]: VecDeque::binary_search
+    ///
     /// # Examples
     ///
     /// ```
@@ -2560,7 +2570,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
         }
     }
 
-    /// Binary searches the sorted deque for a given element.
+    /// Binary searches this `VecDeque` for a given element.
+    /// This behaves similarly to [`contains`] if this `VecDeque` is sorted.
     ///
     /// If the value is found then [`Result::Ok`] is returned, containing the
     /// index of the matching element. If there are multiple matches, then any
@@ -2570,6 +2581,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// See also [`binary_search_by`], [`binary_search_by_key`], and [`partition_point`].
     ///
+    /// [`contains`]: VecDeque::contains
     /// [`binary_search_by`]: VecDeque::binary_search_by
     /// [`binary_search_by_key`]: VecDeque::binary_search_by_key
     /// [`partition_point`]: VecDeque::partition_point
@@ -2614,7 +2626,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
         self.binary_search_by(|e| e.cmp(x))
     }
 
-    /// Binary searches the sorted deque with a comparator function.
+    /// Binary searches this `VecDeque` with a comparator function.
+    /// This behaves similarly to [`contains`] if this `VecDeque` is sorted.
     ///
     /// The comparator function should implement an order consistent
     /// with the sort order of the deque, returning an order code that
@@ -2629,6 +2642,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// See also [`binary_search`], [`binary_search_by_key`], and [`partition_point`].
     ///
+    /// [`contains`]: VecDeque::contains
     /// [`binary_search`]: VecDeque::binary_search
     /// [`binary_search_by_key`]: VecDeque::binary_search_by_key
     /// [`partition_point`]: VecDeque::partition_point
@@ -2667,7 +2681,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
         }
     }
 
-    /// Binary searches the sorted deque with a key extraction function.
+    /// Binary searches this `VecDeque` with a key extraction function.
+    /// This behaves similarly to [`contains`] if this `VecDeque` is sorted.
     ///
     /// Assumes that the deque is sorted by the key, for instance with
     /// [`make_contiguous().sort_by_key()`] using the same key extraction function.
@@ -2680,6 +2695,7 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// See also [`binary_search`], [`binary_search_by`], and [`partition_point`].
     ///
+    /// [`contains`]: VecDeque::contains
     /// [`make_contiguous().sort_by_key()`]: VecDeque::make_contiguous
     /// [`binary_search`]: VecDeque::binary_search
     /// [`binary_search_by`]: VecDeque::binary_search_by
@@ -2958,24 +2974,7 @@ impl<'a, T, A: Allocator> IntoIterator for &'a mut VecDeque<T, A> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, A: Allocator> Extend<T> for VecDeque<T, A> {
     fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
-        // This function should be the moral equivalent of:
-        //
-        //      for item in iter.into_iter() {
-        //          self.push_back(item);
-        //      }
-        let mut iter = iter.into_iter();
-        while let Some(element) = iter.next() {
-            if self.len() == self.capacity() {
-                let (lower, _) = iter.size_hint();
-                self.reserve(lower.saturating_add(1));
-            }
-
-            let head = self.head;
-            self.head = self.wrap_add(self.head, 1);
-            unsafe {
-                self.buffer_write(head, element);
-            }
-        }
+        <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter());
     }
 
     #[inline]
@@ -2992,7 +2991,7 @@ impl<T, A: Allocator> Extend<T> for VecDeque<T, A> {
 #[stable(feature = "extend_ref", since = "1.2.0")]
 impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for VecDeque<T, A> {
     fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
-        self.extend(iter.into_iter().cloned());
+        self.spec_extend(iter.into_iter());
     }
 
     #[inline]
diff --git a/library/alloc/src/collections/vec_deque/spec_extend.rs b/library/alloc/src/collections/vec_deque/spec_extend.rs
new file mode 100644
index 00000000000..172f2e9068f
--- /dev/null
+++ b/library/alloc/src/collections/vec_deque/spec_extend.rs
@@ -0,0 +1,73 @@
+use crate::alloc::Allocator;
+use crate::vec;
+use core::slice;
+
+use super::VecDeque;
+
+// Specialization trait used for VecDeque::extend
+pub(super) trait SpecExtend<T, I> {
+    fn spec_extend(&mut self, iter: I);
+}
+
+impl<T, I, A: Allocator> SpecExtend<T, I> for VecDeque<T, A>
+where
+    I: Iterator<Item = T>,
+{
+    default fn spec_extend(&mut self, mut iter: I) {
+        // This function should be the moral equivalent of:
+        //
+        //      for item in iter {
+        //          self.push_back(item);
+        //      }
+        while let Some(element) = iter.next() {
+            if self.len() == self.capacity() {
+                let (lower, _) = iter.size_hint();
+                self.reserve(lower.saturating_add(1));
+            }
+
+            let head = self.head;
+            self.head = self.wrap_add(self.head, 1);
+            unsafe {
+                self.buffer_write(head, element);
+            }
+        }
+    }
+}
+
+impl<T, A: Allocator> SpecExtend<T, vec::IntoIter<T>> for VecDeque<T, A> {
+    fn spec_extend(&mut self, mut iterator: vec::IntoIter<T>) {
+        let slice = iterator.as_slice();
+        self.reserve(slice.len());
+
+        unsafe {
+            self.copy_slice(self.head, slice);
+            self.head = self.wrap_add(self.head, slice.len());
+        }
+        iterator.forget_remaining_elements();
+    }
+}
+
+impl<'a, T: 'a, I, A: Allocator> SpecExtend<&'a T, I> for VecDeque<T, A>
+where
+    I: Iterator<Item = &'a T>,
+    T: Copy,
+{
+    default fn spec_extend(&mut self, iterator: I) {
+        self.spec_extend(iterator.copied())
+    }
+}
+
+impl<'a, T: 'a, A: Allocator> SpecExtend<&'a T, slice::Iter<'a, T>> for VecDeque<T, A>
+where
+    T: Copy,
+{
+    fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
+        let slice = iterator.as_slice();
+        self.reserve(slice.len());
+
+        unsafe {
+            self.copy_slice(self.head, slice);
+            self.head = self.wrap_add(self.head, slice.len());
+        }
+    }
+}
diff --git a/library/alloc/src/collections/vec_deque/tests.rs b/library/alloc/src/collections/vec_deque/tests.rs
index 2be83f68f01..f2869a54713 100644
--- a/library/alloc/src/collections/vec_deque/tests.rs
+++ b/library/alloc/src/collections/vec_deque/tests.rs
@@ -163,6 +163,300 @@ fn test_insert() {
 }
 
 #[test]
+fn test_get() {
+    let mut tester = VecDeque::new();
+    tester.push_back(1);
+    tester.push_back(2);
+    tester.push_back(3);
+
+    assert_eq!(tester.len(), 3);
+
+    assert_eq!(tester.get(1), Some(&2));
+    assert_eq!(tester.get(2), Some(&3));
+    assert_eq!(tester.get(0), Some(&1));
+    assert_eq!(tester.get(3), None);
+
+    tester.remove(0);
+
+    assert_eq!(tester.len(), 2);
+    assert_eq!(tester.get(0), Some(&2));
+    assert_eq!(tester.get(1), Some(&3));
+    assert_eq!(tester.get(2), None);
+}
+
+#[test]
+fn test_get_mut() {
+    let mut tester = VecDeque::new();
+    tester.push_back(1);
+    tester.push_back(2);
+    tester.push_back(3);
+
+    assert_eq!(tester.len(), 3);
+
+    if let Some(elem) = tester.get_mut(0) {
+        assert_eq!(*elem, 1);
+        *elem = 10;
+    }
+
+    if let Some(elem) = tester.get_mut(2) {
+        assert_eq!(*elem, 3);
+        *elem = 30;
+    }
+
+    assert_eq!(tester.get(0), Some(&10));
+    assert_eq!(tester.get(2), Some(&30));
+    assert_eq!(tester.get_mut(3), None);
+
+    tester.remove(2);
+
+    assert_eq!(tester.len(), 2);
+    assert_eq!(tester.get(0), Some(&10));
+    assert_eq!(tester.get(1), Some(&2));
+    assert_eq!(tester.get(2), None);
+}
+
+#[test]
+fn test_swap() {
+    let mut tester = VecDeque::new();
+    tester.push_back(1);
+    tester.push_back(2);
+    tester.push_back(3);
+
+    assert_eq!(tester, [1, 2, 3]);
+
+    tester.swap(0, 0);
+    assert_eq!(tester, [1, 2, 3]);
+    tester.swap(0, 1);
+    assert_eq!(tester, [2, 1, 3]);
+    tester.swap(2, 1);
+    assert_eq!(tester, [2, 3, 1]);
+    tester.swap(1, 2);
+    assert_eq!(tester, [2, 1, 3]);
+    tester.swap(0, 2);
+    assert_eq!(tester, [3, 1, 2]);
+    tester.swap(2, 2);
+    assert_eq!(tester, [3, 1, 2]);
+}
+
+#[test]
+#[should_panic = "assertion failed: j < self.len()"]
+fn test_swap_panic() {
+    let mut tester = VecDeque::new();
+    tester.push_back(1);
+    tester.push_back(2);
+    tester.push_back(3);
+    tester.swap(2, 3);
+}
+
+#[test]
+fn test_reserve_exact() {
+    let mut tester: VecDeque<i32> = VecDeque::with_capacity(1);
+    assert!(tester.capacity() == 1);
+    tester.reserve_exact(50);
+    assert!(tester.capacity() >= 51);
+    tester.reserve_exact(40);
+    assert!(tester.capacity() >= 51);
+    tester.reserve_exact(200);
+    assert!(tester.capacity() >= 200);
+}
+
+#[test]
+#[should_panic = "capacity overflow"]
+fn test_reserve_exact_panic() {
+    let mut tester: VecDeque<i32> = VecDeque::new();
+    tester.reserve_exact(usize::MAX);
+}
+
+#[test]
+fn test_try_reserve_exact() {
+    let mut tester: VecDeque<i32> = VecDeque::with_capacity(1);
+    assert!(tester.capacity() == 1);
+    assert_eq!(tester.try_reserve_exact(100), Ok(()));
+    assert!(tester.capacity() >= 100);
+    assert_eq!(tester.try_reserve_exact(50), Ok(()));
+    assert!(tester.capacity() >= 100);
+    assert_eq!(tester.try_reserve_exact(200), Ok(()));
+    assert!(tester.capacity() >= 200);
+    assert_eq!(tester.try_reserve_exact(0), Ok(()));
+    assert!(tester.capacity() >= 200);
+    assert!(tester.try_reserve_exact(usize::MAX).is_err());
+}
+
+#[test]
+fn test_try_reserve() {
+    let mut tester: VecDeque<i32> = VecDeque::with_capacity(1);
+    assert!(tester.capacity() == 1);
+    assert_eq!(tester.try_reserve(100), Ok(()));
+    assert!(tester.capacity() >= 100);
+    assert_eq!(tester.try_reserve(50), Ok(()));
+    assert!(tester.capacity() >= 100);
+    assert_eq!(tester.try_reserve(200), Ok(()));
+    assert!(tester.capacity() >= 200);
+    assert_eq!(tester.try_reserve(0), Ok(()));
+    assert!(tester.capacity() >= 200);
+    assert!(tester.try_reserve(usize::MAX).is_err());
+}
+
+#[test]
+fn test_contains() {
+    let mut tester = VecDeque::new();
+    tester.push_back(1);
+    tester.push_back(2);
+    tester.push_back(3);
+
+    assert!(tester.contains(&1));
+    assert!(tester.contains(&3));
+    assert!(!tester.contains(&0));
+    assert!(!tester.contains(&4));
+    tester.remove(0);
+    assert!(!tester.contains(&1));
+    assert!(tester.contains(&2));
+    assert!(tester.contains(&3));
+}
+
+#[test]
+fn test_rotate_left_right() {
+    let mut tester: VecDeque<_> = (1..=10).collect();
+
+    assert_eq!(tester.len(), 10);
+
+    tester.rotate_left(0);
+    assert_eq!(tester, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+
+    tester.rotate_right(0);
+    assert_eq!(tester, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+
+    tester.rotate_left(3);
+    assert_eq!(tester, [4, 5, 6, 7, 8, 9, 10, 1, 2, 3]);
+
+    tester.rotate_right(5);
+    assert_eq!(tester, [9, 10, 1, 2, 3, 4, 5, 6, 7, 8]);
+
+    tester.rotate_left(tester.len());
+    assert_eq!(tester, [9, 10, 1, 2, 3, 4, 5, 6, 7, 8]);
+
+    tester.rotate_right(tester.len());
+    assert_eq!(tester, [9, 10, 1, 2, 3, 4, 5, 6, 7, 8]);
+
+    tester.rotate_left(1);
+    assert_eq!(tester, [10, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+}
+
+#[test]
+#[should_panic = "assertion failed: mid <= self.len()"]
+fn test_rotate_left_panic() {
+    let mut tester: VecDeque<_> = (1..=10).collect();
+    tester.rotate_left(tester.len() + 1);
+}
+
+#[test]
+#[should_panic = "assertion failed: k <= self.len()"]
+fn test_rotate_right_panic() {
+    let mut tester: VecDeque<_> = (1..=10).collect();
+    tester.rotate_right(tester.len() + 1);
+}
+
+#[test]
+fn test_binary_search() {
+    // If the givin VecDeque is not sorted, the returned result is unspecified and meaningless,
+    // as this method performs a binary search.
+
+    let tester: VecDeque<_> = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into();
+
+    assert_eq!(tester.binary_search(&0), Ok(0));
+    assert_eq!(tester.binary_search(&5), Ok(5));
+    assert_eq!(tester.binary_search(&55), Ok(10));
+    assert_eq!(tester.binary_search(&4), Err(5));
+    assert_eq!(tester.binary_search(&-1), Err(0));
+    assert!(matches!(tester.binary_search(&1), Ok(1..=2)));
+
+    let tester: VecDeque<_> = [1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3].into();
+    assert_eq!(tester.binary_search(&1), Ok(0));
+    assert!(matches!(tester.binary_search(&2), Ok(1..=4)));
+    assert!(matches!(tester.binary_search(&3), Ok(5..=13)));
+    assert_eq!(tester.binary_search(&-2), Err(0));
+    assert_eq!(tester.binary_search(&0), Err(0));
+    assert_eq!(tester.binary_search(&4), Err(14));
+    assert_eq!(tester.binary_search(&5), Err(14));
+}
+
+#[test]
+fn test_binary_search_by() {
+    // If the givin VecDeque is not sorted, the returned result is unspecified and meaningless,
+    // as this method performs a binary search.
+
+    let tester: VecDeque<_> = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].into();
+
+    assert_eq!(tester.binary_search_by(|x| x.cmp(&0)), Ok(0));
+    assert_eq!(tester.binary_search_by(|x| x.cmp(&5)), Ok(5));
+    assert_eq!(tester.binary_search_by(|x| x.cmp(&55)), Ok(10));
+    assert_eq!(tester.binary_search_by(|x| x.cmp(&4)), Err(5));
+    assert_eq!(tester.binary_search_by(|x| x.cmp(&-1)), Err(0));
+    assert!(matches!(tester.binary_search_by(|x| x.cmp(&1)), Ok(1..=2)));
+}
+
+#[test]
+fn test_binary_search_key() {
+    // If the givin VecDeque is not sorted, the returned result is unspecified and meaningless,
+    // as this method performs a binary search.
+
+    let tester: VecDeque<_> = [
+        (-1, 0),
+        (2, 10),
+        (6, 5),
+        (7, 1),
+        (8, 10),
+        (10, 2),
+        (20, 3),
+        (24, 5),
+        (25, 18),
+        (28, 13),
+        (31, 21),
+        (32, 4),
+        (54, 25),
+    ]
+    .into();
+
+    assert_eq!(tester.binary_search_by_key(&-1, |&(a, _b)| a), Ok(0));
+    assert_eq!(tester.binary_search_by_key(&8, |&(a, _b)| a), Ok(4));
+    assert_eq!(tester.binary_search_by_key(&25, |&(a, _b)| a), Ok(8));
+    assert_eq!(tester.binary_search_by_key(&54, |&(a, _b)| a), Ok(12));
+    assert_eq!(tester.binary_search_by_key(&-2, |&(a, _b)| a), Err(0));
+    assert_eq!(tester.binary_search_by_key(&1, |&(a, _b)| a), Err(1));
+    assert_eq!(tester.binary_search_by_key(&4, |&(a, _b)| a), Err(2));
+    assert_eq!(tester.binary_search_by_key(&13, |&(a, _b)| a), Err(6));
+    assert_eq!(tester.binary_search_by_key(&55, |&(a, _b)| a), Err(13));
+    assert_eq!(tester.binary_search_by_key(&100, |&(a, _b)| a), Err(13));
+
+    let tester: VecDeque<_> = [
+        (0, 0),
+        (2, 1),
+        (6, 1),
+        (5, 1),
+        (3, 1),
+        (1, 2),
+        (2, 3),
+        (4, 5),
+        (5, 8),
+        (8, 13),
+        (1, 21),
+        (2, 34),
+        (4, 55),
+    ]
+    .into();
+
+    assert_eq!(tester.binary_search_by_key(&0, |&(_a, b)| b), Ok(0));
+    assert!(matches!(tester.binary_search_by_key(&1, |&(_a, b)| b), Ok(1..=4)));
+    assert_eq!(tester.binary_search_by_key(&8, |&(_a, b)| b), Ok(8));
+    assert_eq!(tester.binary_search_by_key(&13, |&(_a, b)| b), Ok(9));
+    assert_eq!(tester.binary_search_by_key(&55, |&(_a, b)| b), Ok(12));
+    assert_eq!(tester.binary_search_by_key(&-1, |&(_a, b)| b), Err(0));
+    assert_eq!(tester.binary_search_by_key(&4, |&(_a, b)| b), Err(7));
+    assert_eq!(tester.binary_search_by_key(&56, |&(_a, b)| b), Err(13));
+    assert_eq!(tester.binary_search_by_key(&100, |&(_a, b)| b), Err(13));
+}
+
+#[test]
 fn make_contiguous_big_tail() {
     let mut tester = VecDeque::with_capacity(15);
 
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index a42f1c3b4bb..4bcc78ae0f4 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -1956,6 +1956,25 @@ where
     }
 }
 
+#[stable(feature = "shared_from_str", since = "1.62.0")]
+impl From<Rc<str>> for Rc<[u8]> {
+    /// Converts a reference-counted string slice into a byte slice.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use std::rc::Rc;
+    /// let string: Rc<str> = Rc::from("eggplant");
+    /// let bytes: Rc<[u8]> = Rc::from(string);
+    /// assert_eq!("eggplant".as_bytes(), bytes.as_ref());
+    /// ```
+    #[inline]
+    fn from(rc: Rc<str>) -> Self {
+        // SAFETY: `str` has the same layout as `[u8]`.
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const [u8]) }
+    }
+}
+
 #[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Rc<[T]>> for Rc<[T; N]> {
     type Error = Rc<[T]>;
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index a19999cd725..1e2caddcacb 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -2556,6 +2556,25 @@ where
     }
 }
 
+#[stable(feature = "shared_from_str", since = "1.62.0")]
+impl From<Arc<str>> for Arc<[u8]> {
+    /// Converts an atomically reference-counted string slice into a byte slice.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use std::sync::Arc;
+    /// let string: Arc<str> = Arc::from("eggplant");
+    /// let bytes: Arc<[u8]> = Arc::from(string);
+    /// assert_eq!("eggplant".as_bytes(), bytes.as_ref());
+    /// ```
+    #[inline]
+    fn from(rc: Arc<str>) -> Self {
+        // SAFETY: `str` has the same layout as `[u8]`.
+        unsafe { Arc::from_raw(Arc::into_raw(rc) as *const [u8]) }
+    }
+}
+
 #[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
 impl<T, const N: usize> TryFrom<Arc<[T]>> for Arc<[T; N]> {
     type Error = Arc<[T]>;
diff --git a/library/alloc/src/vec/into_iter.rs b/library/alloc/src/vec/into_iter.rs
index 03c532bb697..8134eea570a 100644
--- a/library/alloc/src/vec/into_iter.rs
+++ b/library/alloc/src/vec/into_iter.rs
@@ -121,6 +121,11 @@ impl<T, A: Allocator> IntoIter<T, A> {
             ptr::drop_in_place(remaining);
         }
     }
+
+    /// Forgets to Drop the remaining elements while still allowing the backing allocation to be freed.
+    pub(crate) fn forget_remaining_elements(&mut self) {
+        self.ptr = self.end;
+    }
 }
 
 #[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
diff --git a/library/alloc/src/vec/is_zero.rs b/library/alloc/src/vec/is_zero.rs
index 0efc4893c3c..868f2f1e323 100644
--- a/library/alloc/src/vec/is_zero.rs
+++ b/library/alloc/src/vec/is_zero.rs
@@ -2,7 +2,7 @@ use crate::boxed::Box;
 
 #[rustc_specialization_trait]
 pub(super) unsafe trait IsZero {
-    /// Whether this value is zero
+    /// Whether this value's representation is all zeros
     fn is_zero(&self) -> bool;
 }
 
@@ -49,6 +49,13 @@ unsafe impl<T> IsZero for *mut T {
     }
 }
 
+unsafe impl<T: IsZero, const N: usize> IsZero for [T; N] {
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.iter().all(IsZero::is_zero)
+    }
+}
+
 // `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
 // For fat pointers, the bytes that would be the pointer metadata in the `Some`
 // variant are padding in the `None` variant, so ignoring them and
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 9bf42e779c9..3dc8a4fbba8 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -2989,48 +2989,6 @@ impl<T, const N: usize> From<[T; N]> for Vec<T> {
     }
 }
 
-#[cfg(not(no_global_oom_handling))]
-#[stable(feature = "vec_from_array_ref", since = "1.61.0")]
-impl<T: Clone, const N: usize> From<&[T; N]> for Vec<T> {
-    /// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// assert_eq!(Vec::from(b"raw"), vec![b'r', b'a', b'w']);
-    /// ```
-    #[cfg(not(test))]
-    fn from(s: &[T; N]) -> Vec<T> {
-        s.to_vec()
-    }
-
-    #[cfg(test)]
-    fn from(s: &[T; N]) -> Vec<T> {
-        crate::slice::to_vec(s, Global)
-    }
-}
-
-#[cfg(not(no_global_oom_handling))]
-#[stable(feature = "vec_from_array_ref", since = "1.61.0")]
-impl<T: Clone, const N: usize> From<&mut [T; N]> for Vec<T> {
-    /// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// assert_eq!(Vec::from(&mut [1, 2, 3]), vec![1, 2, 3]);
-    /// ```
-    #[cfg(not(test))]
-    fn from(s: &mut [T; N]) -> Vec<T> {
-        s.to_vec()
-    }
-
-    #[cfg(test)]
-    fn from(s: &mut [T; N]) -> Vec<T> {
-        crate::slice::to_vec(s, Global)
-    }
-}
-
 #[stable(feature = "vec_from_cow_slice", since = "1.14.0")]
 impl<'a, T> From<Cow<'a, [T]>> for Vec<T>
 where
diff --git a/library/alloc/src/vec/spec_extend.rs b/library/alloc/src/vec/spec_extend.rs
index c3b4534096d..506ee0ecfa2 100644
--- a/library/alloc/src/vec/spec_extend.rs
+++ b/library/alloc/src/vec/spec_extend.rs
@@ -62,7 +62,7 @@ impl<T, A: Allocator> SpecExtend<T, IntoIter<T>> for Vec<T, A> {
         unsafe {
             self.append_elements(iterator.as_slice() as _);
         }
-        iterator.ptr = iterator.end;
+        iterator.forget_remaining_elements();
     }
 }