Update Tokio to Rust 2018 (#1082)

tokio-fs/tests/dir.rs

@@ -1,6 +1,4 @@
-extern crate futures;
-extern crate tempdir;
-extern crate tokio_fs;
+#![deny(warnings, rust_2018_idioms)]
 
 use futures::{Future, Stream};
 use std::fs;

tokio-fs/tests/file.rs

@@ -1,19 +1,13 @@
-extern crate futures;
-extern crate rand;
-extern crate tempfile;
-extern crate tokio_fs;
-extern crate tokio_io;
-
-use tokio_fs::*;
-use tokio_io::io;
+#![deny(warnings, rust_2018_idioms)]
 
 use futures::future::poll_fn;
 use futures::Future;
 use rand::{distributions, thread_rng, Rng};
-use tempfile::Builder as TmpBuilder;
-
 use std::fs;
 use std::io::SeekFrom;
+use tempfile::Builder as TmpBuilder;
+use tokio_fs::*;
+use tokio_io::io;
 
 mod pool;
 

tokio-fs/tests/link.rs

@@ -1,8 +1,5 @@
-extern crate futures;
-extern crate tempdir;
-extern crate tokio_fs;
+#![deny(warnings, rust_2018_idioms)]
 
-use futures::Future;
 use std::fs;
 use std::io::prelude::*;
 use std::io::BufReader;
@@ -38,6 +35,8 @@ fn test_hard_link() {
 #[cfg(unix)]
 #[test]
 fn test_symlink() {
+    use futures::Future;
+
     let dir = TempDir::new("base").unwrap();
     let src = dir.path().join("src.txt");
     let dst = dir.path().join("dst.txt");

tokio-fs/tests/pool/mod.rs

@@ -1,5 +1,5 @@
-extern crate futures;
-extern crate tokio_threadpool;
+use futures;
+use tokio_threadpool;
 
 use self::tokio_threadpool::Builder;
 use futures::sync::oneshot;