4 files changed, 13 insertions, 3 deletions
diff --git a/src/libcore/clone.rs b/src/libcore/clone.rs
index 9a412e57294..eb101fc72fd 100644
--- a/src/libcore/clone.rs
+++ b/src/libcore/clone.rs
@@ -219,7 +219,7 @@ mod impls {
         }
     }
 
-    // Shared references can be cloned, but mutable references *cannot*!
+    /// Shared references can be cloned, but mutable references *cannot*!
     #[stable(feature = "rust1", since = "1.0.0")]
     impl<T: ?Sized> Clone for &T {
         #[inline]
@@ -227,4 +227,9 @@ mod impls {
             *self
         }
     }
+
+    /// Shared references can be cloned, but mutable references *cannot*!
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg(not(bootstrap))]
+    impl<T: ?Sized> !Clone for &mut T {}
 }
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 94fc2fd357a..0bee16f98bd 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -98,6 +98,7 @@
 #![feature(is_sorted)]
 #![feature(lang_items)]
 #![feature(link_llvm_intrinsics)]
+#![cfg_attr(not(bootstrap), feature(negative_impls))]
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(exhaustive_patterns)]
diff --git a/src/libcore/marker.rs b/src/libcore/marker.rs
index 2b908f07af8..549f80de36a 100644
--- a/src/libcore/marker.rs
+++ b/src/libcore/marker.rs
@@ -87,7 +87,7 @@ impl<T: ?Sized> !Send for *mut T {}
     message = "the size for values of type `{Self}` cannot be known at compilation time",
     label = "doesn't have a size known at compile-time",
     note = "to learn more, visit <https://doc.rust-lang.org/book/\
-          ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>"
+            ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>"
 )]
 #[fundamental] // for Default, for example, which requires that `[T]: !Default` be evaluatable
 #[cfg_attr(not(bootstrap), rustc_specialization_trait)]
@@ -790,7 +790,7 @@ mod copy_impls {
     #[stable(feature = "rust1", since = "1.0.0")]
     impl<T: ?Sized> Copy for *mut T {}
 
-    // Shared references can be copied, but mutable references *cannot*!
+    /// Shared references can be copied, but mutable references *cannot*!
     #[stable(feature = "rust1", since = "1.0.0")]
     impl<T: ?Sized> Copy for &T {}
 }
diff --git a/src/libcore/ops/deref.rs b/src/libcore/ops/deref.rs
index 68244fdb381..e2deeb55661 100644
--- a/src/libcore/ops/deref.rs
+++ b/src/libcore/ops/deref.rs
@@ -81,6 +81,10 @@ impl<T: ?Sized> Deref for &T {
     }
 }
 
+#[cfg(not(bootstrap))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> !DerefMut for &T {}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized> Deref for &mut T {
     type Target = T;