doc: add more doc_cfg annotations (#1821)

Also makes the `tokio::net::{tcp, udp, unix}` modules only for "utility"
types. The primary types are in `tokio::net` directly.

4 files changed, 25 insertions, 22 deletions

diff --git a/tokio/src/net/unix/datagram.rs b/tokio/src/net/unix/datagram.rs
index eb8bfe4c..ae1372f6 100644
--- a/tokio/src/net/unix/datagram.rs
+++ b/tokio/src/net/unix/datagram.rs
@@ -10,9 +10,11 @@ use std::os::unix::net::{self, SocketAddr};
 use std::path::Path;
 use std::task::{Context, Poll};
 
-/// An I/O object representing a Unix datagram socket.
-pub struct UnixDatagram {
-    io: PollEvented<mio_uds::UnixDatagram>,
+cfg_uds! {
+    /// An I/O object representing a Unix datagram socket.
+    pub struct UnixDatagram {
+        io: PollEvented<mio_uds::UnixDatagram>,
+    }
 }
 
 impl UnixDatagram {
diff --git a/tokio/src/net/unix/listener.rs b/tokio/src/net/unix/listener.rs
index 7791b05f..5f4787ec 100644
--- a/tokio/src/net/unix/listener.rs
+++ b/tokio/src/net/unix/listener.rs
@@ -12,9 +12,11 @@ use std::os::unix::net::{self, SocketAddr};
 use std::path::Path;
 use std::task::{Context, Poll};
 
-/// A Unix socket which can accept connections from other Unix sockets.
-pub struct UnixListener {
-    io: PollEvented<mio_uds::UnixListener>,
+cfg_uds! {
+    /// A Unix socket which can accept connections from other Unix sockets.
+    pub struct UnixListener {
+        io: PollEvented<mio_uds::UnixListener>,
+    }
 }
 
 impl UnixListener {
diff --git a/tokio/src/net/unix/mod.rs b/tokio/src/net/unix/mod.rs
index 1ec6fa8e..ddba60d1 100644
--- a/tokio/src/net/unix/mod.rs
+++ b/tokio/src/net/unix/mod.rs
@@ -1,21 +1,18 @@
-//! Unix Domain Sockets for Tokio.
-//!
-//! This crate provides APIs for using Unix Domain Sockets with Tokio.
+//! Unix domain socket utility types
 
-mod datagram;
-pub use datagram::UnixDatagram;
+pub(crate) mod datagram;
 
 mod incoming;
 pub use incoming::Incoming;
 
-mod listener;
-pub use listener::UnixListener;
+pub(crate) mod listener;
+pub(crate) use listener::UnixListener;
 
 mod split;
 pub use split::{ReadHalf, WriteHalf};
 
-mod stream;
-pub use stream::UnixStream;
+pub(crate) mod stream;
+pub(crate) use stream::UnixStream;
 
 mod ucred;
 pub use ucred::UCred;
diff --git a/tokio/src/net/unix/stream.rs b/tokio/src/net/unix/stream.rs
index a430fa17..5151b08a 100644
--- a/tokio/src/net/unix/stream.rs
+++ b/tokio/src/net/unix/stream.rs
@@ -14,13 +14,15 @@ use std::path::Path;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
-/// A structure representing a connected Unix socket.
-///
-/// This socket can be connected directly with `UnixStream::connect` or accepted
-/// from a listener with `UnixListener::incoming`. Additionally, a pair of
-/// anonymous Unix sockets can be created with `UnixStream::pair`.
-pub struct UnixStream {
-    io: PollEvented<mio_uds::UnixStream>,
+cfg_uds! {
+    /// A structure representing a connected Unix socket.
+    ///
+    /// This socket can be connected directly with `UnixStream::connect` or accepted
+    /// from a listener with `UnixListener::incoming`. Additionally, a pair of
+    /// anonymous Unix sockets can be created with `UnixStream::pair`.
+    pub struct UnixStream {
+        io: PollEvented<mio_uds::UnixStream>,
+    }
 }
 
 impl UnixStream {