Fix unused_results complaining rustc lint in codegen for adjacently tagged enum

serde/src/private/mod.rs

@@ -13,6 +13,7 @@ pub use lib::convert::{From, Into};
 pub use lib::default::Default;
 pub use lib::fmt::{self, Formatter};
 pub use lib::marker::PhantomData;
+pub use lib::mem;
 pub use lib::option::Option::{self, None, Some};
 pub use lib::ptr;
 pub use lib::result::Result::{self, Err, Ok};