Merging upstream version 1.71.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

22 files changed, 447 insertions, 251 deletions

diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index 6f2ba957b..01d1fdc9b 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -37,6 +37,9 @@ extern "Rust" {
     #[rustc_allocator_zeroed]
     #[rustc_nounwind]
     fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
+
+    #[cfg(not(bootstrap))]
+    static __rust_no_alloc_shim_is_unstable: u8;
 }
 
 /// The global memory allocator.
@@ -90,7 +93,14 @@ pub use std::alloc::Global;
 #[must_use = "losing the pointer will leak memory"]
 #[inline]
 pub unsafe fn alloc(layout: Layout) -> *mut u8 {
-    unsafe { __rust_alloc(layout.size(), layout.align()) }
+    unsafe {
+        // Make sure we don't accidentally allow omitting the allocator shim in
+        // stable code until it is actually stabilized.
+        #[cfg(not(bootstrap))]
+        core::ptr::read_volatile(&__rust_no_alloc_shim_is_unstable);
+
+        __rust_alloc(layout.size(), layout.align())
+    }
 }
 
 /// Deallocate memory with the global allocator.
diff --git a/library/alloc/src/borrow.rs b/library/alloc/src/borrow.rs
index 0c8c796ae..84331eba2 100644
--- a/library/alloc/src/borrow.rs
+++ b/library/alloc/src/borrow.rs
@@ -115,7 +115,7 @@ where
 /// ```
 /// use std::borrow::Cow;
 ///
-/// fn abs_all(input: &mut Cow<[i32]>) {
+/// fn abs_all(input: &mut Cow<'_, [i32]>) {
 ///     for i in 0..input.len() {
 ///         let v = input[i];
 ///         if v < 0 {
@@ -145,7 +145,7 @@ where
 /// ```
 /// use std::borrow::Cow;
 ///
-/// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
+/// struct Items<'a, X> where [X]: ToOwned<Owned = Vec<X>> {
 ///     values: Cow<'a, [X]>,
 /// }
 ///
@@ -267,7 +267,7 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
     ///
     /// assert_eq!(
     ///   cow,
-    ///   Cow::Owned(String::from("FOO")) as Cow<str>
+    ///   Cow::Owned(String::from("FOO")) as Cow<'_, str>
     /// );
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -311,7 +311,7 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
     /// use std::borrow::Cow;
     ///
     /// let s = "Hello world!";
-    /// let cow: Cow<str> = Cow::Owned(String::from(s));
+    /// let cow: Cow<'_, str> = Cow::Owned(String::from(s));
     ///
     /// assert_eq!(
     ///   cow.into_owned(),
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index 7f88327bf..1768687e8 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -576,8 +576,7 @@ impl<T, A: Allocator> Box<T, A> {
     ///
     /// This conversion does not allocate on the heap and happens in place.
     #[unstable(feature = "box_into_boxed_slice", issue = "71582")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
-    pub const fn into_boxed_slice(boxed: Self) -> Box<[T], A> {
+    pub fn into_boxed_slice(boxed: Self) -> Box<[T], A> {
         let (raw, alloc) = Box::into_raw_with_allocator(boxed);
         unsafe { Box::from_raw_in(raw as *mut [T; 1], alloc) }
     }
@@ -809,9 +808,8 @@ impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
     /// assert_eq!(*five, 5)
     /// ```
     #[unstable(feature = "new_uninit", issue = "63291")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const unsafe fn assume_init(self) -> Box<T, A> {
+    pub unsafe fn assume_init(self) -> Box<T, A> {
         let (raw, alloc) = Box::into_raw_with_allocator(self);
         unsafe { Box::from_raw_in(raw as *mut T, alloc) }
     }
@@ -844,9 +842,8 @@ impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
     /// }
     /// ```
     #[unstable(feature = "new_uninit", issue = "63291")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn write(mut boxed: Self, value: T) -> Box<T, A> {
+    pub fn write(mut boxed: Self, value: T) -> Box<T, A> {
         unsafe {
             (*boxed).write(value);
             boxed.assume_init()
@@ -1090,9 +1087,8 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     ///
     /// [memory layout]: self#memory-layout
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn into_raw_with_allocator(b: Self) -> (*mut T, A) {
+    pub fn into_raw_with_allocator(b: Self) -> (*mut T, A) {
         let (leaked, alloc) = Box::into_unique(b);
         (leaked.as_ptr(), alloc)
     }
@@ -1102,10 +1098,9 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
         issue = "none",
         reason = "use `Box::leak(b).into()` or `Unique::from(Box::leak(b))` instead"
     )]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
     #[doc(hidden)]
-    pub const fn into_unique(b: Self) -> (Unique<T>, A) {
+    pub fn into_unique(b: Self) -> (Unique<T>, A) {
         // Box is recognized as a "unique pointer" by Stacked Borrows, but internally it is a
         // raw pointer for the type system. Turning it directly into a raw pointer would not be
         // recognized as "releasing" the unique pointer to permit aliased raw accesses,
@@ -1163,9 +1158,8 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     /// assert_eq!(*static_ref, [4, 2, 3]);
     /// ```
     #[stable(feature = "box_leak", since = "1.26.0")]
-    #[rustc_const_unstable(feature = "const_box", issue = "92521")]
     #[inline]
-    pub const fn leak<'a>(b: Self) -> &'a mut T
+    pub fn leak<'a>(b: Self) -> &'a mut T
     where
         A: 'a,
     {
@@ -1234,8 +1228,7 @@ impl<T: Default> Default for Box<T> {
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl<T> const Default for Box<[T]> {
+impl<T> Default for Box<[T]> {
     #[inline]
     fn default() -> Self {
         let ptr: Unique<[T]> = Unique::<[T; 0]>::dangling();
@@ -1245,8 +1238,7 @@ impl<T> const Default for Box<[T]> {
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "default_box_extra", since = "1.17.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl const Default for Box<str> {
+impl Default for Box<str> {
     #[inline]
     fn default() -> Self {
         // SAFETY: This is the same as `Unique::cast<U>` but with an unsized `U = str`.
@@ -1443,8 +1435,7 @@ impl<T> From<T> for Box<T> {
 }
 
 #[stable(feature = "pin", since = "1.33.0")]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
-impl<T: ?Sized, A: Allocator> const From<Box<T, A>> for Pin<Box<T, A>>
+impl<T: ?Sized, A: Allocator> From<Box<T, A>> for Pin<Box<T, A>>
 where
     A: 'static,
 {
@@ -1464,9 +1455,36 @@ where
     }
 }
 
+/// Specialization trait used for `From<&[T]>`.
+#[cfg(not(no_global_oom_handling))]
+trait BoxFromSlice<T> {
+    fn from_slice(slice: &[T]) -> Self;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Clone> BoxFromSlice<T> for Box<[T]> {
+    #[inline]
+    default fn from_slice(slice: &[T]) -> Self {
+        slice.to_vec().into_boxed_slice()
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Copy> BoxFromSlice<T> for Box<[T]> {
+    #[inline]
+    fn from_slice(slice: &[T]) -> Self {
+        let len = slice.len();
+        let buf = RawVec::with_capacity(len);
+        unsafe {
+            ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
+            buf.into_box(slice.len()).assume_init()
+        }
+    }
+}
+
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_slice", since = "1.17.0")]
-impl<T: Copy> From<&[T]> for Box<[T]> {
+impl<T: Clone> From<&[T]> for Box<[T]> {
     /// Converts a `&[T]` into a `Box<[T]>`
     ///
     /// This conversion allocates on the heap
@@ -1480,19 +1498,15 @@ impl<T: Copy> From<&[T]> for Box<[T]> {
     ///
     /// println!("{boxed_slice:?}");
     /// ```
+    #[inline]
     fn from(slice: &[T]) -> Box<[T]> {
-        let len = slice.len();
-        let buf = RawVec::with_capacity(len);
-        unsafe {
-            ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
-            buf.into_box(slice.len()).assume_init()
-        }
+        <Self as BoxFromSlice<T>>::from_slice(slice)
     }
 }
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_cow", since = "1.45.0")]
-impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
+impl<T: Clone> From<Cow<'_, [T]>> for Box<[T]> {
     /// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
     ///
     /// When `cow` is the `Cow::Borrowed` variant, this
@@ -1880,8 +1894,7 @@ impl<T: ?Sized, A: Allocator> fmt::Pointer for Box<T, A> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
-impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> {
+impl<T: ?Sized, A: Allocator> Deref for Box<T, A> {
     type Target = T;
 
     fn deref(&self) -> &T {
@@ -1890,8 +1903,7 @@ impl<T: ?Sized, A: Allocator> const Deref for Box<T, A> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
-impl<T: ?Sized, A: Allocator> const DerefMut for Box<T, A> {
+impl<T: ?Sized, A: Allocator> DerefMut for Box<T, A> {
     fn deref_mut(&mut self) -> &mut T {
         &mut **self
     }
diff --git a/library/alloc/src/boxed/thin.rs b/library/alloc/src/boxed/thin.rs
index ad48315fd..f83c8f83c 100644
--- a/library/alloc/src/boxed/thin.rs
+++ b/library/alloc/src/boxed/thin.rs
@@ -7,7 +7,7 @@ use core::fmt::{self, Debug, Display, Formatter};
 use core::marker::PhantomData;
 #[cfg(not(no_global_oom_handling))]
 use core::marker::Unsize;
-use core::mem;
+use core::mem::{self, SizedTypeProperties};
 use core::ops::{Deref, DerefMut};
 use core::ptr::Pointee;
 use core::ptr::{self, NonNull};
@@ -202,9 +202,7 @@ impl<H> WithHeader<H> {
             let ptr = if layout.size() == 0 {
                 // Some paranoia checking, mostly so that the ThinBox tests are
                 // more able to catch issues.
-                debug_assert!(
-                    value_offset == 0 && mem::size_of::<T>() == 0 && mem::size_of::<H>() == 0
-                );
+                debug_assert!(value_offset == 0 && T::IS_ZST && H::IS_ZST);
                 layout.dangling()
             } else {
                 let ptr = alloc::alloc(layout);
@@ -249,9 +247,7 @@ impl<H> WithHeader<H> {
                         alloc::dealloc(self.ptr.as_ptr().sub(value_offset), layout);
                     } else {
                         debug_assert!(
-                            value_offset == 0
-                                && mem::size_of::<H>() == 0
-                                && self.value_layout.size() == 0
+                            value_offset == 0 && H::IS_ZST && self.value_layout.size() == 0
                         );
                     }
                 }
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index afdc99817..1f8a1ecba 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -1543,11 +1543,17 @@ impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a V)> {
+    fn min(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a V)> {
+    fn max(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next_back()
     }
 }
@@ -1612,11 +1618,17 @@ impl<'a, K, V> Iterator for IterMut<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn min(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn max(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next_back()
     }
 }
@@ -1779,11 +1791,17 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<&'a K> {
+    fn min(mut self) -> Option<&'a K>
+    where
+        &'a K: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<&'a K> {
+    fn max(mut self) -> Option<&'a K>
+    where
+        &'a K: Ord,
+    {
         self.next_back()
     }
 }
@@ -2008,11 +2026,17 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a V)> {
+    fn min(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a V)> {
+    fn max(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next_back()
     }
 }
@@ -2081,11 +2105,17 @@ impl<K, V, A: Allocator + Clone> Iterator for IntoKeys<K, V, A> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<K> {
+    fn min(mut self) -> Option<K>
+    where
+        K: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<K> {
+    fn max(mut self) -> Option<K>
+    where
+        K: Ord,
+    {
         self.next_back()
     }
 }
@@ -2204,11 +2234,17 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn min(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn max(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next_back()
     }
 }
@@ -2985,7 +3021,7 @@ impl<'a, K, V, A> CursorMut<'a, K, V, A> {
         })
     }
 
-    /// Returns a mutable reference to the of the element that the cursor is
+    /// Returns a mutable reference to the key of the element that the cursor is
     /// currently pointing to.
     ///
     /// This returns `None` if the cursor is currently pointing to the
@@ -3043,8 +3079,8 @@ impl<'a, K, V, A> CursorMut<'a, K, V, A> {
                 unsafe { self.root.reborrow() }
                     .as_mut()?
                     .borrow_mut()
-                    .first_leaf_edge()
-                    .next_kv()
+                    .last_leaf_edge()
+                    .next_back_kv()
                     .ok()?
                     .into_kv_valmut()
             }
diff --git a/library/alloc/src/collections/btree/map/tests.rs b/library/alloc/src/collections/btree/map/tests.rs
index da00d83bd..7ecffe3ee 100644
--- a/library/alloc/src/collections/btree/map/tests.rs
+++ b/library/alloc/src/collections/btree/map/tests.rs
@@ -8,6 +8,7 @@ use crate::testing::crash_test::{CrashTestDummy, Panic};
 use crate::testing::ord_chaos::{Cyclic3, Governed, Governor};
 use crate::testing::rng::DeterministicRng;
 use crate::vec::Vec;
+use core::assert_matches::assert_matches;
 use std::cmp::Ordering;
 use std::iter;
 use std::mem;
@@ -2448,3 +2449,21 @@ fn test_cursor_mut_insert_after_4() {
     let mut cur = map.upper_bound_mut(Bound::Included(&2));
     cur.insert_after(4, 'd');
 }
+
+#[test]
+fn cursor_peek_prev_agrees_with_cursor_mut() {
+    let mut map = BTreeMap::from([(1, 1), (2, 2), (3, 3)]);
+
+    let cursor = map.lower_bound(Bound::Excluded(&3));
+    assert!(cursor.key().is_none());
+
+    let prev = cursor.peek_prev();
+    assert_matches!(prev, Some((&3, _)));
+
+    // Shadow names so the two parts of this test match.
+    let mut cursor = map.lower_bound_mut(Bound::Excluded(&3));
+    assert!(cursor.key().is_none());
+
+    let prev = cursor.peek_prev();
+    assert_matches!(prev, Some((&3, _)));
+}
diff --git a/library/alloc/src/collections/btree/set.rs b/library/alloc/src/collections/btree/set.rs
index da952a13f..940fa30af 100644
--- a/library/alloc/src/collections/btree/set.rs
+++ b/library/alloc/src/collections/btree/set.rs
@@ -1501,11 +1501,17 @@ impl<'a, T> Iterator for Iter<'a, T> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<&'a T> {
+    fn min(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<&'a T> {
+    fn max(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next_back()
     }
 }
@@ -1604,11 +1610,17 @@ impl<'a, T> Iterator for Range<'a, T> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<&'a T> {
+    fn min(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<&'a T> {
+    fn max(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next_back()
     }
 }
diff --git a/library/alloc/src/collections/linked_list.rs b/library/alloc/src/collections/linked_list.rs
index 106d05c57..4cd34ac2f 100644
--- a/library/alloc/src/collections/linked_list.rs
+++ b/library/alloc/src/collections/linked_list.rs
@@ -18,9 +18,10 @@ use core::hash::{Hash, Hasher};
 use core::iter::FusedIterator;
 use core::marker::PhantomData;
 use core::mem;
-use core::ptr::NonNull;
+use core::ptr::{NonNull, Unique};
 
 use super::SpecExtend;
+use crate::alloc::{Allocator, Global};
 use crate::boxed::Box;
 
 #[cfg(test)]
@@ -47,11 +48,15 @@ mod tests;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "LinkedList")]
 #[rustc_insignificant_dtor]
-pub struct LinkedList<T> {
+pub struct LinkedList<
+    T,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
     head: Option<NonNull<Node<T>>>,
     tail: Option<NonNull<Node<T>>>,
     len: usize,
-    marker: PhantomData<Box<Node<T>>>,
+    alloc: A,
+    marker: PhantomData<Box<Node<T>, A>>,
 }
 
 struct Node<T> {
@@ -81,6 +86,7 @@ impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
                 head: self.head,
                 tail: self.tail,
                 len: self.len,
+                alloc: Global,
                 marker: PhantomData,
             }))
             .field(&self.len)
@@ -117,6 +123,7 @@ impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
                 head: self.head,
                 tail: self.tail,
                 len: self.len,
+                alloc: Global,
                 marker: PhantomData,
             }))
             .field(&self.len)
@@ -132,12 +139,15 @@ impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
 /// [`into_iter`]: LinkedList::into_iter
 #[derive(Clone)]
 #[stable(feature = "rust1", since = "1.0.0")]
-pub struct IntoIter<T> {
-    list: LinkedList<T>,
+pub struct IntoIter<
+    T,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
+    list: LinkedList<T, A>,
 }
 
 #[stable(feature = "collection_debug", since = "1.17.0")]
-impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("IntoIter").field(&self.list).finish()
     }
@@ -148,22 +158,25 @@ impl<T> Node<T> {
         Node { next: None, prev: None, element }
     }
 
-    fn into_element(self: Box<Self>) -> T {
+    fn into_element<A: Allocator>(self: Box<Self, A>) -> T {
         self.element
     }
 }
 
 // private methods
-impl<T> LinkedList<T> {
+impl<T, A: Allocator> LinkedList<T, A> {
     /// Adds the given node to the front of the list.
+    ///
+    /// # Safety
+    /// `node` must point to a valid node that was boxed using the list's allocator.
     #[inline]
-    fn push_front_node(&mut self, mut node: Box<Node<T>>) {
+    unsafe fn push_front_node(&mut self, node: Unique<Node<T>>) {
         // This method takes care not to create mutable references to whole nodes,
         // to maintain validity of aliasing pointers into `element`.
         unsafe {
-            node.next = self.head;
-            node.prev = None;
-            let node = Some(Box::leak(node).into());
+            (*node.as_ptr()).next = self.head;
+            (*node.as_ptr()).prev = None;
+            let node = Some(NonNull::from(node));
 
             match self.head {
                 None => self.tail = node,
@@ -178,11 +191,11 @@ impl<T> LinkedList<T> {
 
     /// Removes and returns the node at the front of the list.
     #[inline]
-    fn pop_front_node(&mut self) -> Option<Box<Node<T>>> {
+    fn pop_front_node(&mut self) -> Option<Box<Node<T>, &A>> {
         // This method takes care not to create mutable references to whole nodes,
         // to maintain validity of aliasing pointers into `element`.
         self.head.map(|node| unsafe {
-            let node = Box::from_raw(node.as_ptr());
+            let node = Box::from_raw_in(node.as_ptr(), &self.alloc);
             self.head = node.next;
 
             match self.head {
@@ -197,14 +210,17 @@ impl<T> LinkedList<T> {
     }
 
     /// Adds the given node to the back of the list.
+    ///
+    /// # Safety
+    /// `node` must point to a valid node that was boxed using the list's allocator.
     #[inline]
-    fn push_back_node(&mut self, mut node: Box<Node<T>>) {
+    unsafe fn push_back_node(&mut self, node: Unique<Node<T>>) {
         // This method takes care not to create mutable references to whole nodes,
         // to maintain validity of aliasing pointers into `element`.
         unsafe {
-            node.next = None;
-            node.prev = self.tail;
-            let node = Some(Box::leak(node).into());
+            (*node.as_ptr()).next = None;
+            (*node.as_ptr()).prev = self.tail;
+            let node = Some(NonNull::from(node));
 
             match self.tail {
                 None => self.head = node,
@@ -219,11 +235,11 @@ impl<T> LinkedList<T> {
 
     /// Removes and returns the node at the back of the list.
     #[inline]
-    fn pop_back_node(&mut self) -> Option<Box<Node<T>>> {
+    fn pop_back_node(&mut self) -> Option<Box<Node<T>, &A>> {
         // This method takes care not to create mutable references to whole nodes,
         // to maintain validity of aliasing pointers into `element`.
         self.tail.map(|node| unsafe {
-            let node = Box::from_raw(node.as_ptr());
+            let node = Box::from_raw_in(node.as_ptr(), &self.alloc);
             self.tail = node.prev;
 
             match self.tail {
@@ -321,7 +337,10 @@ impl<T> LinkedList<T> {
         &mut self,
         split_node: Option<NonNull<Node<T>>>,
         at: usize,
-    ) -> Self {
+    ) -> Self
+    where
+        A: Clone,
+    {
         // The split node is the new head node of the second part
         if let Some(mut split_node) = split_node {
             let first_part_head;
@@ -342,6 +361,7 @@ impl<T> LinkedList<T> {
                 head: first_part_head,
                 tail: first_part_tail,
                 len: at,
+                alloc: self.alloc.clone(),
                 marker: PhantomData,
             };
 
@@ -351,7 +371,7 @@ impl<T> LinkedList<T> {
 
             first_part
         } else {
-            mem::replace(self, LinkedList::new())
+            mem::replace(self, LinkedList::new_in(self.alloc.clone()))
         }
     }
 
@@ -360,7 +380,10 @@ impl<T> LinkedList<T> {
         &mut self,
         split_node: Option<NonNull<Node<T>>>,
         at: usize,
-    ) -> Self {
+    ) -> Self
+    where
+        A: Clone,
+    {
         // The split node is the new tail node of the first part and owns
         // the head of the second part.
         if let Some(mut split_node) = split_node {
@@ -382,6 +405,7 @@ impl<T> LinkedList<T> {
                 head: second_part_head,
                 tail: second_part_tail,
                 len: self.len - at,
+                alloc: self.alloc.clone(),
                 marker: PhantomData,
             };
 
@@ -391,7 +415,7 @@ impl<T> LinkedList<T> {
 
             second_part
         } else {
-            mem::replace(self, LinkedList::new())
+            mem::replace(self, LinkedList::new_in(self.alloc.clone()))
         }
     }
 }
@@ -420,7 +444,7 @@ impl<T> LinkedList<T> {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use]
     pub const fn new() -> Self {
-        LinkedList { head: None, tail: None, len: 0, marker: PhantomData }
+        LinkedList { head: None, tail: None, len: 0, alloc: Global, marker: PhantomData }
     }
 
     /// Moves all elements from `other` to the end of the list.
@@ -471,7 +495,26 @@ impl<T> LinkedList<T> {
             }
         }
     }
+}
 
+impl<T, A: Allocator> LinkedList<T, A> {
+    /// Constructs an empty `LinkedList<T, A>`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(allocator_api)]
+    ///
+    /// use std::alloc::System;
+    /// use std::collections::LinkedList;
+    ///
+    /// let list: LinkedList<u32, _> = LinkedList::new_in(System);
+    /// ```
+    #[inline]
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    pub const fn new_in(alloc: A) -> Self {
+        LinkedList { head: None, tail: None, len: 0, alloc, marker: PhantomData }
+    }
     /// Provides a forward iterator.
     ///
     /// # Examples
@@ -532,7 +575,7 @@ impl<T> LinkedList<T> {
     #[inline]
     #[must_use]
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn cursor_front(&self) -> Cursor<'_, T> {
+    pub fn cursor_front(&self) -> Cursor<'_, T, A> {
         Cursor { index: 0, current: self.head, list: self }
     }
 
@@ -542,7 +585,7 @@ impl<T> LinkedList<T> {
     #[inline]
     #[must_use]
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn cursor_front_mut(&mut self) -> CursorMut<'_, T> {
+    pub fn cursor_front_mut(&mut self) -> CursorMut<'_, T, A> {
         CursorMut { index: 0, current: self.head, list: self }
     }
 
@@ -552,7 +595,7 @@ impl<T> LinkedList<T> {
     #[inline]
     #[must_use]
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn cursor_back(&self) -> Cursor<'_, T> {
+    pub fn cursor_back(&self) -> Cursor<'_, T, A> {
         Cursor { index: self.len.checked_sub(1).unwrap_or(0), current: self.tail, list: self }
     }
 
@@ -562,7 +605,7 @@ impl<T> LinkedList<T> {
     #[inline]
     #[must_use]
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn cursor_back_mut(&mut self) -> CursorMut<'_, T> {
+    pub fn cursor_back_mut(&mut self) -> CursorMut<'_, T, A> {
         CursorMut { index: self.len.checked_sub(1).unwrap_or(0), current: self.tail, list: self }
     }
 
@@ -638,7 +681,15 @@ impl<T> LinkedList<T> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn clear(&mut self) {
-        *self = Self::new();
+        // We need to drop the nodes while keeping self.alloc
+        // We can do this by moving (head, tail, len) into a new list that borrows self.alloc
+        drop(LinkedList {
+            head: self.head.take(),
+            tail: self.tail.take(),
+            len: mem::take(&mut self.len),
+            alloc: &self.alloc,
+            marker: PhantomData,
+        });
     }
 
     /// Returns `true` if the `LinkedList` contains an element equal to the
@@ -790,7 +841,12 @@ impl<T> LinkedList<T> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn push_front(&mut self, elt: T) {
-        self.push_front_node(Box::new(Node::new(elt)));
+        let node = Box::new_in(Node::new(elt), &self.alloc);
+        let node_ptr = Unique::from(Box::leak(node));
+        // SAFETY: node_ptr is a unique pointer to a node we boxed with self.alloc
+        unsafe {
+            self.push_front_node(node_ptr);
+        }
     }
 
     /// Removes the first element and returns it, or `None` if the list is
@@ -833,7 +889,12 @@ impl<T> LinkedList<T> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn push_back(&mut self, elt: T) {
-        self.push_back_node(Box::new(Node::new(elt)));
+        let node = Box::new_in(Node::new(elt), &self.alloc);
+        let node_ptr = Unique::from(Box::leak(node));
+        // SAFETY: node_ptr is a unique pointer to a node we boxed with self.alloc
+        unsafe {
+            self.push_back_node(node_ptr);
+        }
     }
 
     /// Removes the last element from a list and returns it, or `None` if
@@ -883,13 +944,16 @@ impl<T> LinkedList<T> {
     /// assert_eq!(split.pop_front(), None);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn split_off(&mut self, at: usize) -> LinkedList<T> {
+    pub fn split_off(&mut self, at: usize) -> LinkedList<T, A>
+    where
+        A: Clone,
+    {
         let len = self.len();
         assert!(at <= len, "Cannot split off at a nonexistent index");
         if at == 0 {
-            return mem::take(self);
+            return mem::replace(self, Self::new_in(self.alloc.clone()));
         } else if at == len {
-            return Self::new();
+            return Self::new_in(self.alloc.clone());
         }
 
         // Below, we iterate towards the `i-1`th node, either from the start or the end,
@@ -987,7 +1051,7 @@ impl<T> LinkedList<T> {
     /// assert_eq!(odds.into_iter().collect::<Vec<_>>(), vec![1, 3, 5, 9, 11, 13, 15]);
     /// ```
     #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
-    pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F>
+    pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F, A>
     where
         F: FnMut(&mut T) -> bool,
     {
@@ -1000,11 +1064,11 @@ impl<T> LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-unsafe impl<#[may_dangle] T> Drop for LinkedList<T> {
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for LinkedList<T, A> {
     fn drop(&mut self) {
-        struct DropGuard<'a, T>(&'a mut LinkedList<T>);
+        struct DropGuard<'a, T, A: Allocator>(&'a mut LinkedList<T, A>);
 
-        impl<'a, T> Drop for DropGuard<'a, T> {
+        impl<'a, T, A: Allocator> Drop for DropGuard<'a, T, A> {
             fn drop(&mut self) {
                 // Continue the same loop we do below. This only runs when a destructor has
                 // panicked. If another one panics this will abort.
@@ -1012,11 +1076,10 @@ unsafe impl<#[may_dangle] T> Drop for LinkedList<T> {
             }
         }
 
-        while let Some(node) = self.pop_front_node() {
-            let guard = DropGuard(self);
-            drop(node);
-            mem::forget(guard);
-        }
+        // Wrap self so that if a destructor panics, we can try to keep looping
+        let guard = DropGuard(self);
+        while guard.0.pop_front_node().is_some() {}
+        mem::forget(guard);
     }
 }
 
@@ -1159,14 +1222,18 @@ impl<T> Default for IterMut<'_, T> {
 ///
 /// When created, cursors start at the front of the list, or the "ghost" non-element if the list is empty.
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-pub struct Cursor<'a, T: 'a> {
+pub struct Cursor<
+    'a,
+    T: 'a,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
     index: usize,
     current: Option<NonNull<Node<T>>>,
-    list: &'a LinkedList<T>,
+    list: &'a LinkedList<T, A>,
 }
 
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-impl<T> Clone for Cursor<'_, T> {
+impl<T, A: Allocator> Clone for Cursor<'_, T, A> {
     fn clone(&self) -> Self {
         let Cursor { index, current, list } = *self;
         Cursor { index, current, list }
@@ -1174,7 +1241,7 @@ impl<T> Clone for Cursor<'_, T> {
 }
 
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-impl<T: fmt::Debug> fmt::Debug for Cursor<'_, T> {
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for Cursor<'_, T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("Cursor").field(&self.list).field(&self.index()).finish()
     }
@@ -1191,20 +1258,24 @@ impl<T: fmt::Debug> fmt::Debug for Cursor<'_, T> {
 /// To accommodate this, there is a "ghost" non-element that yields `None` between the head and
 /// tail of the list.
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-pub struct CursorMut<'a, T: 'a> {
+pub struct CursorMut<
+    'a,
+    T: 'a,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> {
     index: usize,
     current: Option<NonNull<Node<T>>>,
-    list: &'a mut LinkedList<T>,
+    list: &'a mut LinkedList<T, A>,
 }
 
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-impl<T: fmt::Debug> fmt::Debug for CursorMut<'_, T> {
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for CursorMut<'_, T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("CursorMut").field(&self.list).field(&self.index()).finish()
     }
 }
 
-impl<'a, T> Cursor<'a, T> {
+impl<'a, T, A: Allocator> Cursor<'a, T, A> {
     /// Returns the cursor position index within the `LinkedList`.
     ///
     /// This returns `None` if the cursor is currently pointing to the
@@ -1321,7 +1392,7 @@ impl<'a, T> Cursor<'a, T> {
     }
 }
 
-impl<'a, T> CursorMut<'a, T> {
+impl<'a, T, A: Allocator> CursorMut<'a, T, A> {
     /// Returns the cursor position index within the `LinkedList`.
     ///
     /// This returns `None` if the cursor is currently pointing to the
@@ -1426,7 +1497,7 @@ impl<'a, T> CursorMut<'a, T> {
     /// `CursorMut` is frozen for the lifetime of the `Cursor`.
     #[must_use]
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn as_cursor(&self) -> Cursor<'_, T> {
+    pub fn as_cursor(&self) -> Cursor<'_, T, A> {
         Cursor { list: self.list, current: self.current, index: self.index }
     }
 }
@@ -1434,6 +1505,51 @@ impl<'a, T> CursorMut<'a, T> {
 // Now the list editing operations
 
 impl<'a, T> CursorMut<'a, T> {
+    /// Inserts the elements from the given `LinkedList` after the current one.
+    ///
+    /// If the cursor is pointing at the "ghost" non-element then the new elements are
+    /// inserted at the start of the `LinkedList`.
+    #[unstable(feature = "linked_list_cursors", issue = "58533")]
+    pub fn splice_after(&mut self, list: LinkedList<T>) {
+        unsafe {
+            let (splice_head, splice_tail, splice_len) = match list.detach_all_nodes() {
+                Some(parts) => parts,
+                _ => return,
+            };
+            let node_next = match self.current {
+                None => self.list.head,
+                Some(node) => node.as_ref().next,
+            };
+            self.list.splice_nodes(self.current, node_next, splice_head, splice_tail, splice_len);
+            if self.current.is_none() {
+                // The "ghost" non-element's index has changed.
+                self.index = self.list.len;
+            }
+        }
+    }
+
+    /// Inserts the elements from the given `LinkedList` before the current one.
+    ///
+    /// If the cursor is pointing at the "ghost" non-element then the new elements are
+    /// inserted at the end of the `LinkedList`.
+    #[unstable(feature = "linked_list_cursors", issue = "58533")]
+    pub fn splice_before(&mut self, list: LinkedList<T>) {
+        unsafe {
+            let (splice_head, splice_tail, splice_len) = match list.detach_all_nodes() {
+                Some(parts) => parts,
+                _ => return,
+            };
+            let node_prev = match self.current {
+                None => self.list.tail,
+                Some(node) => node.as_ref().prev,
+            };
+            self.list.splice_nodes(node_prev, self.current, splice_head, splice_tail, splice_len);
+            self.index += splice_len;
+        }
+    }
+}
+
+impl<'a, T, A: Allocator> CursorMut<'a, T, A> {
     /// Inserts a new element into the `LinkedList` after the current one.
     ///
     /// If the cursor is pointing at the "ghost" non-element then the new element is
@@ -1441,7 +1557,7 @@ impl<'a, T> CursorMut<'a, T> {
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
     pub fn insert_after(&mut self, item: T) {
         unsafe {
-            let spliced_node = Box::leak(Box::new(Node::new(item))).into();
+            let spliced_node = Box::leak(Box::new_in(Node::new(item), &self.list.alloc)).into();
             let node_next = match self.current {
                 None => self.list.head,
                 Some(node) => node.as_ref().next,
@@ -1461,7 +1577,7 @@ impl<'a, T> CursorMut<'a, T> {
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
     pub fn insert_before(&mut self, item: T) {
         unsafe {
-            let spliced_node = Box::leak(Box::new(Node::new(item))).into();
+            let spliced_node = Box::leak(Box::new_in(Node::new(item), &self.list.alloc)).into();
             let node_prev = match self.current {
                 None => self.list.tail,
                 Some(node) => node.as_ref().prev,
@@ -1497,7 +1613,10 @@ impl<'a, T> CursorMut<'a, T> {
     /// If the cursor is currently pointing to the "ghost" non-element then no element
     /// is removed and `None` is returned.
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn remove_current_as_list(&mut self) -> Option<LinkedList<T>> {
+    pub fn remove_current_as_list(&mut self) -> Option<LinkedList<T, A>>
+    where
+        A: Clone,
+    {
         let mut unlinked_node = self.current?;
         unsafe {
             self.current = unlinked_node.as_ref().next;
@@ -1509,54 +1628,12 @@ impl<'a, T> CursorMut<'a, T> {
                 head: Some(unlinked_node),
                 tail: Some(unlinked_node),
                 len: 1,
+                alloc: self.list.alloc.clone(),
                 marker: PhantomData,
             })
         }
     }
 
-    /// Inserts the elements from the given `LinkedList` after the current one.
-    ///
-    /// If the cursor is pointing at the "ghost" non-element then the new elements are
-    /// inserted at the start of the `LinkedList`.
-    #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn splice_after(&mut self, list: LinkedList<T>) {
-        unsafe {
-            let (splice_head, splice_tail, splice_len) = match list.detach_all_nodes() {
-                Some(parts) => parts,
-                _ => return,
-            };
-            let node_next = match self.current {
-                None => self.list.head,
-                Some(node) => node.as_ref().next,
-            };
-            self.list.splice_nodes(self.current, node_next, splice_head, splice_tail, splice_len);
-            if self.current.is_none() {
-                // The "ghost" non-element's index has changed.
-                self.index = self.list.len;
-            }
-        }
-    }
-
-    /// Inserts the elements from the given `LinkedList` before the current one.
-    ///
-    /// If the cursor is pointing at the "ghost" non-element then the new elements are
-    /// inserted at the end of the `LinkedList`.
-    #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn splice_before(&mut self, list: LinkedList<T>) {
-        unsafe {
-            let (splice_head, splice_tail, splice_len) = match list.detach_all_nodes() {
-                Some(parts) => parts,
-                _ => return,
-            };
-            let node_prev = match self.current {
-                None => self.list.tail,
-                Some(node) => node.as_ref().prev,
-            };
-            self.list.splice_nodes(node_prev, self.current, splice_head, splice_tail, splice_len);
-            self.index += splice_len;
-        }
-    }
-
     /// Splits the list into two after the current element. This will return a
     /// new list consisting of everything after the cursor, with the original
     /// list retaining everything before.
@@ -1564,7 +1641,10 @@ impl<'a, T> CursorMut<'a, T> {
     /// If the cursor is pointing at the "ghost" non-element then the entire contents
     /// of the `LinkedList` are moved.
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn split_after(&mut self) -> LinkedList<T> {
+    pub fn split_after(&mut self) -> LinkedList<T, A>
+    where
+        A: Clone,
+    {
         let split_off_idx = if self.index == self.list.len { 0 } else { self.index + 1 };
         if self.index == self.list.len {
             // The "ghost" non-element's index has changed to 0.
@@ -1580,7 +1660,10 @@ impl<'a, T> CursorMut<'a, T> {
     /// If the cursor is pointing at the "ghost" non-element then the entire contents
     /// of the `LinkedList` are moved.
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
-    pub fn split_before(&mut self) -> LinkedList<T> {
+    pub fn split_before(&mut self) -> LinkedList<T, A>
+    where
+        A: Clone,
+    {
         let split_off_idx = self.index;
         self.index = 0;
         unsafe { self.list.split_off_before_node(self.current, split_off_idx) }
@@ -1722,11 +1805,15 @@ impl<'a, T> CursorMut<'a, T> {
 
 /// An iterator produced by calling `drain_filter` on LinkedList.
 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
-pub struct DrainFilter<'a, T: 'a, F: 'a>
-where
+pub struct DrainFilter<
+    'a,
+    T: 'a,
+    F: 'a,
+    #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
+> where
     F: FnMut(&mut T) -> bool,
 {
-    list: &'a mut LinkedList<T>,
+    list: &'a mut LinkedList<T, A>,
     it: Option<NonNull<Node<T>>>,
     pred: F,
     idx: usize,
@@ -1734,7 +1821,7 @@ where
 }
 
 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
-impl<T, F> Iterator for DrainFilter<'_, T, F>
+impl<T, F, A: Allocator> Iterator for DrainFilter<'_, T, F, A>
 where
     F: FnMut(&mut T) -> bool,
 {
@@ -1763,16 +1850,16 @@ where
 }
 
 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
-impl<T, F> Drop for DrainFilter<'_, T, F>
+impl<T, F, A: Allocator> Drop for DrainFilter<'_, T, F, A>
 where
     F: FnMut(&mut T) -> bool,
 {
     fn drop(&mut self) {
-        struct DropGuard<'r, 'a, T, F>(&'r mut DrainFilter<'a, T, F>)
+        struct DropGuard<'r, 'a, T, F, A: Allocator>(&'r mut DrainFilter<'a, T, F, A>)
         where
             F: FnMut(&mut T) -> bool;
 
-        impl<'r, 'a, T, F> Drop for DropGuard<'r, 'a, T, F>
+        impl<'r, 'a, T, F, A: Allocator> Drop for DropGuard<'r, 'a, T, F, A>
         where
             F: FnMut(&mut T) -> bool,
         {
@@ -1800,7 +1887,7 @@ where
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Iterator for IntoIter<T> {
+impl<T, A: Allocator> Iterator for IntoIter<T, A> {
     type Item = T;
 
     #[inline]
@@ -1815,7 +1902,7 @@ impl<T> Iterator for IntoIter<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> DoubleEndedIterator for IntoIter<T> {
+impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
     #[inline]
     fn next_back(&mut self) -> Option<T> {
         self.list.pop_back()
@@ -1823,10 +1910,10 @@ impl<T> DoubleEndedIterator for IntoIter<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> ExactSizeIterator for IntoIter<T> {}
+impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {}
 
 #[stable(feature = "fused", since = "1.26.0")]
-impl<T> FusedIterator for IntoIter<T> {}
+impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
 
 #[stable(feature = "default_iters", since = "1.70.0")]
 impl<T> Default for IntoIter<T> {
@@ -1852,19 +1939,19 @@ impl<T> FromIterator<T> for LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> IntoIterator for LinkedList<T> {
+impl<T, A: Allocator> IntoIterator for LinkedList<T, A> {
     type Item = T;
-    type IntoIter = IntoIter<T>;
+    type IntoIter = IntoIter<T, A>;
 
     /// Consumes the list into an iterator yielding elements by value.
     #[inline]
-    fn into_iter(self) -> IntoIter<T> {
+    fn into_iter(self) -> IntoIter<T, A> {
         IntoIter { list: self }
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T> IntoIterator for &'a LinkedList<T> {
+impl<'a, T, A: Allocator> IntoIterator for &'a LinkedList<T, A> {
     type Item = &'a T;
     type IntoIter = Iter<'a, T>;
 
@@ -1874,7 +1961,7 @@ impl<'a, T> IntoIterator for &'a LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T> IntoIterator for &'a mut LinkedList<T> {
+impl<'a, T, A: Allocator> IntoIterator for &'a mut LinkedList<T, A> {
     type Item = &'a mut T;
     type IntoIter = IterMut<'a, T>;
 
@@ -1884,7 +1971,7 @@ impl<'a, T> IntoIterator for &'a mut LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Extend<T> for LinkedList<T> {
+impl<T, A: Allocator> Extend<T> for LinkedList<T, A> {
     fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
         <Self as SpecExtend<I>>::spec_extend(self, iter);
     }
@@ -1895,7 +1982,7 @@ impl<T> Extend<T> for LinkedList<T> {
     }
 }
 
-impl<I: IntoIterator> SpecExtend<I> for LinkedList<I::Item> {
+impl<I: IntoIterator, A: Allocator> SpecExtend<I> for LinkedList<I::Item, A> {
     default fn spec_extend(&mut self, iter: I) {
         iter.into_iter().for_each(move |elt| self.push_back(elt));
     }
@@ -1908,7 +1995,7 @@ impl<T> SpecExtend<LinkedList<T>> for LinkedList<T> {
 }
 
 #[stable(feature = "extend_ref", since = "1.2.0")]
-impl<'a, T: 'a + Copy> Extend<&'a T> for LinkedList<T> {
+impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for LinkedList<T, A> {
     fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
         self.extend(iter.into_iter().cloned());
     }
@@ -1920,7 +2007,7 @@ impl<'a, T: 'a + Copy> Extend<&'a T> for LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: PartialEq> PartialEq for LinkedList<T> {
+impl<T: PartialEq, A: Allocator> PartialEq for LinkedList<T, A> {
     fn eq(&self, other: &Self) -> bool {
         self.len() == other.len() && self.iter().eq(other)
     }
@@ -1931,17 +2018,17 @@ impl<T: PartialEq> PartialEq for LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Eq> Eq for LinkedList<T> {}
+impl<T: Eq, A: Allocator> Eq for LinkedList<T, A> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: PartialOrd> PartialOrd for LinkedList<T> {
+impl<T: PartialOrd, A: Allocator> PartialOrd for LinkedList<T, A> {
     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
         self.iter().partial_cmp(other)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Ord> Ord for LinkedList<T> {
+impl<T: Ord, A: Allocator> Ord for LinkedList<T, A> {
     #[inline]
     fn cmp(&self, other: &Self) -> Ordering {
         self.iter().cmp(other)
@@ -1949,9 +2036,11 @@ impl<T: Ord> Ord for LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Clone> Clone for LinkedList<T> {
+impl<T: Clone, A: Allocator + Clone> Clone for LinkedList<T, A> {
     fn clone(&self) -> Self {
-        self.iter().cloned().collect()
+        let mut list = Self::new_in(self.alloc.clone());
+        list.extend(self.iter().cloned());
+        list
     }
 
     fn clone_from(&mut self, other: &Self) {
@@ -1969,14 +2058,14 @@ impl<T: Clone> Clone for LinkedList<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: fmt::Debug> fmt::Debug for LinkedList<T> {
+impl<T: fmt::Debug, A: Allocator> fmt::Debug for LinkedList<T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_list().entries(self).finish()
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: Hash> Hash for LinkedList<T> {
+impl<T: Hash, A: Allocator> Hash for LinkedList<T, A> {
     fn hash<H: Hasher>(&self, state: &mut H) {
         state.write_length_prefix(self.len());
         for elt in self {
@@ -2016,10 +2105,10 @@ fn assert_covariance() {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-unsafe impl<T: Send> Send for LinkedList<T> {}
+unsafe impl<T: Send, A: Allocator + Send> Send for LinkedList<T, A> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-unsafe impl<T: Sync> Sync for LinkedList<T> {}
+unsafe impl<T: Sync, A: Allocator + Sync> Sync for LinkedList<T, A> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<T: Sync> Send for Iter<'_, T> {}
@@ -2034,13 +2123,13 @@ unsafe impl<T: Send> Send for IterMut<'_, T> {}
 unsafe impl<T: Sync> Sync for IterMut<'_, T> {}
 
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-unsafe impl<T: Sync> Send for Cursor<'_, T> {}
+unsafe impl<T: Sync, A: Allocator + Sync> Send for Cursor<'_, T, A> {}
 
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-unsafe impl<T: Sync> Sync for Cursor<'_, T> {}
+unsafe impl<T: Sync, A: Allocator + Sync> Sync for Cursor<'_, T, A> {}
 
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-unsafe impl<T: Send> Send for CursorMut<'_, T> {}
+unsafe impl<T: Send, A: Allocator + Send> Send for CursorMut<'_, T, A> {}
 
 #[unstable(feature = "linked_list_cursors", issue = "58533")]
-unsafe impl<T: Sync> Sync for CursorMut<'_, T> {}
+unsafe impl<T: Sync, A: Allocator + Sync> Sync for CursorMut<'_, T, A> {}
diff --git a/library/alloc/src/collections/vec_deque/mod.rs b/library/alloc/src/collections/vec_deque/mod.rs
index 8916b42ed..896da37f9 100644
--- a/library/alloc/src/collections/vec_deque/mod.rs
+++ b/library/alloc/src/collections/vec_deque/mod.rs
@@ -2815,7 +2815,7 @@ impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for VecDeque<T, A> {
     }
 
     #[inline]
-    fn extend_one(&mut self, &elem: &T) {
+    fn extend_one(&mut self, &elem: &'a T) {
         self.push_back(elem);
     }
 
diff --git a/library/alloc/src/collections/vec_deque/spec_from_iter.rs b/library/alloc/src/collections/vec_deque/spec_from_iter.rs
index 7650492eb..2708c7fe1 100644
--- a/library/alloc/src/collections/vec_deque/spec_from_iter.rs
+++ b/library/alloc/src/collections/vec_deque/spec_from_iter.rs
@@ -12,7 +12,7 @@ where
     default fn spec_from_iter(iterator: I) -> Self {
         // Since converting is O(1) now, just re-use the `Vec` logic for
         // anything where we can't do something extra-special for `VecDeque`,
-        // especially as that could save us some monomorphiziation work
+        // especially as that could save us some monomorphization work
         // if one uses the same iterators (like slice ones) with both.
         crate::vec::Vec::from_iter(iterator).into()
     }
diff --git a/library/alloc/src/fmt.rs b/library/alloc/src/fmt.rs
index 1da86e1a4..fb8d00e8d 100644
--- a/library/alloc/src/fmt.rs
+++ b/library/alloc/src/fmt.rs
@@ -363,7 +363,7 @@
 //! # use std::fmt;
 //! # struct Foo; // our custom type
 //! # impl fmt::Display for Foo {
-//! fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//! fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 //! # write!(f, "testing, testing")
 //! # } }
 //! ```
@@ -399,7 +399,7 @@
 //! }
 //!
 //! impl fmt::Display for Vector2D {
-//!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//!     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 //!         // The `f` value implements the `Write` trait, which is what the
 //!         // write! macro is expecting. Note that this formatting ignores the
 //!         // various flags provided to format strings.
@@ -410,7 +410,7 @@
 //! // Different traits allow different forms of output of a type. The meaning
 //! // of this format is to print the magnitude of a vector.
 //! impl fmt::Binary for Vector2D {
-//!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//!     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 //!         let magnitude = (self.x * self.x + self.y * self.y) as f64;
 //!         let magnitude = magnitude.sqrt();
 //!
@@ -517,7 +517,7 @@
 //! let mut some_writer = io::stdout();
 //! write!(&mut some_writer, "{}", format_args!("print with a {}", "macro"));
 //!
-//! fn my_fmt_fn(args: fmt::Arguments) {
+//! fn my_fmt_fn(args: fmt::Arguments<'_>) {
 //!     write!(&mut io::stdout(), "{args}");
 //! }
 //! my_fmt_fn(format_args!(", or a {} too", "function"));
@@ -551,8 +551,6 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#[unstable(feature = "fmt_internals", issue = "none")]
-pub use core::fmt::rt;
 #[stable(feature = "fmt_flags_align", since = "1.28.0")]
 pub use core::fmt::Alignment;
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index aa240c37e..59fa91c10 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -101,19 +101,18 @@
 #![feature(array_into_iter_constructors)]
 #![feature(array_methods)]
 #![feature(array_windows)]
+#![feature(ascii_char)]
 #![feature(assert_matches)]
 #![feature(async_iterator)]
 #![feature(coerce_unsized)]
 #![feature(const_align_of_val)]
 #![feature(const_box)]
-#![feature(const_convert)]
 #![feature(const_cow_is_borrowed)]
 #![feature(const_eval_select)]
 #![feature(const_maybe_uninit_as_mut_ptr)]
 #![feature(const_maybe_uninit_write)]
 #![feature(const_maybe_uninit_zeroed)]
 #![feature(const_pin)]
-#![feature(const_ptr_read)]
 #![feature(const_refs_to_cell)]
 #![feature(const_size_of_val)]
 #![feature(const_waker)]
@@ -174,7 +173,6 @@
 #![feature(associated_type_bounds)]
 #![feature(c_unwind)]
 #![feature(cfg_sanitize)]
-#![feature(const_deref)]
 #![feature(const_mut_refs)]
 #![feature(const_precise_live_drops)]
 #![feature(const_ptr_write)]
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index ba035fb06..38a711ac7 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -2039,7 +2039,7 @@ where
     /// ```rust
     /// # use std::rc::Rc;
     /// # use std::borrow::Cow;
-    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
     /// let shared: Rc<str> = Rc::from(cow);
     /// assert_eq!("eggplant", &shared[..]);
     /// ```
diff --git a/library/alloc/src/str.rs b/library/alloc/src/str.rs
index b87ef59f6..849774099 100644
--- a/library/alloc/src/str.rs
+++ b/library/alloc/src/str.rs
@@ -404,12 +404,12 @@ impl str {
             // See https://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992
             // for the definition of `Final_Sigma`.
             debug_assert!('Σ'.len_utf8() == 2);
-            let is_word_final = case_ignoreable_then_cased(from[..i].chars().rev())
-                && !case_ignoreable_then_cased(from[i + 2..].chars());
+            let is_word_final = case_ignorable_then_cased(from[..i].chars().rev())
+                && !case_ignorable_then_cased(from[i + 2..].chars());
             to.push_str(if is_word_final { "ς" } else { "σ" });
         }
 
-        fn case_ignoreable_then_cased<I: Iterator<Item = char>>(iter: I) -> bool {
+        fn case_ignorable_then_cased<I: Iterator<Item = char>>(iter: I) -> bool {
             use core::unicode::{Case_Ignorable, Cased};
             match iter.skip_while(|&c| Case_Ignorable(c)).next() {
                 Some(c) => Cased(c),
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index be41919b9..59e3f887b 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -1851,7 +1851,7 @@ impl String {
     }
 
     /// Consumes and leaks the `String`, returning a mutable reference to the contents,
-    /// `&'static mut str`.
+    /// `&'a mut str`.
     ///
     /// This is mainly useful for data that lives for the remainder of
     /// the program's life. Dropping the returned reference will cause a memory
@@ -1874,7 +1874,7 @@ impl String {
     /// ```
     #[unstable(feature = "string_leak", issue = "102929")]
     #[inline]
-    pub fn leak(self) -> &'static mut str {
+    pub fn leak<'a>(self) -> &'a mut str {
         let slice = self.vec.leak();
         unsafe { from_utf8_unchecked_mut(slice) }
     }
@@ -2247,8 +2247,7 @@ impl_eq! { Cow<'a, str>, &'b str }
 impl_eq! { Cow<'a, str>, String }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl const Default for String {
+impl Default for String {
     /// Creates an empty `String`.
     #[inline]
     fn default() -> String {
@@ -2528,6 +2527,15 @@ impl<T: fmt::Display + ?Sized> ToString for T {
 }
 
 #[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "ascii_char", issue = "110998")]
+impl ToString for core::ascii::Char {
+    #[inline]
+    fn to_string(&self) -> String {
+        self.as_str().to_owned()
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
 #[stable(feature = "char_to_string_specialization", since = "1.46.0")]
 impl ToString for char {
     #[inline]
@@ -2615,6 +2623,15 @@ impl ToString for String {
     }
 }
 
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "fmt_arguments_to_string_specialization", since = "1.71.0")]
+impl ToString for fmt::Arguments<'_> {
+    #[inline]
+    fn to_string(&self) -> String {
+        crate::fmt::format(*self)
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl AsRef<str> for String {
     #[inline]
@@ -2733,7 +2750,7 @@ impl<'a> From<Cow<'a, str>> for String {
     /// ```
     /// # use std::borrow::Cow;
     /// // If the string is not owned...
-    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
     /// // It will allocate on the heap and copy the string.
     /// let owned: String = String::from(cow);
     /// assert_eq!(&owned[..], "eggplant");
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 24849d52d..bfdb7a92b 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -502,6 +502,7 @@ impl<T> Arc<T> {
     /// assert_eq!(*five, 5)
     /// ```
     #[cfg(not(no_global_oom_handling))]
+    #[inline]
     #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
     pub fn new_uninit() -> Arc<mem::MaybeUninit<T>> {
@@ -535,6 +536,7 @@ impl<T> Arc<T> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
+    #[inline]
     #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
     pub fn new_zeroed() -> Arc<mem::MaybeUninit<T>> {
@@ -844,6 +846,7 @@ impl<T> Arc<[T]> {
     /// assert_eq!(*values, [1, 2, 3])
     /// ```
     #[cfg(not(no_global_oom_handling))]
+    #[inline]
     #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
     pub fn new_uninit_slice(len: usize) -> Arc<[mem::MaybeUninit<T>]> {
@@ -871,6 +874,7 @@ impl<T> Arc<[T]> {
     ///
     /// [zeroed]: mem::MaybeUninit::zeroed
     #[cfg(not(no_global_oom_handling))]
+    #[inline]
     #[unstable(feature = "new_uninit", issue = "63291")]
     #[must_use]
     pub fn new_zeroed_slice(len: usize) -> Arc<[mem::MaybeUninit<T>]> {
@@ -1300,10 +1304,10 @@ impl<T: ?Sized> Arc<T> {
         mem_to_arcinner: impl FnOnce(*mut u8) -> *mut ArcInner<T>,
     ) -> *mut ArcInner<T> {
         let layout = arcinner_layout_for_value_layout(value_layout);
-        unsafe {
-            Arc::try_allocate_for_layout(value_layout, allocate, mem_to_arcinner)
-                .unwrap_or_else(|_| handle_alloc_error(layout))
-        }
+
+        let ptr = allocate(layout).unwrap_or_else(|_| handle_alloc_error(layout));
+
+        unsafe { Self::initialize_arcinner(ptr, layout, mem_to_arcinner) }
     }
 
     /// Allocates an `ArcInner<T>` with sufficient space for
@@ -1321,7 +1325,16 @@ impl<T: ?Sized> Arc<T> {
 
         let ptr = allocate(layout)?;
 
-        // Initialize the ArcInner
+        let inner = unsafe { Self::initialize_arcinner(ptr, layout, mem_to_arcinner) };
+
+        Ok(inner)
+    }
+
+    unsafe fn initialize_arcinner(
+        ptr: NonNull<[u8]>,
+        layout: Layout,
+        mem_to_arcinner: impl FnOnce(*mut u8) -> *mut ArcInner<T>,
+    ) -> *mut ArcInner<T> {
         let inner = mem_to_arcinner(ptr.as_non_null_ptr().as_ptr());
         debug_assert_eq!(unsafe { Layout::for_value(&*inner) }, layout);
 
@@ -1330,7 +1343,7 @@ impl<T: ?Sized> Arc<T> {
             ptr::write(&mut (*inner).weak, atomic::AtomicUsize::new(1));
         }
 
-        Ok(inner)
+        inner
     }
 
     /// Allocates an `ArcInner<T>` with sufficient space for an unsized inner value.
@@ -2768,7 +2781,7 @@ where
     /// ```rust
     /// # use std::sync::Arc;
     /// # use std::borrow::Cow;
-    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
     /// let shared: Arc<str> = Arc::from(cow);
     /// assert_eq!("eggplant", &shared[..]);
     /// ```
diff --git a/library/alloc/src/task.rs b/library/alloc/src/task.rs
index 9d8e309a9..5d9772b87 100644
--- a/library/alloc/src/task.rs
+++ b/library/alloc/src/task.rs
@@ -39,6 +39,7 @@ use crate::sync::Arc;
 /// use std::sync::Arc;
 /// use std::task::{Context, Poll, Wake};
 /// use std::thread::{self, Thread};
+/// use core::pin::pin;
 ///
 /// /// A waker that wakes up the current thread when called.
 /// struct ThreadWaker(Thread);
@@ -52,7 +53,7 @@ use crate::sync::Arc;
 /// /// Run a future to completion on the current thread.
 /// fn block_on<T>(fut: impl Future<Output = T>) -> T {
 ///     // Pin the future so it can be polled.
-///     let mut fut = Box::pin(fut);
+///     let mut fut = pin!(fut);
 ///
 ///     // Create a new context to be passed to the future.
 ///     let t = thread::current();
diff --git a/library/alloc/src/vec/drain.rs b/library/alloc/src/vec/drain.rs
index 2b1a787cc..f0b63759a 100644
--- a/library/alloc/src/vec/drain.rs
+++ b/library/alloc/src/vec/drain.rs
@@ -16,7 +16,7 @@ use super::Vec;
 ///
 /// ```
 /// let mut v = vec![0, 1, 2];
-/// let iter: std::vec::Drain<_> = v.drain(..);
+/// let iter: std::vec::Drain<'_, _> = v.drain(..);
 /// ```
 #[stable(feature = "drain", since = "1.6.0")]
 pub struct Drain<
@@ -112,9 +112,7 @@ impl<'a, T, A: Allocator> Drain<'a, T, A> {
             let unyielded_ptr = this.iter.as_slice().as_ptr();
 
             // ZSTs have no identity, so we don't need to move them around.
-            let needs_move = mem::size_of::<T>() != 0;
-
-            if needs_move {
+            if !T::IS_ZST {
                 let start_ptr = source_vec.as_mut_ptr().add(start);
 
                 // memmove back unyielded elements
@@ -197,7 +195,7 @@ impl<T, A: Allocator> Drop for Drain<'_, T, A> {
             }
         }
 
-        let iter = mem::replace(&mut self.iter, (&mut []).iter());
+        let iter = mem::take(&mut self.iter);
         let drop_len = iter.len();
 
         let mut vec = self.vec;
diff --git a/library/alloc/src/vec/drain_filter.rs b/library/alloc/src/vec/drain_filter.rs
index 8c03f1692..21b090234 100644
--- a/library/alloc/src/vec/drain_filter.rs
+++ b/library/alloc/src/vec/drain_filter.rs
@@ -1,5 +1,5 @@
 use crate::alloc::{Allocator, Global};
-use core::mem::{self, ManuallyDrop};
+use core::mem::{ManuallyDrop, SizedTypeProperties};
 use core::ptr;
 use core::slice;
 
@@ -16,7 +16,7 @@ use super::Vec;
 /// #![feature(drain_filter)]
 ///
 /// let mut v = vec![0, 1, 2];
-/// let iter: std::vec::DrainFilter<_, _> = v.drain_filter(|x| *x % 2 == 0);
+/// let iter: std::vec::DrainFilter<'_, _, _> = v.drain_filter(|x| *x % 2 == 0);
 /// ```
 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
 #[derive(Debug)]
@@ -96,9 +96,7 @@ where
 
         unsafe {
             // ZSTs have no identity, so we don't need to move them around.
-            let needs_move = mem::size_of::<T>() != 0;
-
-            if needs_move && this.idx < this.old_len && this.del > 0 {
+            if !T::IS_ZST && this.idx < this.old_len && this.del > 0 {
                 let ptr = this.vec.as_mut_ptr();
                 let src = ptr.add(this.idx);
                 let dst = src.sub(this.del);
diff --git a/library/alloc/src/vec/in_place_collect.rs b/library/alloc/src/vec/in_place_collect.rs
index 87d61deb1..5ecd04799 100644
--- a/library/alloc/src/vec/in_place_collect.rs
+++ b/library/alloc/src/vec/in_place_collect.rs
@@ -178,7 +178,8 @@ where
             )
         };
 
-        let len = SpecInPlaceCollect::collect_in_place(&mut iterator, dst_buf, dst_end);
+        // SAFETY: `dst_buf` and `dst_end` are the start and end of the buffer.
+        let len = unsafe { SpecInPlaceCollect::collect_in_place(&mut iterator, dst_buf, dst_end) };
 
         let src = unsafe { iterator.as_inner().as_into_iter() };
         // check if SourceIter contract was upheld
@@ -201,7 +202,7 @@ where
         //
         // Note: This access to the source wouldn't be allowed by the TrustedRandomIteratorNoCoerce
         // contract (used by SpecInPlaceCollect below). But see the "O(1) collect" section in the
-        // module documenttation why this is ok anyway.
+        // module documentation why this is ok anyway.
         let dst_guard = InPlaceDstBufDrop { ptr: dst_buf, len, cap };
         src.forget_allocation_drop_remaining();
         mem::forget(dst_guard);
@@ -239,7 +240,7 @@ trait SpecInPlaceCollect<T, I>: Iterator<Item = T> {
     /// `Iterator::__iterator_get_unchecked` calls with a `TrustedRandomAccessNoCoerce` bound
     /// on `I` which means the caller of this method must take the safety conditions
     /// of that trait into consideration.
-    fn collect_in_place(&mut self, dst: *mut T, end: *const T) -> usize;
+    unsafe fn collect_in_place(&mut self, dst: *mut T, end: *const T) -> usize;
 }
 
 impl<T, I> SpecInPlaceCollect<T, I> for I
@@ -247,7 +248,7 @@ where
     I: Iterator<Item = T>,
 {
     #[inline]
-    default fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
+    default unsafe fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
         // use try-fold since
         // - it vectorizes better for some iterator adapters
         // - unlike most internal iteration methods, it only takes a &mut self
@@ -265,7 +266,7 @@ where
     I: Iterator<Item = T> + TrustedRandomAccessNoCoerce,
 {
     #[inline]
-    fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
+    unsafe fn collect_in_place(&mut self, dst_buf: *mut T, end: *const T) -> usize {
         let len = self.size();
         let mut drop_guard = InPlaceDrop { inner: dst_buf, dst: dst_buf };
         for i in 0..len {
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 3736a6e0b..47661a3d3 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -646,14 +646,14 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// // The vector contains no items, even though it has capacity for more
     /// assert_eq!(vec.len(), 0);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     ///
     /// // These are all done without reallocating...
     /// for i in 0..10 {
     ///     vec.push(i);
     /// }
     /// assert_eq!(vec.len(), 10);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     ///
     /// // ...but this may make the vector reallocate
     /// vec.push(11);
@@ -877,7 +877,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     /// let mut vec: Vec<i32> = Vec::with_capacity(10);
     /// vec.push(42);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -1028,7 +1028,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     /// let mut vec = Vec::with_capacity(10);
     /// vec.extend([1, 2, 3]);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// vec.shrink_to_fit();
     /// assert!(vec.capacity() >= 3);
     /// ```
@@ -1055,7 +1055,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     /// let mut vec = Vec::with_capacity(10);
     /// vec.extend([1, 2, 3]);
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// vec.shrink_to(4);
     /// assert!(vec.capacity() >= 4);
     /// vec.shrink_to(0);
@@ -1090,7 +1090,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// let mut vec = Vec::with_capacity(10);
     /// vec.extend([1, 2, 3]);
     ///
-    /// assert_eq!(vec.capacity(), 10);
+    /// assert!(vec.capacity() >= 10);
     /// let slice = vec.into_boxed_slice();
     /// assert_eq!(slice.into_vec().capacity(), 3);
     /// ```
@@ -2662,7 +2662,6 @@ impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
 /// as required by the `core::borrow::Borrow` implementation.
 ///
 /// ```
-/// #![feature(build_hasher_simple_hash_one)]
 /// use std::hash::BuildHasher;
 ///
 /// let b = std::collections::hash_map::RandomState::new();
@@ -3022,8 +3021,7 @@ unsafe impl<#[may_dangle] T, A: Allocator> Drop for Vec<T, A> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
-impl<T> const Default for Vec<T> {
+impl<T> Default for Vec<T> {
     /// Creates an empty `Vec<T>`.
     ///
     /// The vector will not allocate until elements are pushed onto it.
@@ -3143,8 +3141,8 @@ where
     ///
     /// ```
     /// # use std::borrow::Cow;
-    /// let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]);
-    /// let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]);
+    /// let o: Cow<'_, [i32]> = Cow::Owned(vec![1, 2, 3]);
+    /// let b: Cow<'_, [i32]> = Cow::Borrowed(&[1, 2, 3]);
     /// assert_eq!(Vec::from(o), Vec::from(b));
     /// ```
     fn from(s: Cow<'a, [T]>) -> Vec<T> {
diff --git a/library/alloc/src/vec/splice.rs b/library/alloc/src/vec/splice.rs
index 1861147fe..852fdcc3f 100644
--- a/library/alloc/src/vec/splice.rs
+++ b/library/alloc/src/vec/splice.rs
@@ -14,7 +14,7 @@ use super::{Drain, Vec};
 /// ```
 /// let mut v = vec![0, 1, 2];
 /// let new = [7, 8];
-/// let iter: std::vec::Splice<_> = v.splice(1.., new);
+/// let iter: std::vec::Splice<'_, _> = v.splice(1.., new);
 /// ```
 #[derive(Debug)]
 #[stable(feature = "vec_splice", since = "1.21.0")]