net: add UnwindSafe impl to PollEvented (#4384)

tokio/src/io/poll_evented.rs

@@ -4,6 +4,7 @@ use mio::event::Source;
 use std::fmt;
 use std::io;
 use std::ops::Deref;
+use std::panic::{RefUnwindSafe, UnwindSafe};
 
 cfg_io_driver! {
     /// Associates an I/O resource that implements the [`std::io::Read`] and/or
@@ -185,6 +186,10 @@ feature! {
     }
 }
 
+impl<E: Source> UnwindSafe for PollEvented<E> {}
+
+impl<E: Source> RefUnwindSafe for PollEvented<E> {}
+
 impl<E: Source> Deref for PollEvented<E> {
     type Target = E;
 

tokio/tests/net_types_unwind.rs

@@ -0,0 +1,32 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use std::panic::{RefUnwindSafe, UnwindSafe};
+
+#[test]
+fn net_types_are_unwind_safe() {
+    is_unwind_safe::<tokio::net::TcpListener>();
+    is_unwind_safe::<tokio::net::TcpSocket>();
+    is_unwind_safe::<tokio::net::TcpStream>();
+    is_unwind_safe::<tokio::net::UdpSocket>();
+}
+
+#[test]
+#[cfg(unix)]
+fn unix_net_types_are_unwind_safe() {
+    is_unwind_safe::<tokio::net::UnixDatagram>();
+    is_unwind_safe::<tokio::net::UnixListener>();
+    is_unwind_safe::<tokio::net::UnixStream>();
+}
+
+#[test]
+#[cfg(windows)]
+fn windows_net_types_are_unwind_safe() {
+    use tokio::net::windows::named_pipe::NamedPipeClient;
+    use tokio::net::windows::named_pipe::NamedPipeServer;
+
+    is_unwind_safe::<NamedPipeClient>();
+    is_unwind_safe::<NamedPipeServer>();
+}
+
+fn is_unwind_safe<T: UnwindSafe + RefUnwindSafe>() {}