refactor(lib): convert usage of tokio_core::io to tokio_io

This commit updates to the most recent versions (released today) of the various
Tokio libraries in use. Namely the `tokio_core::io` module has now been
deprecated in favor of an external `tokio-io` crate. This commit pulls in that
crate and uses the `AsyncRead + AsyncWrite` abstraction instead of `Io` from
tokio-core.

BREAKING CHANGE: Any external types that were using that had implemented `Io` will need to 
  implement `AsyncRead + AsyncWrite` from tokio_io.

Cargo.toml

@@ -22,17 +22,17 @@ include = [
 [dependencies]
 base64 = "0.4"
 bytes = "0.4"
-futures = "0.1.7"
+futures = "0.1.11"
 futures-cpupool = "0.1"
 httparse = "1.0"
 language-tags = "0.2"
 log = "0.3"
 mime = "0.2"
-relay = "0.1"
 time = "0.1"
-tokio-core = "0.1"
+tokio-core = "0.1.6"
 tokio-proto = "0.1"
 tokio-service = "0.1"
+tokio-io = "0.1"
 unicase = "1.0"
 url = "1.0"
 

src/client/connect.rs

@@ -3,7 +3,7 @@ use std::io;
 //use std::net::SocketAddr;
 
 use futures::{Future, Poll, Async};
-use tokio::io::Io;
+use tokio_io::{AsyncRead, AsyncWrite};
 use tokio::reactor::Handle;
 use tokio::net::{TcpStream, TcpStreamNew};
 use tokio_service::Service;
@@ -18,7 +18,7 @@ use super::dns;
 /// `Request=Url` and `Response: Io` instead.
 pub trait Connect: Service<Request=Url, Error=io::Error> + 'static {
     /// The connected Io Stream.
-    type Output: Io + 'static;
+    type Output: AsyncRead + AsyncWrite + 'static;
     /// A Future that will resolve to the connected Stream.
     type Future: Future<Item=Self::Output, Error=io::Error> + 'static;
     /// Connect to a remote address.
@@ -27,7 +27,7 @@ pub trait Connect: Service<Request=Url, Error=io::Error> + 'static {
 
 impl<T> Connect for T
 where T: Service<Request=Url, Error=io::Error> + 'static,
-      T::Response: Io,
+      T::Response: AsyncRead + AsyncWrite,
       T::Future: Future<Error=io::Error>,
 {
     type Output = T::Response;

src/client/mod.rs

@@ -11,8 +11,8 @@ use std::rc::Rc;
 use std::time::Duration;
 
 use futures::{Poll, Async, Future, Stream};
-use relay;
+use futures::unsync::oneshot;
-use tokio::io::Io;
+use tokio_io::{AsyncRead, AsyncWrite};
 use tokio::reactor::Handle;
 use tokio_proto::BindClient;
 use tokio_proto::streaming::Message;
@@ -149,12 +149,12 @@ where C: Connect,
             let pool_key = Rc::new(url[..::url::Position::BeforePath].to_owned());
             self.connector.connect(url)
                 .map(move |io| {
-                    let (tx, rx) = relay::channel();
+                    let (tx, rx) = oneshot::channel();
                     let client = HttpClient {
                         client_rx: RefCell::new(Some(rx)),
                     }.bind_client(&handle, io);
                     let pooled = pool.pooled(pool_key, client);
-                    tx.complete(pooled.clone());
+                    drop(tx.send(pooled.clone()));
                     pooled
                 })
         };
@@ -207,11 +207,11 @@ impl<C, B> fmt::Debug for Client<C, B> {
 type TokioClient<B> = ClientProxy<Message<http::RequestHead, B>, Message<http::ResponseHead, TokioBody>, ::Error>;
 
 struct HttpClient<B> {
-    client_rx: RefCell<Option<relay::Receiver<Pooled<TokioClient<B>>>>>,
+    client_rx: RefCell<Option<oneshot::Receiver<Pooled<TokioClient<B>>>>>,
 }
 
 impl<T, B> ClientProto<T> for HttpClient<B>
-where T: Io + 'static,
+where T: AsyncRead + AsyncWrite + 'static,
       B: Stream<Error=::Error> + 'static,
       B::Item: AsRef<[u8]>,
 {
@@ -232,12 +232,12 @@ where T: Io + 'static,
 }
 
 struct BindingClient<T, B> {
-    rx: relay::Receiver<Pooled<TokioClient<B>>>,
+    rx: oneshot::Receiver<Pooled<TokioClient<B>>>,
     io: Option<T>,
 }
 
 impl<T, B> Future for BindingClient<T, B>
-where T: Io + 'static,
+where T: AsyncRead + AsyncWrite + 'static,
       B: Stream<Error=::Error>,
       B::Item: AsRef<[u8]>,
 {

src/client/pool.rs

@@ -7,7 +7,7 @@ use std::rc::Rc;
 use std::time::{Duration, Instant};
 
 use futures::{Future, Async, Poll};
-use relay;
+use futures::unsync::oneshot;
 
 use http::{KeepAlive, KA};
 
@@ -18,7 +18,7 @@ pub struct Pool<T> {
 struct PoolInner<T> {
     enabled: bool,
     idle: HashMap<Rc<String>, Vec<Entry<T>>>,
-    parked: HashMap<Rc<String>, VecDeque<relay::Sender<Entry<T>>>>,
+    parked: HashMap<Rc<String>, VecDeque<oneshot::Sender<Entry<T>>>>,
     timeout: Option<Duration>,
 }
 
@@ -44,32 +44,34 @@ impl<T: Clone> Pool<T> {
 
     fn put(&mut self, key: Rc<String>, entry: Entry<T>) {
         trace!("Pool::put {:?}", key);
+        let mut inner = self.inner.borrow_mut();
+        //let inner = &mut *inner;
         let mut remove_parked = false;
-        let tx = self.inner.borrow_mut().parked.get_mut(&key).and_then(|parked| {
+        let mut entry = Some(entry);
-            let mut ret = None;
+        if let Some(parked) = inner.parked.get_mut(&key) {
             while let Some(tx) = parked.pop_front() {
-                if !tx.is_canceled() {
+                match tx.send(entry.take().unwrap()) {
-                    ret = Some(tx);
+                    Ok(()) => break,
-                    break;
+                    Err(e) => {
-                }
                         trace!("Pool::put removing canceled parked {:?}", key);
+                        entry = Some(e);
+                    }
+                }
             }
             remove_parked = parked.is_empty();
-            ret
+        }
-        });
         if remove_parked {
-            self.inner.borrow_mut().parked.remove(&key);
+            inner.parked.remove(&key);
         }
 
-        if let Some(tx) = tx {
+        match entry {
-            trace!("Pool::put found parked {:?}", key);
+            Some(entry) => {
-            tx.complete(entry);
+                inner.idle.entry(key)
-        } else {
-            self.inner.borrow_mut()
-                .idle.entry(key)
                      .or_insert(Vec::new())
                      .push(entry);
             }
+            None => trace!("Pool::put found parked {:?}", key),
+        }
     }
 
     pub fn pooled(&self, key: Rc<String>, value: T) -> Pooled<T> {
@@ -100,7 +102,7 @@ impl<T: Clone> Pool<T> {
         }
     }
 
-    fn park(&mut self, key: Rc<String>, tx: relay::Sender<Entry<T>>) {
+    fn park(&mut self, key: Rc<String>, tx: oneshot::Sender<Entry<T>>) {
         trace!("Pool::park {:?}", key);
         self.inner.borrow_mut()
             .parked.entry(key)
@@ -191,7 +193,7 @@ struct Entry<T> {
 pub struct Checkout<T> {
     key: Rc<String>,
     pool: Pool<T>,
-    parked: Option<relay::Receiver<Entry<T>>>,
+    parked: Option<oneshot::Receiver<Entry<T>>>,
 }
 
 impl<T: Clone> Future for Checkout<T> {
@@ -247,7 +249,7 @@ impl<T: Clone> Future for Checkout<T> {
             Some(entry) => Ok(Async::Ready(self.pool.reuse(self.key.clone(), entry))),
             None => {
                 if self.parked.is_none() {
-                    let (tx, mut rx) = relay::channel();
+                    let (tx, mut rx) = oneshot::channel();
                     let _ = rx.poll(); // park this task
                     self.pool.park(self.key.clone(), tx);
                     self.parked = Some(rx);
@@ -279,6 +281,7 @@ mod tests {
     use std::rc::Rc;
     use std::time::Duration;
     use futures::{Async, Future};
+    use futures::future;
     use http::KeepAlive;
     use super::Pool;
 
@@ -297,7 +300,7 @@ mod tests {
 
     #[test]
     fn test_pool_checkout_returns_none_if_expired() {
-        ::futures::lazy(|| {
+        future::lazy(|| {
             let pool = Pool::new(true, Some(Duration::from_secs(1)));
             let key = Rc::new("foo".to_string());
             let mut pooled = pool.pooled(key.clone(), 41);
@@ -339,7 +342,7 @@ mod tests {
         let pooled1 = pool.pooled(key.clone(), 41);
 
         let mut pooled = pooled1.clone();
-        let checkout = pool.checkout(&key).join(::futures::lazy(move || {
+        let checkout = pool.checkout(&key).join(future::lazy(move || {
             // the checkout future will park first,
             // and then this lazy future will be polled, which will insert
             // the pooled back into the pool

src/http/conn.rs

@@ -5,7 +5,7 @@ use std::time::Instant;
 
 use futures::{Poll, Async, AsyncSink, Stream, Sink, StartSend};
 use futures::task::Task;
-use tokio::io::Io;
+use tokio_io::{AsyncRead, AsyncWrite};
 use tokio_proto::streaming::pipeline::{Frame, Transport};
 
 use header::{ContentLength, TransferEncoding};
@@ -16,7 +16,7 @@ use version::HttpVersion;
 
 
 /// This handles a connection, which will have been established over an
-/// `Io` (like a socket), and will likely include multiple
+/// `AsyncRead + AsyncWrite` (like a socket), and will likely include multiple
 /// `Transaction`s over HTTP.
 ///
 /// The connection will determine when a message begins and ends as well as
@@ -29,7 +29,7 @@ pub struct Conn<I, B, T, K = KA> {
 }
 
 impl<I, B, T, K> Conn<I, B, T, K>
-where I: Io,
+where I: AsyncRead + AsyncWrite,
       B: AsRef<[u8]>,
       T: Http1Transaction,
       K: KeepAlive
@@ -155,7 +155,7 @@ where I: Io,
     }
 
     fn maybe_park_read(&mut self) {
-        if self.io.poll_read().is_ready() {
+        if !self.io.is_read_blocked() {
             // the Io object is ready to read, which means it will never alert
             // us that it is ready until we drain it. However, we're currently
             // finished reading, so we need to park the task to be able to
@@ -350,7 +350,7 @@ where I: Io,
 }
 
 impl<I, B, T, K> Stream for Conn<I, B, T, K>
-where I: Io,
+where I: AsyncRead + AsyncWrite,
       B: AsRef<[u8]>,
       T: Http1Transaction,
       K: KeepAlive,
@@ -385,7 +385,7 @@ where I: Io,
 }
 
 impl<I, B, T, K> Sink for Conn<I, B, T, K>
-where I: Io,
+where I: AsyncRead + AsyncWrite,
       B: AsRef<[u8]>,
       T: Http1Transaction,
       K: KeepAlive,
@@ -450,10 +450,15 @@ where I: Io,
         trace!("Conn::flush = {:?}", ret);
         ret
     }
+
+    fn close(&mut self) -> Poll<(), Self::SinkError> {
+        try_ready!(self.poll_complete());
+        self.io.io_mut().shutdown()
+    }
 }
 
 impl<I, B, T, K> Transport for Conn<I, B, T, K>
-where I: Io + 'static,
+where I: AsyncRead + AsyncWrite + 'static,
       B: AsRef<[u8]> + 'static,
       T: Http1Transaction + 'static,
       K: KeepAlive + 'static,
@@ -665,6 +670,7 @@ impl<'a, T: fmt::Debug + 'a, B: AsRef<[u8]> + 'a> fmt::Debug for DebugFrame<'a,
 #[cfg(test)]
 mod tests {
     use futures::{Async, Future, Stream, Sink};
+    use futures::future;
     use tokio_proto::streaming::pipeline::Frame;
 
     use http::{self, MessageHead, ServerTransaction};
@@ -705,7 +711,7 @@ mod tests {
 
     #[test]
     fn test_conn_parse_partial() {
-        let _: Result<(), ()> = ::futures::lazy(|| {
+        let _: Result<(), ()> = future::lazy(|| {
             let good_message = b"GET / HTTP/1.1\r\nHost: foo.bar\r\n\r\n".to_vec();
             let io = AsyncIo::new_buf(good_message, 10);
             let mut conn = Conn::<_, http::Chunk, ServerTransaction>::new(io, Default::default());
@@ -772,7 +778,7 @@ mod tests {
 
     #[test]
     fn test_conn_body_write_length() {
-        let _: Result<(), ()> = ::futures::lazy(|| {
+        let _: Result<(), ()> = future::lazy(|| {
             let io = AsyncIo::new_buf(vec![], 0);
             let mut conn = Conn::<_, http::Chunk, ServerTransaction>::new(io, Default::default());
             let max = ::http::io::MAX_BUFFER_SIZE + 4096;
@@ -800,7 +806,7 @@ mod tests {
 
     #[test]
     fn test_conn_body_write_chunked() {
-        let _: Result<(), ()> = ::futures::lazy(|| {
+        let _: Result<(), ()> = future::lazy(|| {
             let io = AsyncIo::new_buf(vec![], 4096);
             let mut conn = Conn::<_, http::Chunk, ServerTransaction>::new(io, Default::default());
             conn.state.writing = Writing::Body(Encoder::chunked(), None);
@@ -813,7 +819,7 @@ mod tests {
 
     #[test]
     fn test_conn_body_flush() {
-        let _: Result<(), ()> = ::futures::lazy(|| {
+        let _: Result<(), ()> = future::lazy(|| {
             let io = AsyncIo::new_buf(vec![], 1024 * 1024 * 5);
             let mut conn = Conn::<_, http::Chunk, ServerTransaction>::new(io, Default::default());
             conn.state.writing = Writing::Body(Encoder::length(1024 * 1024), None);
@@ -829,7 +835,7 @@ mod tests {
     #[test]
     fn test_conn_parking() {
         use std::sync::Arc;
-        use futures::task::Unpark;
+        use futures::executor::Unpark;
 
         struct Car {
             permit: bool,
@@ -847,7 +853,7 @@ mod tests {
         }
 
         // test that once writing is done, unparks
-        let f = ::futures::lazy(|| {
+        let f = future::lazy(|| {
             let io = AsyncIo::new_buf(vec![], 4096);
             let mut conn = Conn::<_, http::Chunk, ServerTransaction>::new(io, Default::default());
             conn.state.reading = Reading::KeepAlive;
@@ -861,7 +867,7 @@ mod tests {
 
 
         // test that flushing when not waiting on read doesn't unpark
-        let f = ::futures::lazy(|| {
+        let f = future::lazy(|| {
             let io = AsyncIo::new_buf(vec![], 4096);
             let mut conn = Conn::<_, http::Chunk, ServerTransaction>::new(io, Default::default());
             conn.state.writing = Writing::KeepAlive;
@@ -872,7 +878,7 @@ mod tests {
 
 
         // test that flushing and writing isn't done doesn't unpark
-        let f = ::futures::lazy(|| {
+        let f = future::lazy(|| {
             let io = AsyncIo::new_buf(vec![], 4096);
             let mut conn = Conn::<_, http::Chunk, ServerTransaction>::new(io, Default::default());
             conn.state.reading = Reading::KeepAlive;

src/http/h1/decode.rs

@@ -295,7 +295,7 @@ mod tests {
                 let (a, b) = self.split_at(n);
                 let mut buf = BytesMut::from(a);
                 *self = b;
-                Ok(buf.drain_to(n).freeze())
+                Ok(buf.split_to(n).freeze())
             } else {
                 Ok(Bytes::new())
             }

src/http/h1/parse.rs

@@ -55,7 +55,7 @@ impl Http1Transaction for ServerTransaction {
         };
 
         let mut headers = Headers::with_capacity(headers_len);
-        let slice = buf.drain_to(len).freeze();
+        let slice = buf.split_to(len).freeze();
         let path = slice.slice(path.0, path.1);
         // path was found to be utf8 by httparse
         let path = unsafe { ByteStr::from_utf8_unchecked(path) };
@@ -171,7 +171,7 @@ impl Http1Transaction for ClientTransaction {
         };
 
         let mut headers = Headers::with_capacity(headers_len);
-        let slice = buf.drain_to(len).freeze();
+        let slice = buf.split_to(len).freeze();
         headers.extend(HeadersAsBytesIter {
             headers: headers_indices[..headers_len].iter(),
             slice: slice,

src/http/io.rs

@@ -3,8 +3,7 @@ use std::fmt;
 use std::io::{self, Write};
 use std::ptr;
 
-use futures::Async;
+use tokio_io::{AsyncRead, AsyncWrite};
-use tokio::io::Io;
 
 use http::{Http1Transaction, h1, MessageHead, ParseResult, DebugTruncate};
 use bytes::{BytesMut, Bytes};
@@ -14,6 +13,7 @@ pub const MAX_BUFFER_SIZE: usize = 8192 + 4096 * 100;
 
 pub struct Buffered<T> {
     io: T,
+    read_blocked: bool,
     read_buf: BytesMut,
     write_buf: WriteBuf,
 }
@@ -27,12 +27,13 @@ impl<T> fmt::Debug for Buffered<T> {
     }
 }
 
-impl<T: Io> Buffered<T> {
+impl<T: AsyncRead + AsyncWrite> Buffered<T> {
     pub fn new(io: T) -> Buffered<T> {
         Buffered {
             io: io,
             read_buf: BytesMut::with_capacity(0),
             write_buf: WriteBuf::new(),
+            read_blocked: false,
         }
     }
 
@@ -49,14 +50,10 @@ impl<T: Io> Buffered<T> {
                     _ => break,
                 }
             }
-            self.read_buf.drain_to(i);
+            self.read_buf.split_to(i);
         }
     }
 
-    pub fn poll_read(&mut self) -> Async<()> {
-        self.io.poll_read()
-    }
-
     pub fn parse<S: Http1Transaction>(&mut self) -> ::Result<Option<MessageHead<S::Incoming>>> {
         self.reserve_read_buf();
         match self.read_from_io() {
@@ -88,8 +85,17 @@ impl<T: Io> Buffered<T> {
 
     fn read_from_io(&mut self) -> io::Result<usize> {
         use bytes::BufMut;
+        self.read_blocked = false;
         unsafe {
-            let n = try!(self.io.read(self.read_buf.bytes_mut()));
+            let n = match self.io.read(self.read_buf.bytes_mut()) {
+                Ok(n) => n,
+                Err(e) => {
+                    if e.kind() == io::ErrorKind::WouldBlock {
+                        self.read_blocked = true;
+                    }
+                    return Err(e)
+                }
+            };
             self.read_buf.advance_mut(n);
             Ok(n)
         }
@@ -112,10 +118,13 @@ impl<T: Io> Buffered<T> {
         self.write_buf.buffer(buf.as_ref())
     }
 
-    #[cfg(test)]
     pub fn io_mut(&mut self) -> &mut T {
         &mut self.io
     }
+
+    pub fn is_read_blocked(&self) -> bool {
+        self.read_blocked
+    }
 }
 
 impl<T: Write> Write for Buffered<T> {
@@ -146,17 +155,17 @@ pub trait MemRead {
     fn read_mem(&mut self, len: usize) -> io::Result<Bytes>;
 }
 
-impl<T: Io> MemRead for Buffered<T> {
+impl<T: AsyncRead + AsyncWrite> MemRead for Buffered<T> {
     fn read_mem(&mut self, len: usize) -> io::Result<Bytes> {
         trace!("Buffered.read_mem read_buf={}, wanted={}", self.read_buf.len(), len);
         if !self.read_buf.is_empty() {
             let n = ::std::cmp::min(len, self.read_buf.len());
             trace!("Buffered.read_mem read_buf is not empty, slicing {}", n);
-            Ok(self.read_buf.drain_to(n).freeze())
+            Ok(self.read_buf.split_to(n).freeze())
         } else {
             self.reserve_read_buf();
             let n = try!(self.read_from_io());
-            Ok(self.read_buf.drain_to(::std::cmp::min(len, n)).freeze())
+            Ok(self.read_buf.split_to(::std::cmp::min(len, n)).freeze())
         }
     }
 }

src/lib.rs

@@ -21,10 +21,10 @@ extern crate httparse;
 #[cfg_attr(test, macro_use)] extern crate language_tags;
 #[macro_use] extern crate log;
 #[macro_use] pub extern crate mime;
-extern crate relay;
 extern crate base64;
 extern crate time;
 #[macro_use] extern crate tokio_core as tokio;
+extern crate tokio_io;
 extern crate tokio_proto;
 extern crate tokio_service;
 extern crate unicase;

src/mock.rs

@@ -1,8 +1,8 @@
 use std::cmp;
 use std::io::{self, Read, Write};
 
-use futures::Async;
+use futures::Poll;
-use tokio::io::Io;
+use tokio_io::{AsyncRead, AsyncWrite};
 
 #[derive(Debug)]
 pub struct Buf {
@@ -123,21 +123,12 @@ impl<T: Write> Write for AsyncIo<T> {
     }
 }
 
-impl<T: Read + Write> Io for AsyncIo<T> {
+impl<T: Read + Write> AsyncRead for AsyncIo<T> {
-    fn poll_read(&mut self) -> Async<()> {
-        if self.bytes_until_block == 0 {
-            Async::NotReady
-        } else {
-            Async::Ready(())
-        }
 }
 
-    fn poll_write(&mut self) -> Async<()> {
+impl<T: Read + Write> AsyncWrite for AsyncIo<T> {
-        if self.bytes_until_block == 0 {
+    fn shutdown(&mut self) -> Poll<(), io::Error> {
-            Async::NotReady
+        Ok(().into())
-        } else {
-            Async::Ready(())
-        }
     }
 }
 

src/server/mod.rs

@@ -13,9 +13,10 @@ use std::time::Duration;
 
 use futures::future;
 use futures::task::{self, Task};
-use futures::{Future, Map, Stream, Poll, Async, Sink, StartSend, AsyncSink};
+use futures::{Future, Stream, Poll, Async, Sink, StartSend, AsyncSink};
+use futures::future::Map;
 
-use tokio::io::Io;
+use tokio_io::{AsyncRead, AsyncWrite};
 use tokio::reactor::{Core, Handle, Timeout};
 use tokio::net::TcpListener;
 use tokio_proto::BindServer;
@@ -124,7 +125,7 @@ impl<B: AsRef<[u8]> + 'static> Http<B> {
                                  service: S)
         where S: Service<Request = Request, Response = Response<Bd>, Error = ::Error> + 'static,
               Bd: Stream<Item=B, Error=::Error> + 'static,
-              I: Io + 'static,
+              I: AsyncRead + AsyncWrite + 'static,
     {
         self.bind_server(handle, io, HttpService {
             inner: service,
@@ -165,7 +166,7 @@ pub struct __ProtoBindTransport<T, B> {
 }
 
 impl<T, B> ServerProto<T> for Http<B>
-where T: Io + 'static,
+    where T: AsyncRead + AsyncWrite + 'static,
           B: AsRef<[u8]> + 'static,
 {
     type Request = __ProtoRequest;
@@ -189,8 +190,8 @@ where T: Io + 'static,
 }
 
 impl<T, B> Sink for __ProtoTransport<T, B>
-where T: Io + 'static,
+    where T: AsyncRead + AsyncWrite + 'static,
-      B: AsRef<[u8]>,
+          B: AsRef<[u8]> + 'static,
 {
     type SinkItem = Frame<__ProtoResponse, B, ::Error>;
     type SinkError = io::Error;
@@ -224,9 +225,16 @@ where T: Io + 'static,
     fn poll_complete(&mut self) -> Poll<(), io::Error> {
         self.0.poll_complete()
     }
+
+    fn close(&mut self) -> Poll<(), io::Error> {
+        self.0.close()
+    }
 }
 
-impl<T: Io + 'static, B: AsRef<[u8]>> Stream for __ProtoTransport<T, B> {
+impl<T, B> Stream for __ProtoTransport<T, B>
+    where T: AsyncRead + AsyncWrite + 'static,
+          B: AsRef<[u8]> + 'static,
+{
     type Item = Frame<__ProtoRequest, http::Chunk, ::Error>;
     type Error = io::Error;
 
@@ -246,7 +254,10 @@ impl<T: Io + 'static, B: AsRef<[u8]>> Stream for __ProtoTransport<T, B> {
     }
 }
 
-impl<T: Io + 'static, B: AsRef<[u8]> + 'static> Transport for __ProtoTransport<T, B> {
+impl<T, B> Transport for __ProtoTransport<T, B>
+    where T: AsyncRead + AsyncWrite + 'static,
+          B: AsRef<[u8]> + 'static,
+{
     fn tick(&mut self) {
         self.0.tick()
     }
@@ -256,7 +267,9 @@ impl<T: Io + 'static, B: AsRef<[u8]> + 'static> Transport for __ProtoTransport<T
     }
 }
 
-impl<T: Io + 'static, B> Future for __ProtoBindTransport<T, B> {
+impl<T, B> Future for __ProtoBindTransport<T, B>
+    where T: AsyncRead + AsyncWrite + 'static,
+{
     type Item = __ProtoTransport<T, B>;
     type Error = io::Error;