Set Future types as must_use

src/io/copy.rs

@@ -8,6 +8,7 @@ use futures::{Future, Poll};
 /// bytes copied or an error if one happens.
 ///
 /// [`copy`]: fn.copy.html
+#[must_use = "futures do nothing unless polled"]
 pub struct Copy<R, W> {
     reader: R,
     read_done: bool,

src/io/flush.rs

@@ -9,6 +9,7 @@ use futures::{Poll, Future, Async};
 /// Created by the [`flush`] function.
 ///
 /// [`flush`]: fn.flush.html
+#[must_use = "futures do nothing unless polled"]
 pub struct Flush<A> {
     a: Option<A>,
 }

src/io/read.rs

@@ -26,6 +26,7 @@ pub fn read<R, T>(rd: R, buf: T) -> Read<R, T>
 /// a buffer.
 ///
 /// Created by the [`read`] function.
+#[must_use = "futures do nothing unless polled"]
 pub struct Read<R, T> {
     state: State<R, T>,
 }

src/io/read_exact.rs

@@ -9,6 +9,7 @@ use futures::{Poll, Future};
 /// Created by the [`read_exact`] function.
 ///
 /// [`read_exact`]: fn.read_exact.html
+#[must_use = "futures do nothing unless polled"]
 pub struct ReadExact<A, T> {
     state: State<A, T>,
 }

src/io/read_to_end.rs

@@ -9,6 +9,7 @@ use futures::{Poll, Future};
 /// Created by the [`read_to_end`] function.
 ///
 /// [`read_to_end`]: fn.read_to_end.html
+#[must_use = "futures do nothing unless polled"]
 pub struct ReadToEnd<A> {
     state: State<A>,
 }

src/io/read_until.rs

@@ -9,6 +9,7 @@ use futures::{Poll, Future};
 /// Created by the [`read_until`] function.
 ///
 /// [`read_until`]: fn.read_until.html
+#[must_use = "futures do nothing unless polled"]
 pub struct ReadUntil<A> {
     state: State<A>,
 }

src/io/write_all.rs

@@ -8,6 +8,7 @@ use futures::{Poll, Future};
 /// This is created by the [`write_all`] top-level method.
 ///
 /// [`write_all`]: fn.write_all.html
+#[must_use = "futures do nothing unless polled"]
 pub struct WriteAll<A, T> {
     state: State<A, T>,
 }

src/net/tcp.rs

@@ -235,10 +235,12 @@ pub struct TcpStream {
 
 /// Future returned by `TcpStream::connect` which will resolve to a `TcpStream`
 /// when the stream is connected.
+#[must_use = "futures do nothing unless polled"]
 pub struct TcpStreamNew {
     inner: TcpStreamNewState,
 }
 
+#[must_use = "futures do nothing unless polled"]
 enum TcpStreamNewState {
     Waiting(TcpStream),
     Error(io::Error),

src/net/udp/mod.rs

@@ -394,6 +394,7 @@ impl fmt::Debug for UdpSocket {
 /// A future used to write the entire contents of some data to a UDP socket.
 ///
 /// This is created by the `UdpSocket::send_dgram` method.
+#[must_use = "futures do nothing unless polled"]
 pub struct SendDgram<T> {
     state: SendState<T>,
 }
@@ -441,6 +442,7 @@ impl<T> Future for SendDgram<T>
 /// A future used to receive a datagram from a UDP socket.
 ///
 /// This is created by the `UdpSocket::recv_dgram` method.
+#[must_use = "futures do nothing unless polled"]
 pub struct RecvDgram<T> {
     state: RecvState<T>,
 }

src/reactor/timeout.rs

@@ -18,6 +18,7 @@ use reactor::timeout_token::TimeoutToken;
 /// Note that timeouts are not intended for high resolution timers, but rather
 /// they will likely fire some granularity after the exact instant that they're
 /// otherwise indicated to fire at.
+#[must_use = "futures do nothing unless polled"]
 #[derive(Debug)]
 pub struct Timeout {
     token: TimeoutToken,