Fix building docs on Windows

tokio/src/io/mod.rs

@@ -231,6 +231,9 @@ cfg_io_driver_impl! {
     pub(crate) use poll_evented::PollEvented;
 }
 
+// The bsd module can't be build on Windows, so we completely ignore it, even
+// when building documentation.
+#[cfg(unix)]
 cfg_aio! {
     /// BSD-specific I/O types.
     pub mod bsd {

tokio/src/net/tcp/socket.rs

@@ -787,6 +787,9 @@ impl fmt::Debug for TcpSocket {
     }
 }
 
+// These trait implementations can't be build on Windows, so we completely
+// ignore them, even when building documentation.
+#[cfg(unix)]
 cfg_unix! {
     impl AsRawFd for TcpSocket {
         fn as_raw_fd(&self) -> RawFd {

tokio/src/signal/windows.rs

@@ -12,13 +12,15 @@ use crate::signal::RxFuture;
 use std::io;
 use std::task::{Context, Poll};
 
-#[cfg(not(docsrs))]
+#[cfg(windows)]
 #[path = "windows/sys.rs"]
 mod imp;
-#[cfg(not(docsrs))]
+
+#[cfg(windows)]
 pub(crate) use self::imp::{OsExtraData, OsStorage};
 
-#[cfg(docsrs)]
+// For building documentation on Unix machines when the `docsrs` flag is set.
+#[cfg(not(windows))]
 #[path = "windows/stub.rs"]
 mod imp;