Update Tokio to Rust 2018 (#1082)

tokio-sync/src/lock.rs

@@ -8,11 +8,9 @@
 //! This allows you to do something along the lines of:
 //!
 //! ```rust,no_run
-//! # #[macro_use]
-//! # extern crate futures;
-//! # extern crate tokio;
-//! # use futures::{future, Poll, Async, Future, Stream};
+//! use futures::{try_ready, future, Poll, Async, Future, Stream};
 //! use tokio::sync::lock::{Lock, LockGuard};
+//!
 //! struct MyType<S> {
 //!     lock: Lock<S>,
 //! }
@@ -37,14 +35,13 @@
 //!         }
 //!     }
 //! }
-//! # fn main() {}
 //! ```
 //!
-//!   [`Lock`]: struct.Lock.html
-//!   [`LockGuard`]: struct.LockGuard.html
+//! [`Lock`]: struct.Lock.html
+//! [`LockGuard`]: struct.LockGuard.html
 
+use crate::semaphore;
 use futures::Async;
-use semaphore;
 use std::cell::UnsafeCell;
 use std::fmt;
 use std::ops::{Deref, DerefMut};
@@ -176,7 +173,7 @@ impl<T> DerefMut for LockGuard<T> {
 }
 
 impl<T: fmt::Display> fmt::Display for LockGuard<T> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(&**self, f)
     }
 }