Use DerefMut

Author: JohnTitor

src/libcore/option.rs

@@ -136,7 +136,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use crate::iter::{FromIterator, FusedIterator, TrustedLen};
-use crate::{convert, fmt, hint, mem, ops::{self, Deref}};
+use crate::{convert, fmt, hint, mem, ops::{self, Deref, DerefMut}};
 use crate::pin::Pin;
 
 // Note that this is not a lang item per se, but it has a hidden dependency on

src/libcore/result.rs

@@ -232,7 +232,7 @@
 
 use crate::fmt;
 use crate::iter::{FromIterator, FusedIterator, TrustedLen};
-use crate::ops::{self, Deref};
+use crate::ops::{self, Deref, DerefMut};
 
 /// `Result` is a type that represents either success ([`Ok`]) or failure ([`Err`]).
 ///