diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 4ce76409c6f19..744c7a541a53c 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -1424,28 +1424,33 @@ pub struct EarlyBoundRegion {
     pub name: Symbol,
 }
 
+/// A **ty**pe **v**ariable **ID**.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 pub struct TyVid {
     pub index: u32,
 }
 
+/// A **`const`** **v**ariable **ID**.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 pub struct ConstVid<'tcx> {
     pub index: u32,
     pub phantom: PhantomData<&'tcx ()>,
 }
 
+/// An **int**egral (`u32`, `i32`, `usize`, etc.) type **v**ariable **ID**.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 pub struct IntVid {
     pub index: u32,
 }
 
+/// An **float**ing-point (`f32` or `f64`) type **v**ariable **ID**.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 pub struct FloatVid {
     pub index: u32,
 }
 
 rustc_index::newtype_index! {
+    /// A **region** (lifetime) **v**ariable **ID**.
     pub struct RegionVid {
         DEBUG_FORMAT = custom,
     }
@@ -1457,18 +1462,40 @@ impl Atom for RegionVid {
     }
 }
 
+/// A placeholder for a type that hasn't been inferred yet.
+///
+/// E.g., if we have an empty array (`[]`), then we create a fresh
+/// type variable for the element type since we won't know until it's
+/// used what the element type is supposed to be.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub enum InferTy {
+    /// A type variable.
     TyVar(TyVid),
+    /// An integral type variable (`{integer}`).
+    ///
+    /// These are created when the compiler sees an integer literal like
+    /// `1` that could be several different types (`u8`, `i32`, `u32`, etc.).
+    /// We don't know until it's used what type it's supposed to be, so
+    /// we create a fresh type variable.
     IntVar(IntVid),
+    /// A floating-point type variable (`{float}`).
+    ///
+    /// These are created when the compiler sees an float literal like
+    /// `1.0` that could be either an `f32` or an `f64`.
+    /// We don't know until it's used what type it's supposed to be, so
+    /// we create a fresh type variable.
     FloatVar(FloatVid),
 
-    /// A `FreshTy` is one that is generated as a replacement for an
-    /// unbound type variable. This is convenient for caching etc. See
-    /// `infer::freshen` for more details.
+    /// A [`FreshTy`][Self::FreshTy] is one that is generated as a replacement
+    /// for an unbound type variable. This is convenient for caching etc. See
+    /// `rustc_infer::infer::freshen` for more details.
+    ///
+    /// Compare with [`TyVar`][Self::TyVar].
     FreshTy(u32),
+    /// Like [`FreshTy`][Self::FreshTy], but as a replacement for [`IntVar`][Self::IntVar].
     FreshIntTy(u32),
+    /// Like [`FreshTy`][Self::FreshTy], but as a replacement for [`FloatVar`][Self::FloatVar].
     FreshFloatTy(u32),
 }
 
diff --git a/compiler/rustc_traits/src/chalk/mod.rs b/compiler/rustc_traits/src/chalk/mod.rs
index f3a55fec9e462..bd2f87f70a2f1 100644
--- a/compiler/rustc_traits/src/chalk/mod.rs
+++ b/compiler/rustc_traits/src/chalk/mod.rs
@@ -98,7 +98,7 @@ crate fn evaluate_goal<'tcx>(
     let mut solver = chalk_engine::solve::SLGSolver::new(32, None);
     let db = ChalkRustIrDatabase { interner, reempty_placeholder };
     let solution = solver.solve(&db, &lowered_goal);
-    debug!(?obligation, ?solution, "evaluatate goal");
+    debug!(?obligation, ?solution, "evaluate goal");
 
     // Ideally, the code to convert *back* to rustc types would live close to
     // the code to convert *from* rustc types. Right now though, we don't
diff --git a/library/alloc/src/collections/binary_heap.rs b/library/alloc/src/collections/binary_heap.rs
index 97ebc12175f73..76051d9e1dffd 100644
--- a/library/alloc/src/collections/binary_heap.rs
+++ b/library/alloc/src/collections/binary_heap.rs
@@ -915,6 +915,7 @@ impl<T> BinaryHeap<T> {
     ///
     /// assert_eq!(heap.len(), 2);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> usize {
         self.data.len()
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 735213363f60d..944e0e65cf7c1 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -2132,6 +2132,7 @@ impl<K, V> BTreeMap<K, V> {
     /// a.insert(1, "a");
     /// assert_eq!(a.len(), 1);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
     pub const fn len(&self) -> usize {
diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs
index 16b4b1091eff7..b3641a7a0c697 100644
--- a/library/alloc/src/collections/btree/node.rs
+++ b/library/alloc/src/collections/btree/node.rs
@@ -489,7 +489,7 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
     ///
     /// # Safety
     /// `index` is in bounds of 0..CAPACITY
-    unsafe fn key_area_mut_at<I, Output: ?Sized>(&mut self, index: I) -> &mut Output
+    unsafe fn key_area_mut<I, Output: ?Sized>(&mut self, index: I) -> &mut Output
     where
         I: SliceIndex<[MaybeUninit<K>], Output = Output>,
     {
@@ -503,7 +503,7 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
     ///
     /// # Safety
     /// `index` is in bounds of 0..CAPACITY
-    unsafe fn val_area_mut_at<I, Output: ?Sized>(&mut self, index: I) -> &mut Output
+    unsafe fn val_area_mut<I, Output: ?Sized>(&mut self, index: I) -> &mut Output
     where
         I: SliceIndex<[MaybeUninit<V>], Output = Output>,
     {
@@ -519,7 +519,7 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
     ///
     /// # Safety
     /// `index` is in bounds of 0..CAPACITY + 1
-    unsafe fn edge_area_mut_at<I, Output: ?Sized>(&mut self, index: I) -> &mut Output
+    unsafe fn edge_area_mut<I, Output: ?Sized>(&mut self, index: I) -> &mut Output
     where
         I: SliceIndex<[MaybeUninit<BoxedNode<K, V>>], Output = Output>,
     {
@@ -583,8 +583,8 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
         assert!(idx < CAPACITY);
         *len += 1;
         unsafe {
-            self.key_area_mut_at(idx).write(key);
-            self.val_area_mut_at(idx).write(val);
+            self.key_area_mut(idx).write(key);
+            self.val_area_mut(idx).write(val);
         }
     }
 
@@ -593,8 +593,8 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
         let new_len = self.len() + 1;
         assert!(new_len <= CAPACITY);
         unsafe {
-            slice_insert(self.key_area_mut_at(..new_len), 0, key);
-            slice_insert(self.val_area_mut_at(..new_len), 0, val);
+            slice_insert(self.key_area_mut(..new_len), 0, key);
+            slice_insert(self.val_area_mut(..new_len), 0, val);
             *self.len_mut() = new_len as u16;
         }
     }
@@ -627,9 +627,9 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
         assert!(idx < CAPACITY);
         *len += 1;
         unsafe {
-            self.key_area_mut_at(idx).write(key);
-            self.val_area_mut_at(idx).write(val);
-            self.edge_area_mut_at(idx + 1).write(edge.node);
+            self.key_area_mut(idx).write(key);
+            self.val_area_mut(idx).write(val);
+            self.edge_area_mut(idx + 1).write(edge.node);
             Handle::new_edge(self.reborrow_mut(), idx + 1).correct_parent_link();
         }
     }
@@ -642,9 +642,9 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
         assert!(new_len <= CAPACITY);
 
         unsafe {
-            slice_insert(self.key_area_mut_at(..new_len), 0, key);
-            slice_insert(self.val_area_mut_at(..new_len), 0, val);
-            slice_insert(self.edge_area_mut_at(..new_len + 1), 0, edge.node);
+            slice_insert(self.key_area_mut(..new_len), 0, key);
+            slice_insert(self.val_area_mut(..new_len), 0, val);
+            slice_insert(self.edge_area_mut(..new_len + 1), 0, edge.node);
             *self.len_mut() = new_len as u16;
         }
 
@@ -662,12 +662,12 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
         let idx = self.len() - 1;
 
         unsafe {
-            let key = self.key_area_mut_at(idx).assume_init_read();
-            let val = self.val_area_mut_at(idx).assume_init_read();
+            let key = self.key_area_mut(idx).assume_init_read();
+            let val = self.val_area_mut(idx).assume_init_read();
             let edge = match self.reborrow_mut().force() {
                 ForceResult::Leaf(_) => None,
                 ForceResult::Internal(mut internal) => {
-                    let node = internal.edge_area_mut_at(idx + 1).assume_init_read();
+                    let node = internal.edge_area_mut(idx + 1).assume_init_read();
                     let mut edge = Root { node, height: internal.height - 1, _marker: PhantomData };
                     // Currently, clearing the parent link is superfluous, because we will
                     // insert the node elsewhere and set its parent link again.
@@ -690,12 +690,12 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
         let old_len = self.len();
 
         unsafe {
-            let key = slice_remove(self.key_area_mut_at(..old_len), 0);
-            let val = slice_remove(self.val_area_mut_at(..old_len), 0);
+            let key = slice_remove(self.key_area_mut(..old_len), 0);
+            let val = slice_remove(self.val_area_mut(..old_len), 0);
             let edge = match self.reborrow_mut().force() {
                 ForceResult::Leaf(_) => None,
                 ForceResult::Internal(mut internal) => {
-                    let node = slice_remove(internal.edge_area_mut_at(..old_len + 1), 0);
+                    let node = slice_remove(internal.edge_area_mut(..old_len + 1), 0);
                     let mut edge = Root { node, height: internal.height - 1, _marker: PhantomData };
                     // Currently, clearing the parent link is superfluous, because we will
                     // insert the node elsewhere and set its parent link again.
@@ -919,11 +919,11 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
         let new_len = self.node.len() + 1;
 
         unsafe {
-            slice_insert(self.node.key_area_mut_at(..new_len), self.idx, key);
-            slice_insert(self.node.val_area_mut_at(..new_len), self.idx, val);
+            slice_insert(self.node.key_area_mut(..new_len), self.idx, key);
+            slice_insert(self.node.val_area_mut(..new_len), self.idx, val);
             *self.node.len_mut() = new_len as u16;
 
-            self.node.val_area_mut_at(self.idx).assume_init_mut()
+            self.node.val_area_mut(self.idx).assume_init_mut()
         }
     }
 }
@@ -978,9 +978,9 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
         let new_len = self.node.len() + 1;
 
         unsafe {
-            slice_insert(self.node.key_area_mut_at(..new_len), self.idx, key);
-            slice_insert(self.node.val_area_mut_at(..new_len), self.idx, val);
-            slice_insert(self.node.edge_area_mut_at(..new_len + 1), self.idx + 1, edge.node);
+            slice_insert(self.node.key_area_mut(..new_len), self.idx, key);
+            slice_insert(self.node.val_area_mut(..new_len), self.idx, val);
+            slice_insert(self.node.edge_area_mut(..new_len + 1), self.idx + 1, edge.node);
             *self.node.len_mut() = new_len as u16;
 
             self.node.correct_childrens_parent_links(self.idx + 1..new_len + 1);
@@ -1085,7 +1085,7 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Immut<'a>, K, V, NodeTyp
 
 impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>, marker::KV> {
     pub fn key_mut(&mut self) -> &mut K {
-        unsafe { self.node.key_area_mut_at(self.idx).assume_init_mut() }
+        unsafe { self.node.key_area_mut(self.idx).assume_init_mut() }
     }
 
     pub fn into_val_mut(self) -> &'a mut V {
@@ -1127,16 +1127,16 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>
         let new_len = self.node.len() - self.idx - 1;
         new_node.len = new_len as u16;
         unsafe {
-            let k = self.node.key_area_mut_at(self.idx).assume_init_read();
-            let v = self.node.val_area_mut_at(self.idx).assume_init_read();
+            let k = self.node.key_area_mut(self.idx).assume_init_read();
+            let v = self.node.val_area_mut(self.idx).assume_init_read();
 
             ptr::copy_nonoverlapping(
-                self.node.key_area_mut_at(self.idx + 1..).as_ptr(),
+                self.node.key_area_mut(self.idx + 1..).as_ptr(),
                 new_node.keys.as_mut_ptr(),
                 new_len,
             );
             ptr::copy_nonoverlapping(
-                self.node.val_area_mut_at(self.idx + 1..).as_ptr(),
+                self.node.val_area_mut(self.idx + 1..).as_ptr(),
                 new_node.vals.as_mut_ptr(),
                 new_len,
             );
@@ -1173,8 +1173,8 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
     ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) {
         let old_len = self.node.len();
         unsafe {
-            let k = slice_remove(self.node.key_area_mut_at(..old_len), self.idx);
-            let v = slice_remove(self.node.val_area_mut_at(..old_len), self.idx);
+            let k = slice_remove(self.node.key_area_mut(..old_len), self.idx);
+            let v = slice_remove(self.node.val_area_mut(..old_len), self.idx);
             *self.node.len_mut() = (old_len - 1) as u16;
             ((k, v), self.left_edge())
         }
@@ -1195,7 +1195,7 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
             let kv = self.split_leaf_data(&mut new_node.data);
             let new_len = usize::from(new_node.data.len);
             ptr::copy_nonoverlapping(
-                self.node.edge_area_mut_at(self.idx + 1..).as_ptr(),
+                self.node.edge_area_mut(self.idx + 1..).as_ptr(),
                 new_node.edges.as_mut_ptr(),
                 new_len + 1,
             );
@@ -1321,25 +1321,23 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
         unsafe {
             *left_node.len_mut() = new_left_len as u16;
 
-            let parent_key =
-                slice_remove(parent_node.key_area_mut_at(..old_parent_len), parent_idx);
-            left_node.key_area_mut_at(old_left_len).write(parent_key);
+            let parent_key = slice_remove(parent_node.key_area_mut(..old_parent_len), parent_idx);
+            left_node.key_area_mut(old_left_len).write(parent_key);
             ptr::copy_nonoverlapping(
-                right_node.key_area_mut_at(..).as_ptr(),
-                left_node.key_area_mut_at(old_left_len + 1..).as_mut_ptr(),
+                right_node.key_area_mut(..).as_ptr(),
+                left_node.key_area_mut(old_left_len + 1..).as_mut_ptr(),
                 right_len,
             );
 
-            let parent_val =
-                slice_remove(parent_node.val_area_mut_at(..old_parent_len), parent_idx);
-            left_node.val_area_mut_at(old_left_len).write(parent_val);
+            let parent_val = slice_remove(parent_node.val_area_mut(..old_parent_len), parent_idx);
+            left_node.val_area_mut(old_left_len).write(parent_val);
             ptr::copy_nonoverlapping(
-                right_node.val_area_mut_at(..).as_ptr(),
-                left_node.val_area_mut_at(old_left_len + 1..).as_mut_ptr(),
+                right_node.val_area_mut(..).as_ptr(),
+                left_node.val_area_mut(old_left_len + 1..).as_mut_ptr(),
                 right_len,
             );
 
-            slice_remove(&mut parent_node.edge_area_mut_at(..old_parent_len + 1), parent_idx + 1);
+            slice_remove(&mut parent_node.edge_area_mut(..old_parent_len + 1), parent_idx + 1);
             parent_node.correct_childrens_parent_links(parent_idx + 1..old_parent_len);
             *parent_node.len_mut() -= 1;
 
@@ -1349,8 +1347,8 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
                 let mut left_node = left_node.reborrow_mut().cast_to_internal_unchecked();
                 let mut right_node = right_node.cast_to_internal_unchecked();
                 ptr::copy_nonoverlapping(
-                    right_node.edge_area_mut_at(..).as_ptr(),
-                    left_node.edge_area_mut_at(old_left_len + 1..).as_mut_ptr(),
+                    right_node.edge_area_mut(..).as_ptr(),
+                    left_node.edge_area_mut(old_left_len + 1..).as_mut_ptr(),
                     right_len + 1,
                 );
 
@@ -1458,7 +1456,7 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
             match (left_node.reborrow_mut().force(), right_node.reborrow_mut().force()) {
                 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
                     // Make room for stolen edges.
-                    let right_edges = right.edge_area_mut_at(..).as_mut_ptr();
+                    let right_edges = right.edge_area_mut(..).as_mut_ptr();
                     ptr::copy(right_edges, right_edges.add(count), old_right_len + 1);
                     right.correct_childrens_parent_links(count..new_right_len + 1);
 
@@ -1518,7 +1516,7 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
                     move_edges(right.reborrow_mut(), 0, left, old_left_len + 1, count);
 
                     // Fill gap where stolen edges used to be.
-                    let right_edges = right.edge_area_mut_at(..).as_mut_ptr();
+                    let right_edges = right.edge_area_mut(..).as_mut_ptr();
                     ptr::copy(right_edges.add(count), right_edges, new_right_len + 1);
                     right.correct_childrens_parent_links(0..=new_right_len);
                 }
@@ -1551,8 +1549,8 @@ unsafe fn move_edges<'a, K: 'a, V: 'a>(
     count: usize,
 ) {
     unsafe {
-        let source_ptr = source.edge_area_mut_at(..).as_ptr();
-        let dest_ptr = dest.edge_area_mut_at(dest_offset..).as_mut_ptr();
+        let source_ptr = source.edge_area_mut(..).as_ptr();
+        let dest_ptr = dest.edge_area_mut(dest_offset..).as_mut_ptr();
         ptr::copy_nonoverlapping(source_ptr.add(source_offset), dest_ptr, count);
         dest.correct_childrens_parent_links(dest_offset..dest_offset + count);
     }
diff --git a/library/alloc/src/collections/btree/set.rs b/library/alloc/src/collections/btree/set.rs
index f63c3dd580408..c72e305a1f947 100644
--- a/library/alloc/src/collections/btree/set.rs
+++ b/library/alloc/src/collections/btree/set.rs
@@ -975,6 +975,7 @@ impl<T> BTreeSet<T> {
     /// v.insert(1);
     /// assert_eq!(v.len(), 1);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
     pub const fn len(&self) -> usize {
diff --git a/library/alloc/src/collections/linked_list.rs b/library/alloc/src/collections/linked_list.rs
index 4707f12940171..397e774f1a03d 100644
--- a/library/alloc/src/collections/linked_list.rs
+++ b/library/alloc/src/collections/linked_list.rs
@@ -593,6 +593,7 @@ impl<T> LinkedList<T> {
     /// dl.push_back(3);
     /// assert_eq!(dl.len(), 3);
     /// ```
+    #[doc(alias = "length")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> usize {
diff --git a/library/alloc/src/collections/vec_deque/mod.rs b/library/alloc/src/collections/vec_deque/mod.rs
index 7cf4041f2920f..f8fad6de1a3cc 100644
--- a/library/alloc/src/collections/vec_deque/mod.rs
+++ b/library/alloc/src/collections/vec_deque/mod.rs
@@ -1038,6 +1038,7 @@ impl<T> VecDeque<T> {
     /// v.push_back(1);
     /// assert_eq!(v.len(), 1);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> usize {
         count(self.tail, self.head, self.cap())
@@ -1091,7 +1092,7 @@ impl<T> VecDeque<T> {
     /// assert_eq!(all.len(), 3);
     /// ```
     #[inline]
-    #[stable(feature = "deque_range", since = "1.50.0")]
+    #[stable(feature = "deque_range", since = "1.51.0")]
     pub fn range<R>(&self, range: R) -> Iter<'_, T>
     where
         R: RangeBounds<usize>,
@@ -1130,7 +1131,7 @@ impl<T> VecDeque<T> {
     /// assert_eq!(v, vec![2, 4, 12]);
     /// ```
     #[inline]
-    #[stable(feature = "deque_range", since = "1.50.0")]
+    #[stable(feature = "deque_range", since = "1.51.0")]
     pub fn range_mut<R>(&mut self, range: R) -> IterMut<'_, T>
     where
         R: RangeBounds<usize>,
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index 27b32b6950267..9198892859317 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -1388,6 +1388,7 @@ impl String {
     /// assert_eq!(fancy_f.len(), 4);
     /// assert_eq!(fancy_f.chars().count(), 3);
     /// ```
+    #[doc(alias = "length")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> usize {
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 53ba9c283ae23..7c03345aba507 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -14,7 +14,7 @@ use core::hint;
 use core::intrinsics::abort;
 use core::iter;
 use core::marker::{PhantomData, Unpin, Unsize};
-use core::mem::{self, align_of_val, size_of_val};
+use core::mem::{self, align_of_val_raw, size_of_val};
 use core::ops::{CoerceUnsized, Deref, DispatchFromDyn, Receiver};
 use core::pin::Pin;
 use core::ptr::{self, NonNull};
@@ -2366,7 +2366,7 @@ unsafe fn data_offset<T: ?Sized>(ptr: *const T) -> isize {
     // Because it is `?Sized`, it will always be the last field in memory.
     // Note: This is a detail of the current implementation of the compiler,
     // and is not a guaranteed language detail. Do not rely on it outside of std.
-    unsafe { data_offset_align(align_of_val(&*ptr)) }
+    unsafe { data_offset_align(align_of_val_raw(ptr)) }
 }
 
 #[inline]
diff --git a/library/alloc/src/vec.rs b/library/alloc/src/vec.rs
index 2b08f1f3629b3..c9fa41138cd41 100644
--- a/library/alloc/src/vec.rs
+++ b/library/alloc/src/vec.rs
@@ -1559,6 +1559,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// let a = vec![1, 2, 3];
     /// assert_eq!(a.len(), 3);
     /// ```
+    #[doc(alias = "length")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> usize {
diff --git a/library/core/src/char/convert.rs b/library/core/src/char/convert.rs
index 394db5b5917f0..de05a8c82e8f6 100644
--- a/library/core/src/char/convert.rs
+++ b/library/core/src/char/convert.rs
@@ -47,6 +47,7 @@ use super::MAX;
 ///
 /// assert_eq!(None, c);
 /// ```
+#[doc(alias = "chr")]
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn from_u32(i: u32) -> Option<char> {
diff --git a/library/core/src/iter/traits/exact_size.rs b/library/core/src/iter/traits/exact_size.rs
index eadbdf45c7c6f..996d62e2b4a42 100644
--- a/library/core/src/iter/traits/exact_size.rs
+++ b/library/core/src/iter/traits/exact_size.rs
@@ -91,6 +91,7 @@ pub trait ExactSizeIterator: Iterator {
     ///
     /// assert_eq!(5, five.len());
     /// ```
+    #[doc(alias = "length")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn len(&self) -> usize {
diff --git a/library/core/src/ptr/const_ptr.rs b/library/core/src/ptr/const_ptr.rs
index 8fd9ff768c4f4..38519f759ae05 100644
--- a/library/core/src/ptr/const_ptr.rs
+++ b/library/core/src/ptr/const_ptr.rs
@@ -232,23 +232,27 @@ impl<T: ?Sized> *const T {
     ///
     /// # Safety
     ///
-    /// The resulting pointer does not need to be in bounds, but it is
-    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// This operation itself is always safe, but using the resulting pointer is not.
     ///
-    /// In particular, the resulting pointer remains attached to the same allocated
-    /// object that `self` points to. It may *not* be used to access a
-    /// different allocated object. Note that in Rust,
-    /// every (stack-allocated) variable is considered a separate allocated object.
+    /// The resulting pointer remains attached to the same allocated object that `self` points to.
+    /// It may *not* be used to access a different allocated object. Note that in Rust, every
+    /// (stack-allocated) variable is considered a separate allocated object.
     ///
-    /// In other words, `x.wrapping_offset((y as usize).wrapping_sub(x as usize) / size_of::<T>())`
-    /// is *not* the same as `y`, and dereferencing it is undefined behavior
-    /// unless `x` and `y` point into the same allocated object.
+    /// In other words, `let z = x.wrapping_offset((y as isize) - (x as isize))` does *not* make `z`
+    /// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
+    /// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
+    /// `x` and `y` point into the same allocated object.
     ///
-    /// Compared to [`offset`], this method basically delays the requirement of staying
-    /// within the same allocated object: [`offset`] is immediate Undefined Behavior when
-    /// crossing object boundaries; `wrapping_offset` produces a pointer but still leads
-    /// to Undefined Behavior if that pointer is dereferenced. [`offset`] can be optimized
-    /// better and is thus preferable in performance-sensitive code.
+    /// Compared to [`offset`], this method basically delays the requirement of staying within the
+    /// same allocated object: [`offset`] is immediate Undefined Behavior when crossing object
+    /// boundaries; `wrapping_offset` produces a pointer but still leads to Undefined Behavior if a
+    /// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`offset`]
+    /// can be optimized better and is thus preferable in performance-sensitive code.
+    ///
+    /// The delayed check only considers the value of the pointer that was dereferenced, not the
+    /// intermediate values used during the computation of the final result. For example,
+    /// `x.wrapping_offset(o).wrapping_offset(o.wrapping_neg())` is always the same as `x`. In other
+    /// words, leaving the allocated object and then re-entering it later is permitted.
     ///
     /// If you need to cross object boundaries, cast the pointer to an integer and
     /// do the arithmetic there.
@@ -571,19 +575,27 @@ impl<T: ?Sized> *const T {
     ///
     /// # Safety
     ///
-    /// The resulting pointer does not need to be in bounds, but it is
-    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// This operation itself is always safe, but using the resulting pointer is not.
+    ///
+    /// The resulting pointer remains attached to the same allocated object that `self` points to.
+    /// It may *not* be used to access a different allocated object. Note that in Rust, every
+    /// (stack-allocated) variable is considered a separate allocated object.
+    ///
+    /// In other words, `let z = x.wrapping_add((y as usize) - (x as usize))` does *not* make `z`
+    /// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
+    /// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
+    /// `x` and `y` point into the same allocated object.
     ///
-    /// In particular, the resulting pointer remains attached to the same allocated
-    /// object that `self` points to. It may *not* be used to access a
-    /// different allocated object. Note that in Rust,
-    /// every (stack-allocated) variable is considered a separate allocated object.
+    /// Compared to [`add`], this method basically delays the requirement of staying within the
+    /// same allocated object: [`add`] is immediate Undefined Behavior when crossing object
+    /// boundaries; `wrapping_add` produces a pointer but still leads to Undefined Behavior if a
+    /// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`add`]
+    /// can be optimized better and is thus preferable in performance-sensitive code.
     ///
-    /// Compared to [`add`], this method basically delays the requirement of staying
-    /// within the same allocated object: [`add`] is immediate Undefined Behavior when
-    /// crossing object boundaries; `wrapping_add` produces a pointer but still leads
-    /// to Undefined Behavior if that pointer is dereferenced. [`add`] can be optimized
-    /// better and is thus preferable in performance-sensitive code.
+    /// The delayed check only considers the value of the pointer that was dereferenced, not the
+    /// intermediate values used during the computation of the final result. For example,
+    /// `x.wrapping_add(o).wrapping_sub(o)` is always the same as `x`. In other words, leaving the
+    /// allocated object and then re-entering it later is permitted.
     ///
     /// If you need to cross object boundaries, cast the pointer to an integer and
     /// do the arithmetic there.
@@ -628,19 +640,27 @@ impl<T: ?Sized> *const T {
     ///
     /// # Safety
     ///
-    /// The resulting pointer does not need to be in bounds, but it is
-    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// This operation itself is always safe, but using the resulting pointer is not.
+    ///
+    /// The resulting pointer remains attached to the same allocated object that `self` points to.
+    /// It may *not* be used to access a different allocated object. Note that in Rust, every
+    /// (stack-allocated) variable is considered a separate allocated object.
+    ///
+    /// In other words, `let z = x.wrapping_sub((x as usize) - (y as usize))` does *not* make `z`
+    /// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
+    /// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
+    /// `x` and `y` point into the same allocated object.
     ///
-    /// In particular, the resulting pointer remains attached to the same allocated
-    /// object that `self` points to. It may *not* be used to access a
-    /// different allocated object. Note that in Rust,
-    /// every (stack-allocated) variable is considered a separate allocated object.
+    /// Compared to [`sub`], this method basically delays the requirement of staying within the
+    /// same allocated object: [`sub`] is immediate Undefined Behavior when crossing object
+    /// boundaries; `wrapping_sub` produces a pointer but still leads to Undefined Behavior if a
+    /// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`sub`]
+    /// can be optimized better and is thus preferable in performance-sensitive code.
     ///
-    /// Compared to [`sub`], this method basically delays the requirement of staying
-    /// within the same allocated object: [`sub`] is immediate Undefined Behavior when
-    /// crossing object boundaries; `wrapping_sub` produces a pointer but still leads
-    /// to Undefined Behavior if that pointer is dereferenced. [`sub`] can be optimized
-    /// better and is thus preferable in performance-sensitive code.
+    /// The delayed check only considers the value of the pointer that was dereferenced, not the
+    /// intermediate values used during the computation of the final result. For example,
+    /// `x.wrapping_add(o).wrapping_sub(o)` is always the same as `x`. In other words, leaving the
+    /// allocated object and then re-entering it later is permitted.
     ///
     /// If you need to cross object boundaries, cast the pointer to an integer and
     /// do the arithmetic there.
diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index 5f94c2393aef3..92f4e431de499 100644
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -238,23 +238,27 @@ impl<T: ?Sized> *mut T {
     ///
     /// # Safety
     ///
-    /// The resulting pointer does not need to be in bounds, but it is
-    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// This operation itself is always safe, but using the resulting pointer is not.
     ///
-    /// In particular, the resulting pointer remains attached to the same allocated
-    /// object that `self` points to. It may *not* be used to access a
-    /// different allocated object. Note that in Rust,
-    /// every (stack-allocated) variable is considered a separate allocated object.
+    /// The resulting pointer remains attached to the same allocated object that `self` points to.
+    /// It may *not* be used to access a different allocated object. Note that in Rust, every
+    /// (stack-allocated) variable is considered a separate allocated object.
     ///
-    /// In other words, `x.wrapping_offset((y as usize).wrapping_sub(x as usize) / size_of::<T>())`
-    /// is *not* the same as `y`, and dereferencing it is undefined behavior
-    /// unless `x` and `y` point into the same allocated object.
+    /// In other words, `let z = x.wrapping_offset((y as isize) - (x as isize))` does *not* make `z`
+    /// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
+    /// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
+    /// `x` and `y` point into the same allocated object.
     ///
-    /// Compared to [`offset`], this method basically delays the requirement of staying
-    /// within the same allocated object: [`offset`] is immediate Undefined Behavior when
-    /// crossing object boundaries; `wrapping_offset` produces a pointer but still leads
-    /// to Undefined Behavior if that pointer is dereferenced. [`offset`] can be optimized
-    /// better and is thus preferable in performance-sensitive code.
+    /// Compared to [`offset`], this method basically delays the requirement of staying within the
+    /// same allocated object: [`offset`] is immediate Undefined Behavior when crossing object
+    /// boundaries; `wrapping_offset` produces a pointer but still leads to Undefined Behavior if a
+    /// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`offset`]
+    /// can be optimized better and is thus preferable in performance-sensitive code.
+    ///
+    /// The delayed check only considers the value of the pointer that was dereferenced, not the
+    /// intermediate values used during the computation of the final result. For example,
+    /// `x.wrapping_offset(o).wrapping_offset(o.wrapping_neg())` is always the same as `x`. In other
+    /// words, leaving the allocated object and then re-entering it later is permitted.
     ///
     /// If you need to cross object boundaries, cast the pointer to an integer and
     /// do the arithmetic there.
@@ -678,19 +682,27 @@ impl<T: ?Sized> *mut T {
     ///
     /// # Safety
     ///
-    /// The resulting pointer does not need to be in bounds, but it is
-    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// This operation itself is always safe, but using the resulting pointer is not.
+    ///
+    /// The resulting pointer remains attached to the same allocated object that `self` points to.
+    /// It may *not* be used to access a different allocated object. Note that in Rust, every
+    /// (stack-allocated) variable is considered a separate allocated object.
+    ///
+    /// In other words, `let z = x.wrapping_add((y as usize) - (x as usize))` does *not* make `z`
+    /// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
+    /// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
+    /// `x` and `y` point into the same allocated object.
     ///
-    /// In particular, the resulting pointer remains attached to the same allocated
-    /// object that `self` points to. It may *not* be used to access a
-    /// different allocated object. Note that in Rust,
-    /// every (stack-allocated) variable is considered a separate allocated object.
+    /// Compared to [`add`], this method basically delays the requirement of staying within the
+    /// same allocated object: [`add`] is immediate Undefined Behavior when crossing object
+    /// boundaries; `wrapping_add` produces a pointer but still leads to Undefined Behavior if a
+    /// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`add`]
+    /// can be optimized better and is thus preferable in performance-sensitive code.
     ///
-    /// Compared to [`add`], this method basically delays the requirement of staying
-    /// within the same allocated object: [`add`] is immediate Undefined Behavior when
-    /// crossing object boundaries; `wrapping_add` produces a pointer but still leads
-    /// to Undefined Behavior if that pointer is dereferenced. [`add`] can be optimized
-    /// better and is thus preferable in performance-sensitive code.
+    /// The delayed check only considers the value of the pointer that was dereferenced, not the
+    /// intermediate values used during the computation of the final result. For example,
+    /// `x.wrapping_add(o).wrapping_sub(o)` is always the same as `x`. In other words, leaving the
+    /// allocated object and then re-entering it later is permitted.
     ///
     /// If you need to cross object boundaries, cast the pointer to an integer and
     /// do the arithmetic there.
@@ -735,19 +747,27 @@ impl<T: ?Sized> *mut T {
     ///
     /// # Safety
     ///
-    /// The resulting pointer does not need to be in bounds, but it is
-    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// This operation itself is always safe, but using the resulting pointer is not.
+    ///
+    /// The resulting pointer remains attached to the same allocated object that `self` points to.
+    /// It may *not* be used to access a different allocated object. Note that in Rust, every
+    /// (stack-allocated) variable is considered a separate allocated object.
+    ///
+    /// In other words, `let z = x.wrapping_sub((x as usize) - (y as usize))` does *not* make `z`
+    /// the same as `y` even if we assume `T` has size `1` and there is no overflow: `z` is still
+    /// attached to the object `x` is attached to, and dereferencing it is Undefined Behavior unless
+    /// `x` and `y` point into the same allocated object.
     ///
-    /// In particular, the resulting pointer remains attached to the same allocated
-    /// object that `self` points to. It may *not* be used to access a
-    /// different allocated object. Note that in Rust,
-    /// every (stack-allocated) variable is considered a separate allocated object.
+    /// Compared to [`sub`], this method basically delays the requirement of staying within the
+    /// same allocated object: [`sub`] is immediate Undefined Behavior when crossing object
+    /// boundaries; `wrapping_sub` produces a pointer but still leads to Undefined Behavior if a
+    /// pointer is dereferenced when it is out-of-bounds of the object it is attached to. [`sub`]
+    /// can be optimized better and is thus preferable in performance-sensitive code.
     ///
-    /// Compared to [`sub`], this method basically delays the requirement of staying
-    /// within the same allocated object: [`sub`] is immediate Undefined Behavior when
-    /// crossing object boundaries; `wrapping_sub` produces a pointer but still leads
-    /// to Undefined Behavior if that pointer is dereferenced. [`sub`] can be optimized
-    /// better and is thus preferable in performance-sensitive code.
+    /// The delayed check only considers the value of the pointer that was dereferenced, not the
+    /// intermediate values used during the computation of the final result. For example,
+    /// `x.wrapping_add(o).wrapping_sub(o)` is always the same as `x`. In other words, leaving the
+    /// allocated object and then re-entering it later is permitted.
     ///
     /// If you need to cross object boundaries, cast the pointer to an integer and
     /// do the arithmetic there.
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index f5af48e0dd277..bb1014332a1cf 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -84,6 +84,7 @@ impl<T> [T] {
     /// let a = [1, 2, 3];
     /// assert_eq!(a.len(), 3);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_slice_len", since = "1.32.0")]
     #[inline]
diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs
index 83cf47c8c8f61..ba495a1a9fbe4 100644
--- a/library/core/src/str/mod.rs
+++ b/library/core/src/str/mod.rs
@@ -138,6 +138,7 @@ impl str {
     /// assert_eq!("ƒoo".len(), 4); // fancy f!
     /// assert_eq!("ƒoo".chars().count(), 3);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_str_len", since = "1.32.0")]
     #[inline]
diff --git a/library/std/src/collections/hash/map.rs b/library/std/src/collections/hash/map.rs
index 4f24a8bb75a0e..0680b1fc32975 100644
--- a/library/std/src/collections/hash/map.rs
+++ b/library/std/src/collections/hash/map.rs
@@ -448,6 +448,7 @@ impl<K, V, S> HashMap<K, V, S> {
     /// a.insert(1, "a");
     /// assert_eq!(a.len(), 1);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> usize {
         self.base.len()
diff --git a/library/std/src/collections/hash/set.rs b/library/std/src/collections/hash/set.rs
index 27093c1a077b0..f49e5801c3535 100644
--- a/library/std/src/collections/hash/set.rs
+++ b/library/std/src/collections/hash/set.rs
@@ -199,6 +199,7 @@ impl<T, S> HashSet<T, S> {
     /// v.insert(1);
     /// assert_eq!(v.len(), 1);
     /// ```
+    #[doc(alias = "length")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn len(&self) -> usize {
diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs
index 5d93016cadb37..2eef4d58507c0 100644
--- a/library/std/src/ffi/os_str.rs
+++ b/library/std/src/ffi/os_str.rs
@@ -653,6 +653,7 @@ impl OsStr {
     /// let os_str = OsStr::new("foo");
     /// assert_eq!(os_str.len(), 3);
     /// ```
+    #[doc(alias = "length")]
     #[stable(feature = "osstring_simple_functions", since = "1.9.0")]
     pub fn len(&self) -> usize {
         self.inner.inner.len()
diff --git a/src/doc/rustc/book.toml b/src/doc/rustc/book.toml
index 8adc05c513720..21d127c39c904 100644
--- a/src/doc/rustc/book.toml
+++ b/src/doc/rustc/book.toml
@@ -3,3 +3,6 @@ authors = ["The Rust Project Developers"]
 multilingual = false
 src = "src"
 title = "The rustc book"
+
+[output.html]
+git-repository-url = "https://github.com/rust-lang/rust/tree/master/src/doc/rustc"
diff --git a/src/doc/rustdoc/book.toml b/src/doc/rustdoc/book.toml
index ba30c107667ed..c2e7ff589066b 100644
--- a/src/doc/rustdoc/book.toml
+++ b/src/doc/rustdoc/book.toml
@@ -2,3 +2,6 @@
 authors = ["The Rust Project Developers"]
 src = "src"
 title = "The rustdoc book"
+
+[output.html]
+git-repository-url = "https://github.com/rust-lang/rust/tree/master/src/doc/rustdoc"
diff --git a/src/doc/rustdoc/src/what-is-rustdoc.md b/src/doc/rustdoc/src/what-is-rustdoc.md
index 1f6dced180b96..32dc1e02bb3db 100644
--- a/src/doc/rustdoc/src/what-is-rustdoc.md
+++ b/src/doc/rustdoc/src/what-is-rustdoc.md
@@ -10,7 +10,7 @@ CSS, and JavaScript.
 Let's give it a try! Create a new project with Cargo:
 
 ```bash
-$ cargo new docs
+$ cargo new docs --lib
 $ cd docs
 ```
 
diff --git a/src/test/ui/const-generics/issues/issue-80375.rs b/src/test/ui/const-generics/issues/issue-80375.rs
new file mode 100644
index 0000000000000..c906bb2c4d9b4
--- /dev/null
+++ b/src/test/ui/const-generics/issues/issue-80375.rs
@@ -0,0 +1,4 @@
+struct MyArray<const COUNT: usize>([u8; COUNT + 1]);
+//~^ ERROR generic parameters may not be used in const operations
+
+fn main() {}
diff --git a/src/test/ui/const-generics/issues/issue-80375.stderr b/src/test/ui/const-generics/issues/issue-80375.stderr
new file mode 100644
index 0000000000000..9765a639a48d0
--- /dev/null
+++ b/src/test/ui/const-generics/issues/issue-80375.stderr
@@ -0,0 +1,11 @@
+error: generic parameters may not be used in const operations
+  --> $DIR/issue-80375.rs:1:41
+   |
+LL | struct MyArray<const COUNT: usize>([u8; COUNT + 1]);
+   |                                         ^^^^^ cannot perform const operation using `COUNT`
+   |
+   = help: const parameters may only be used as standalone arguments, i.e. `COUNT`
+   = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions
+
+error: aborting due to previous error
+