add #[must_use] to more futures and streams (#1309)

tokio-fs/src/create_dir.rs

@@ -17,6 +17,7 @@ pub fn create_dir<P: AsRef<Path>>(path: P) -> CreateDirFuture<P> {
 
 /// Future returned by `create_dir`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct CreateDirFuture<P>
 where
     P: AsRef<Path>,

tokio-fs/src/create_dir_all.rs

@@ -18,6 +18,7 @@ pub fn create_dir_all<P: AsRef<Path>>(path: P) -> CreateDirAllFuture<P> {
 
 /// Future returned by `create_dir_all`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct CreateDirAllFuture<P>
 where
     P: AsRef<Path>,

tokio-fs/src/file/clone.rs

@@ -13,6 +13,7 @@ use std::task::Poll;
 ///
 /// Will panic if polled after returning an item or error.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct CloneFuture {
     file: Option<File>,
 }

tokio-fs/src/file/create.rs

@@ -8,6 +8,7 @@ use std::task::Context;
 use std::task::Poll;
 
 /// Future returned by `File::create` and resolves to a `File` instance.
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 #[derive(Debug)]
 pub struct CreateFuture<P> {
     path: P,

tokio-fs/src/file/metadata.rs

@@ -11,6 +11,7 @@ const POLL_AFTER_RESOLVE: &str = "Cannot poll MetadataFuture after it resolves";
 
 /// Future returned by `File::metadata` and resolves to a `(File, Metadata)` instance.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct MetadataFuture {
     file: Option<File>,
 }

tokio-fs/src/file/open.rs

@@ -9,6 +9,7 @@ use std::task::Poll;
 
 /// Future returned by `File::open` and resolves to a `File` instance.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct OpenFuture<P: Unpin> {
     options: StdOpenOptions,
     path: P,

tokio-fs/src/file/seek.rs

@@ -7,6 +7,7 @@ use std::task::Poll;
 
 /// Future returned by `File::seek`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct SeekFuture {
     inner: Option<File>,
     pos: io::SeekFrom,

tokio-fs/src/hard_link.rs

@@ -20,6 +20,7 @@ pub fn hard_link<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> HardLinkFutu
 
 /// Future returned by `hard_link`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct HardLinkFuture<P, Q>
 where
     P: AsRef<Path>,

tokio-fs/src/metadata.rs

@@ -17,6 +17,7 @@ where
 
 /// Future returned by `metadata`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct MetadataFuture<P>
 where
     P: AsRef<Path> + Send + 'static,

tokio-fs/src/read.rs

@@ -38,6 +38,7 @@ where
 
 /// A future used to open a file and read its entire contents into a buffer.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct ReadFile<P: AsRef<Path> + Send + Unpin + 'static> {
     state: State<P>,
 }

tokio-fs/src/read_dir.rs

@@ -24,6 +24,7 @@ where
 
 /// Future returned by `read_dir`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct ReadDirFuture<P>
 where
     P: AsRef<Path> + Send + 'static,
@@ -68,6 +69,7 @@ where
 /// [`Stream`]: ../futures/stream/trait.Stream.html
 /// [`Err`]: https://doc.rust-lang.org/std/result/enum.Result.html#variant.Err
 #[derive(Debug)]
+#[must_use = "streams do nothing unless polled"]
 pub struct ReadDir(StdReadDir);
 
 impl Stream for ReadDir {

tokio-fs/src/read_link.rs

@@ -17,6 +17,7 @@ pub fn read_link<P: AsRef<Path>>(path: P) -> ReadLinkFuture<P> {
 
 /// Future returned by `read_link`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct ReadLinkFuture<P>
 where
     P: AsRef<Path>,

tokio-fs/src/remove_dir.rs

@@ -17,6 +17,7 @@ pub fn remove_dir<P: AsRef<Path>>(path: P) -> RemoveDirFuture<P> {
 
 /// Future returned by `remove_dir`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct RemoveDirFuture<P>
 where
     P: AsRef<Path>,

tokio-fs/src/remove_file.rs

@@ -21,6 +21,7 @@ pub fn remove_file<P: AsRef<Path>>(path: P) -> RemoveFileFuture<P> {
 
 /// Future returned by `remove_file`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct RemoveFileFuture<P>
 where
     P: AsRef<Path>,

tokio-fs/src/rename.rs

@@ -20,6 +20,7 @@ pub fn rename<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> RenameFuture<P,
 
 /// Future returned by `rename`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct RenameFuture<P, Q>
 where
     P: AsRef<Path>,

tokio-fs/src/set_permissions.rs

@@ -17,6 +17,7 @@ pub fn set_permissions<P: AsRef<Path>>(path: P, perm: fs::Permissions) -> SetPer
 
 /// Future returned by `set_permissions`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct SetPermissionsFuture<P>
 where
     P: AsRef<Path>,

tokio-fs/src/symlink_metadata.rs

@@ -21,6 +21,7 @@ where
 
 /// Future returned by `symlink_metadata`.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct SymlinkMetadataFuture<P>
 where
     P: AsRef<Path> + Send + 'static,

tokio-fs/src/write.rs

@@ -41,6 +41,7 @@ where
 /// A future used to open a file for writing and write the entire contents
 /// of some data to it.
 #[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct WriteFile<P: AsRef<Path> + Send + Unpin + 'static, C: AsRef<[u8]> + Unpin> {
     state: State<P, C>,
 }