From 607315b2c34bb6c373cf3fc8283ab6b05414d114 Mon Sep 17 00:00:00 2001
From: Stein Somers <git@steinsomers.be>
Date: Thu, 9 Apr 2020 20:16:30 +0200
Subject: [PATCH 1/2] Kill comment left behind by a last minute change in
 #70795

---
 src/liballoc/collections/btree/map.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/liballoc/collections/btree/map.rs b/src/liballoc/collections/btree/map.rs
index a1e59b2e6af..3b42055d4a8 100644
--- a/src/liballoc/collections/btree/map.rs
+++ b/src/liballoc/collections/btree/map.rs
@@ -2788,8 +2788,6 @@ impl<'a, K: 'a, V: 'a> Handle<NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInter
                             pos.next_unchecked();
                         }
                     }
-
-                    // This internal node might be underfull, but only if it's the root.
                     break;
                 }
             }

From de39a4f6218fac9d0b9d09a928613b4aa2407a31 Mon Sep 17 00:00:00 2001
From: Stein Somers <git@steinsomers.be>
Date: Thu, 9 Apr 2020 20:19:18 +0200
Subject: [PATCH 2/2] Respect the comment: no root unless the borrow type is
 `Mut`

---
 src/liballoc/collections/btree/node.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/liballoc/collections/btree/node.rs b/src/liballoc/collections/btree/node.rs
index bc4e2711670..84d34db2d45 100644
--- a/src/liballoc/collections/btree/node.rs
+++ b/src/liballoc/collections/btree/node.rs
@@ -161,7 +161,7 @@ impl<K, V> Root<K, V> {
         NodeRef {
             height: self.height,
             node: self.node.as_ptr(),
-            root: self as *const _ as *mut _,
+            root: ptr::null(),
             _marker: PhantomData,
         }
     }
@@ -179,7 +179,7 @@ impl<K, V> Root<K, V> {
         NodeRef {
             height: self.height,
             node: self.node.as_ptr(),
-            root: ptr::null_mut(), // FIXME: Is there anything better to do here?
+            root: ptr::null(),
             _marker: PhantomData,
         }
     }