Implement TryFrom to transform various I/O primitives into their mio counterparts (#1158)

* `TryFrom<TcpListener> for mio::net::TcpListener`
* `TryFrom<TcpStream> for mio::net::TcpStream`
* `TryFrom<UdpSocket> for mio::net::UdpSocket`
* `TryFrom<UnixListener> for mio_uds::UnixListener`
* `TryFrom<UnixStream> for mio_uds::UnixStream`

tokio-tcp/src/listener.rs

@@ -2,6 +2,7 @@
 use super::incoming::Incoming;
 use super::TcpStream;
 use mio;
+use std::convert::TryFrom;
 use std::fmt;
 use std::io;
 use std::net::{self, SocketAddr};
@@ -313,6 +314,18 @@ impl TcpListener {
     }
 }
 
+impl TryFrom<TcpListener> for mio::net::TcpListener {
+    type Error = io::Error;
+
+    /// Consumes value, returning the mio I/O object.
+    ///
+    /// See [`tokio_reactor::PollEvented::into_inner`] for more details about
+    /// resource deregistration that happens during the call.
+    fn try_from(value: TcpListener) -> Result<Self, Self::Error> {
+        value.io.into_inner()
+    }
+}
+
 impl fmt::Debug for TcpListener {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.io.get_ref().fmt(f)

tokio-tcp/src/stream.rs

@@ -1,6 +1,7 @@
 use bytes::{Buf, BufMut};
 use iovec::IoVec;
 use mio;
+use std::convert::TryFrom;
 use std::fmt;
 use std::future::Future;
 use std::io;
@@ -709,6 +710,18 @@ impl TcpStream {
     }
 }
 
+impl TryFrom<TcpStream> for mio::net::TcpStream {
+    type Error = io::Error;
+
+    /// Consumes value, returning the mio I/O object.
+    ///
+    /// See [`tokio_reactor::PollEvented::into_inner`] for more details about
+    /// resource deregistration that happens during the call.
+    fn try_from(value: TcpStream) -> Result<Self, Self::Error> {
+        value.io.into_inner()
+    }
+}
+
 // ===== impl Read / Write =====
 
 impl AsyncRead for TcpStream {