Set Sink types as must_use

src/channel.rs

@@ -23,6 +23,7 @@ use reactor::{Handle, PollEvented};
 /// This type is created by the [`channel`] function.
 ///
 /// [`channel`]: fn.channel.html
+#[must_use = "sinks do nothing unless polled"]
 pub struct Sender<T> {
     tx: channel::Sender<T>,
 }

src/net/udp/frame.rs

@@ -55,6 +55,7 @@ pub trait UdpCodec {
 ///
 /// You can acquire a `UdpFramed` instance by using the `UdpSocket::framed`
 /// adapter.
+#[must_use = "sinks do nothing unless polled"]
 pub struct UdpFramed<C> {
     socket: UdpSocket,
     codec: C,