diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index bd2ad257402..735213363f6 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -248,7 +248,7 @@ where
         let (map, dormant_map) = DormantMutRef::new(self);
         let root_node = Self::ensure_is_owned(&mut map.root).borrow_mut();
         match search::search_tree::<marker::Mut<'_>, K, (), K>(root_node, &key) {
-            Found(handle) => Some(mem::replace(handle.into_key_mut(), key)),
+            Found(mut kv) => Some(mem::replace(kv.key_mut(), key)),
             GoDown(handle) => {
                 VacantEntry { key, handle, dormant_map, _marker: PhantomData }.insert(());
                 None
diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs
index 22e179af4a9..a3ff83561f1 100644
--- a/library/alloc/src/collections/btree/node.rs
+++ b/library/alloc/src/collections/btree/node.rs
@@ -239,17 +239,16 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
 /// - We cannot get implicit coercion from say `Mut<'a>` to `Immut<'a>`.
 ///   Therefore, we have to explicitly call `reborrow` on a more powerfull
 ///   `NodeRef` in order to reach a method like `key_at`.
-/// - All methods on `NodeRef` that return some kind of reference, except
-///   `reborrow` and `reborrow_mut`, take `self` by value and not by reference.
-///   This avoids silently returning a second reference somewhere in the tree.
-///   That is irrelevant when `BorrowType` is `Immut<'a>`, but the rule does
-///   no harm because we make those `NodeRef` implicitly `Copy`.
-///   The rule also avoids implicitly returning the lifetime of `&self`,
-///   instead of the lifetime carried by `BorrowType`.
-///   An exception to this rule are the insert functions.
-/// - Given the above, we need a `reborrow_mut` to explicitly copy a `Mut<'a>`
-///   `NodeRef` whenever we want to invoke a method returning an extra reference
-///   somewhere in the tree.
+///
+/// All methods on `NodeRef` that return some kind of reference, either:
+/// - Take `self` by value, and return the lifetime carried by `BorrowType`.
+///   Sometimes, to invoke such a method, we need to call `reborrow_mut`.
+/// - Take `self` by reference, and (implicitly) return that reference's
+///   lifetime, instead of the lifetime carried by `BorrowType`. That way,
+///   the borrow checker guarantees that the `NodeRef` remains borrowed as long
+///   as the returned reference is used.
+///   The methods supporting insert bend this rule by returning a raw pointer,
+///   i.e., a reference without any lifetime.
 pub struct NodeRef<BorrowType, K, V, Type> {
     /// The number of levels that the node and the level of leaves are apart, a
     /// constant of the node that cannot be entirely described by `Type`, and that
@@ -305,9 +304,9 @@ impl<'a, K, V> NodeRef<marker::Immut<'a>, K, V, marker::Internal> {
 }
 
 impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
-    /// Offers exclusive access to the data of an internal node.
-    fn as_internal_mut(this: &mut Self) -> &'a mut InternalNode<K, V> {
-        let ptr = Self::as_internal_ptr(this);
+    /// Borrows exclusive access to the data of an internal node.
+    fn as_internal_mut(&mut self) -> &mut InternalNode<K, V> {
+        let ptr = Self::as_internal_ptr(self);
         unsafe { &mut *ptr }
     }
 }
@@ -355,7 +354,7 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
     /// The node has more than `idx` initialized elements.
     pub unsafe fn key_at(self, idx: usize) -> &'a K {
         debug_assert!(idx < self.len());
-        unsafe { Self::as_leaf(&self).keys.get_unchecked(idx).assume_init_ref() }
+        unsafe { self.into_leaf().keys.get_unchecked(idx).assume_init_ref() }
     }
 
     /// Exposes one of the values stored in the node.
@@ -364,7 +363,7 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
     /// The node has more than `idx` initialized elements.
     unsafe fn val_at(self, idx: usize) -> &'a V {
         debug_assert!(idx < self.len());
-        unsafe { Self::as_leaf(&self).vals.get_unchecked(idx).assume_init_ref() }
+        unsafe { self.into_leaf().vals.get_unchecked(idx).assume_init_ref() }
     }
 }
 
@@ -431,8 +430,8 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
 
 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
     /// Exposes the leaf portion of any leaf or internal node in an immutable tree.
-    fn as_leaf(this: &Self) -> &'a LeafNode<K, V> {
-        let ptr = Self::as_leaf_ptr(this);
+    fn into_leaf(self) -> &'a LeafNode<K, V> {
+        let ptr = Self::as_leaf_ptr(&self);
         // SAFETY: there can be no mutable references into this tree borrowed as `Immut`.
         unsafe { &*ptr }
     }
@@ -489,42 +488,49 @@ impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
         NodeRef { height: self.height, node: self.node, _marker: PhantomData }
     }
 
+    /// Borrows exclusive access to the leaf portion of any leaf or internal node.
+    fn as_leaf_mut(&mut self) -> &mut LeafNode<K, V> {
+        let ptr = Self::as_leaf_ptr(self);
+        // SAFETY: we have exclusive access to the entire node.
+        unsafe { &mut *ptr }
+    }
+
     /// Offers exclusive access to the leaf portion of any leaf or internal node.
-    fn as_leaf_mut(this: &mut Self) -> &'a mut LeafNode<K, V> {
-        let ptr = Self::as_leaf_ptr(this);
+    fn into_leaf_mut(mut self) -> &'a mut LeafNode<K, V> {
+        let ptr = Self::as_leaf_ptr(&mut self);
         // SAFETY: we have exclusive access to the entire node.
         unsafe { &mut *ptr }
     }
 }
 
 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
-    /// Offers exclusive access to a part of the key storage area.
+    /// Borrows exclusive access to an element of the key storage area.
     ///
     /// # Safety
     /// The node has more than `idx` initialized elements.
-    unsafe fn into_key_area_mut_at(mut self, idx: usize) -> &'a mut MaybeUninit<K> {
+    unsafe fn key_area_mut_at(&mut self, idx: usize) -> &mut MaybeUninit<K> {
         debug_assert!(idx < self.len());
-        unsafe { Self::as_leaf_mut(&mut self).keys.get_unchecked_mut(idx) }
+        unsafe { self.as_leaf_mut().keys.get_unchecked_mut(idx) }
     }
 
-    /// Offers exclusive access to a part of the value storage area.
+    /// Borrows exclusive access to an element of the value storage area.
     ///
     /// # Safety
     /// The node has more than `idx` initialized elements.
-    unsafe fn into_val_area_mut_at(mut self, idx: usize) -> &'a mut MaybeUninit<V> {
+    unsafe fn val_area_mut_at(&mut self, idx: usize) -> &mut MaybeUninit<V> {
         debug_assert!(idx < self.len());
-        unsafe { Self::as_leaf_mut(&mut self).vals.get_unchecked_mut(idx) }
+        unsafe { self.as_leaf_mut().vals.get_unchecked_mut(idx) }
     }
 }
 
 impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
-    /// Offers exclusive access to a part of the storage area for edge contents.
+    /// Borrows exclusive access to an element of the storage area for edge contents.
     ///
     /// # Safety
     /// The node has at least `idx` initialized elements.
-    unsafe fn into_edge_area_mut_at(mut self, idx: usize) -> &'a mut MaybeUninit<BoxedNode<K, V>> {
+    unsafe fn edge_area_mut_at(&mut self, idx: usize) -> &mut MaybeUninit<BoxedNode<K, V>> {
         debug_assert!(idx <= self.len());
-        unsafe { Self::as_internal_mut(&mut self).edges.get_unchecked_mut(idx) }
+        unsafe { self.as_internal_mut().edges.get_unchecked_mut(idx) }
     }
 }
 
@@ -533,14 +539,14 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
     /// regardless of the node's current length,
     /// having exclusive access to the entire node.
     unsafe fn key_area(self) -> &'a [MaybeUninit<K>] {
-        Self::as_leaf(&self).keys.as_slice()
+        self.into_leaf().keys.as_slice()
     }
 
     /// Exposes the entire value storage area in the node,
     /// regardless of the node's current length,
     /// having exclusive access to the entire node.
     unsafe fn val_area(self) -> &'a [MaybeUninit<V>] {
-        Self::as_leaf(&self).vals.as_slice()
+        self.into_leaf().vals.as_slice()
     }
 }
 
@@ -554,33 +560,33 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Immut<'a>, K, V, marker::Internal> {
 }
 
 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
-    /// Offers exclusive access to a sized slice of key storage area in the node.
-    unsafe fn into_key_area_slice(mut self) -> &'a mut [MaybeUninit<K>] {
+    /// Borrows exclusive access to a sized slice of key storage area in the node.
+    unsafe fn key_area_slice(&mut self) -> &mut [MaybeUninit<K>] {
         let len = self.len();
         // SAFETY: the caller will not be able to call further methods on self
         // until the key slice reference is dropped, as we have unique access
         // for the lifetime of the borrow.
-        unsafe { Self::as_leaf_mut(&mut self).keys.get_unchecked_mut(..len) }
+        unsafe { self.as_leaf_mut().keys.get_unchecked_mut(..len) }
     }
 
-    /// Offers exclusive access to a sized slice of value storage area in the node.
-    unsafe fn into_val_area_slice(mut self) -> &'a mut [MaybeUninit<V>] {
+    /// Borrows exclusive access to a sized slice of value storage area in the node.
+    unsafe fn val_area_slice(&mut self) -> &mut [MaybeUninit<V>] {
         let len = self.len();
         // SAFETY: the caller will not be able to call further methods on self
         // until the value slice reference is dropped, as we have unique access
         // for the lifetime of the borrow.
-        unsafe { Self::as_leaf_mut(&mut self).vals.get_unchecked_mut(..len) }
+        unsafe { self.as_leaf_mut().vals.get_unchecked_mut(..len) }
     }
 }
 
 impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
-    /// Offers exclusive access to a sized slice of storage area for edge contents in the node.
-    unsafe fn into_edge_area_slice(mut self) -> &'a mut [MaybeUninit<BoxedNode<K, V>>] {
+    /// Borrows exclusive access to a sized slice of storage area for edge contents in the node.
+    unsafe fn edge_area_slice(&mut self) -> &mut [MaybeUninit<BoxedNode<K, V>>] {
         let len = self.len();
         // SAFETY: the caller will not be able to call further methods on self
         // until the edge slice reference is dropped, as we have unique access
         // for the lifetime of the borrow.
-        unsafe { Self::as_internal_mut(&mut self).edges.get_unchecked_mut(..len + 1) }
+        unsafe { self.as_internal_mut().edges.get_unchecked_mut(..len + 1) }
     }
 }
 
@@ -604,9 +610,9 @@ impl<'a, K, V, Type> NodeRef<marker::ValMut<'a>, K, V, Type> {
 }
 
 impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
-    /// Exposes exclusive access to the length of the node.
-    pub fn into_len_mut(mut self) -> &'a mut u16 {
-        &mut (*Self::as_leaf_mut(&mut self)).len
+    /// Borrows exclusive access to the length of the node.
+    pub fn len_mut(&mut self) -> &mut u16 {
+        &mut self.as_leaf_mut().len
     }
 }
 
@@ -623,7 +629,8 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
 impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
     /// Clears the root's link to its parent edge.
     fn clear_parent_link(&mut self) {
-        let leaf = NodeRef::as_leaf_mut(&mut self.borrow_mut());
+        let mut root_node = self.borrow_mut();
+        let leaf = root_node.as_leaf_mut();
         leaf.parent = None;
     }
 }
@@ -631,13 +638,13 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
 impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
     /// Adds a key-value pair to the end of the node.
     pub fn push(&mut self, key: K, val: V) {
-        let len = unsafe { self.reborrow_mut().into_len_mut() };
+        let len = self.len_mut();
         let idx = usize::from(*len);
         assert!(idx < CAPACITY);
         *len += 1;
         unsafe {
-            self.reborrow_mut().into_key_area_mut_at(idx).write(key);
-            self.reborrow_mut().into_val_area_mut_at(idx).write(val);
+            self.key_area_mut_at(idx).write(key);
+            self.val_area_mut_at(idx).write(val);
         }
     }
 
@@ -646,9 +653,9 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Leaf> {
         assert!(self.len() < CAPACITY);
 
         unsafe {
-            *self.reborrow_mut().into_len_mut() += 1;
-            slice_insert(self.reborrow_mut().into_key_area_slice(), 0, key);
-            slice_insert(self.reborrow_mut().into_val_area_slice(), 0, val);
+            *self.len_mut() += 1;
+            slice_insert(self.key_area_slice(), 0, key);
+            slice_insert(self.val_area_slice(), 0, val);
         }
     }
 }
@@ -675,14 +682,14 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
     pub fn push(&mut self, key: K, val: V, edge: Root<K, V>) {
         assert!(edge.height == self.height - 1);
 
-        let len = unsafe { self.reborrow_mut().into_len_mut() };
+        let len = self.len_mut();
         let idx = usize::from(*len);
         assert!(idx < CAPACITY);
         *len += 1;
         unsafe {
-            self.reborrow_mut().into_key_area_mut_at(idx).write(key);
-            self.reborrow_mut().into_val_area_mut_at(idx).write(val);
-            self.reborrow_mut().into_edge_area_mut_at(idx + 1).write(edge.node);
+            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);
             Handle::new_edge(self.reborrow_mut(), idx + 1).correct_parent_link();
         }
     }
@@ -694,10 +701,10 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
         assert!(self.len() < CAPACITY);
 
         unsafe {
-            *self.reborrow_mut().into_len_mut() += 1;
-            slice_insert(self.reborrow_mut().into_key_area_slice(), 0, key);
-            slice_insert(self.reborrow_mut().into_val_area_slice(), 0, val);
-            slice_insert(self.reborrow_mut().into_edge_area_slice(), 0, edge.node);
+            *self.len_mut() += 1;
+            slice_insert(self.key_area_slice(), 0, key);
+            slice_insert(self.val_area_slice(), 0, val);
+            slice_insert(self.edge_area_slice(), 0, edge.node);
         }
 
         self.correct_all_childrens_parent_links();
@@ -728,7 +735,7 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
                 }
             };
 
-            *self.reborrow_mut().into_len_mut() -= 1;
+            *self.len_mut() -= 1;
             (key, val, edge)
         }
     }
@@ -742,12 +749,12 @@ 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.reborrow_mut().into_key_area_slice(), 0);
-            let val = slice_remove(self.reborrow_mut().into_val_area_slice(), 0);
+            let key = slice_remove(self.key_area_slice(), 0);
+            let val = slice_remove(self.val_area_slice(), 0);
             let edge = match self.reborrow_mut().force() {
                 ForceResult::Leaf(_) => None,
                 ForceResult::Internal(mut internal) => {
-                    let node = slice_remove(internal.reborrow_mut().into_edge_area_slice(), 0);
+                    let node = slice_remove(internal.edge_area_slice(), 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.
@@ -759,14 +766,14 @@ impl<'a, K: 'a, V: 'a> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
                 }
             };
 
-            *self.reborrow_mut().into_len_mut() -= 1;
+            *self.len_mut() -= 1;
 
             (key, val, edge)
         }
     }
 
     fn into_kv_pointers_mut(mut self) -> (*mut K, *mut V) {
-        let leaf = Self::as_leaf_mut(&mut self);
+        let leaf = self.as_leaf_mut();
         let keys = MaybeUninit::slice_as_mut_ptr(&mut leaf.keys);
         let vals = MaybeUninit::slice_as_mut_ptr(&mut leaf.vals);
         (keys, vals)
@@ -970,11 +977,11 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
         debug_assert!(self.node.len() < CAPACITY);
 
         unsafe {
-            *self.node.reborrow_mut().into_len_mut() += 1;
-            slice_insert(self.node.reborrow_mut().into_key_area_slice(), self.idx, key);
-            slice_insert(self.node.reborrow_mut().into_val_area_slice(), self.idx, val);
+            *self.node.len_mut() += 1;
+            slice_insert(self.node.key_area_slice(), self.idx, key);
+            slice_insert(self.node.val_area_slice(), self.idx, val);
 
-            self.node.reborrow_mut().into_val_area_mut_at(self.idx).assume_init_mut()
+            self.node.val_area_mut_at(self.idx).assume_init_mut()
         }
     }
 }
@@ -1028,10 +1035,10 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>,
         debug_assert!(edge.height == self.node.height - 1);
 
         unsafe {
-            *self.node.reborrow_mut().into_len_mut() += 1;
-            slice_insert(self.node.reborrow_mut().into_key_area_slice(), self.idx, key);
-            slice_insert(self.node.reborrow_mut().into_val_area_slice(), self.idx, val);
-            slice_insert(self.node.reborrow_mut().into_edge_area_slice(), self.idx + 1, edge.node);
+            *self.node.len_mut() += 1;
+            slice_insert(self.node.key_area_slice(), self.idx, key);
+            slice_insert(self.node.val_area_slice(), self.idx, val);
+            slice_insert(self.node.edge_area_slice(), self.idx + 1, edge.node);
 
             self.node.correct_childrens_parent_links((self.idx + 1)..=self.node.len());
         }
@@ -1134,12 +1141,13 @@ 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 into_key_mut(self) -> &'a mut K {
-        unsafe { self.node.into_key_area_mut_at(self.idx).assume_init_mut() }
+    pub fn key_mut(&mut self) -> &mut K {
+        unsafe { self.node.key_area_mut_at(self.idx).assume_init_mut() }
     }
 
     pub fn into_val_mut(self) -> &'a mut V {
-        unsafe { self.node.into_val_area_mut_at(self.idx).assume_init_mut() }
+        let leaf = self.node.into_leaf_mut();
+        unsafe { leaf.vals.get_unchecked_mut(self.idx).assume_init_mut() }
     }
 }
 
@@ -1154,7 +1162,7 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>
         // We cannot call separate key and value methods, because calling the second one
         // invalidates the reference returned by the first.
         unsafe {
-            let leaf = NodeRef::as_leaf_mut(&mut self.node.reborrow_mut());
+            let leaf = self.node.as_leaf_mut();
             let key = leaf.keys.get_unchecked_mut(self.idx).assume_init_mut();
             let val = leaf.vals.get_unchecked_mut(self.idx).assume_init_mut();
             (key, val)
@@ -1196,7 +1204,7 @@ impl<'a, K: 'a, V: 'a, NodeType> Handle<NodeRef<marker::Mut<'a>, K, V, NodeType>
                 new_len,
             );
 
-            *self.node.reborrow_mut().into_len_mut() = self.idx as u16;
+            *self.node.len_mut() = self.idx as u16;
             (k, v)
         }
     }
@@ -1227,9 +1235,9 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, mark
         mut self,
     ) -> ((K, V), Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>) {
         unsafe {
-            let k = slice_remove(self.node.reborrow_mut().into_key_area_slice(), self.idx);
-            let v = slice_remove(self.node.reborrow_mut().into_val_area_slice(), self.idx);
-            *self.node.reborrow_mut().into_len_mut() -= 1;
+            let k = slice_remove(self.node.key_area_slice(), self.idx);
+            let v = slice_remove(self.node.val_area_slice(), self.idx);
+            *self.node.len_mut() -= 1;
             ((k, v), self.left_edge())
         }
     }
@@ -1374,29 +1382,27 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
         });
 
         unsafe {
-            *left_node.reborrow_mut().into_len_mut() = new_left_len as u16;
+            *left_node.len_mut() = new_left_len as u16;
 
-            let parent_key =
-                slice_remove(parent_node.reborrow_mut().into_key_area_slice(), parent_idx);
-            left_node.reborrow_mut().into_key_area_mut_at(old_left_len).write(parent_key);
+            let parent_key = slice_remove(parent_node.key_area_slice(), parent_idx);
+            left_node.key_area_mut_at(old_left_len).write(parent_key);
             ptr::copy_nonoverlapping(
                 right_node.reborrow().key_area().as_ptr(),
-                left_node.reborrow_mut().into_key_area_slice().as_mut_ptr().add(old_left_len + 1),
+                left_node.key_area_slice().as_mut_ptr().add(old_left_len + 1),
                 right_len,
             );
 
-            let parent_val =
-                slice_remove(parent_node.reborrow_mut().into_val_area_slice(), parent_idx);
-            left_node.reborrow_mut().into_val_area_mut_at(old_left_len).write(parent_val);
+            let parent_val = slice_remove(parent_node.val_area_slice(), parent_idx);
+            left_node.val_area_mut_at(old_left_len).write(parent_val);
             ptr::copy_nonoverlapping(
                 right_node.reborrow().val_area().as_ptr(),
-                left_node.reborrow_mut().into_val_area_slice().as_mut_ptr().add(old_left_len + 1),
+                left_node.val_area_slice().as_mut_ptr().add(old_left_len + 1),
                 right_len,
             );
 
-            slice_remove(&mut parent_node.reborrow_mut().into_edge_area_slice(), parent_idx + 1);
+            slice_remove(&mut parent_node.edge_area_slice(), parent_idx + 1);
             parent_node.correct_childrens_parent_links(parent_idx + 1..old_parent_len);
-            *parent_node.reborrow_mut().into_len_mut() -= 1;
+            *parent_node.len_mut() -= 1;
 
             if parent_node.height > 1 {
                 // SAFETY: the height of the nodes being merged is one below the height
@@ -1405,11 +1411,7 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
                 let right_node = right_node.cast_to_internal_unchecked();
                 ptr::copy_nonoverlapping(
                     right_node.reborrow().edge_area().as_ptr(),
-                    left_node
-                        .reborrow_mut()
-                        .into_edge_area_slice()
-                        .as_mut_ptr()
-                        .add(old_left_len + 1),
+                    left_node.edge_area_slice().as_mut_ptr().add(old_left_len + 1),
                     right_len + 1,
                 );
 
@@ -1511,14 +1513,14 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
                 move_kv(left_kv, new_left_len, parent_kv, 0, 1);
             }
 
-            *left_node.reborrow_mut().into_len_mut() -= count as u16;
-            *right_node.reborrow_mut().into_len_mut() += count as u16;
+            *left_node.len_mut() -= count as u16;
+            *right_node.len_mut() += count as u16;
 
             match (left_node.reborrow_mut().force(), right_node.reborrow_mut().force()) {
                 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
                     // Make room for stolen edges.
                     let left = left.reborrow();
-                    let right_edges = right.reborrow_mut().into_edge_area_slice().as_mut_ptr();
+                    let right_edges = right.edge_area_slice().as_mut_ptr();
                     ptr::copy(right_edges, right_edges.add(count), old_right_len + 1);
                     right.correct_childrens_parent_links(count..count + old_right_len + 1);
 
@@ -1569,8 +1571,8 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
                 ptr::copy(right_kv.1.add(count), right_kv.1, new_right_len);
             }
 
-            *left_node.reborrow_mut().into_len_mut() += count as u16;
-            *right_node.reborrow_mut().into_len_mut() -= count as u16;
+            *left_node.len_mut() += count as u16;
+            *right_node.len_mut() -= count as u16;
 
             match (left_node.reborrow_mut().force(), right_node.reborrow_mut().force()) {
                 (ForceResult::Internal(left), ForceResult::Internal(mut right)) => {
@@ -1578,7 +1580,7 @@ impl<'a, K: 'a, V: 'a> BalancingContext<'a, K, V> {
                     move_edges(right.reborrow(), 0, left, old_left_len + 1, count);
 
                     // Fill gap where stolen edges used to be.
-                    let right_edges = right.reborrow_mut().into_edge_area_slice().as_mut_ptr();
+                    let right_edges = right.edge_area_slice().as_mut_ptr();
                     ptr::copy(right_edges.add(count), right_edges, new_right_len + 1);
                     right.correct_childrens_parent_links(0..=new_right_len);
                 }
@@ -1612,7 +1614,7 @@ unsafe fn move_edges<'a, K: 'a, V: 'a>(
 ) {
     unsafe {
         let source_ptr = source.edge_area().as_ptr();
-        let dest_ptr = dest.reborrow_mut().into_edge_area_slice().as_mut_ptr();
+        let dest_ptr = dest.edge_area_slice().as_mut_ptr();
         ptr::copy_nonoverlapping(source_ptr.add(source_offset), dest_ptr.add(dest_offset), count);
         dest.correct_childrens_parent_links(dest_offset..dest_offset + count);
     }
@@ -1708,8 +1710,8 @@ impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal>, ma
 
                 move_kv(left_kv, new_left_len, right_kv, 0, new_right_len);
 
-                *left_node.reborrow_mut().into_len_mut() = new_left_len as u16;
-                *right_node.reborrow_mut().into_len_mut() = new_right_len as u16;
+                *left_node.len_mut() = new_left_len as u16;
+                *right_node.len_mut() = new_right_len as u16;
 
                 match (left_node.force(), right_node.force()) {
                     (ForceResult::Internal(left), ForceResult::Internal(right)) => {