test: add Send/Sync tests for all async fns (#2377)

Also updates Empty and Pending to be unconditionally Send and Sync.

3 files changed, 223 insertions, 0 deletions

diff --git a/tokio/src/stream/empty.rs b/tokio/src/stream/empty.rs
index a320d44b..6118673e 100644
--- a/tokio/src/stream/empty.rs
+++ b/tokio/src/stream/empty.rs
@@ -10,6 +10,8 @@ use core::task::{Context, Poll};
 pub struct Empty<T>(PhantomData<T>);
 
 impl<T> Unpin for Empty<T> {}
+unsafe impl<T> Send for Empty<T> {}
+unsafe impl<T> Sync for Empty<T> {}
 
 /// Creates a stream that yields nothing.
 ///
diff --git a/tokio/src/stream/pending.rs b/tokio/src/stream/pending.rs
index abc38c44..2e06a1c2 100644
--- a/tokio/src/stream/pending.rs
+++ b/tokio/src/stream/pending.rs
@@ -10,6 +10,8 @@ use core::task::{Context, Poll};
 pub struct Pending<T>(PhantomData<T>);
 
 impl<T> Unpin for Pending<T> {}
+unsafe impl<T> Send for Pending<T> {}
+unsafe impl<T> Sync for Pending<T> {}
 
 /// Creates a stream that is never ready
 ///
diff --git a/tokio/tests/async_send_sync.rs b/tokio/tests/async_send_sync.rs
new file mode 100644
index 00000000..f50b41a0
--- /dev/null
+++ b/tokio/tests/async_send_sync.rs
@@ -0,0 +1,219 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use std::cell::Cell;
+use std::io::Cursor;
+use std::net::SocketAddr;
+use std::rc::Rc;
+use tokio::net::TcpStream;
+use tokio::time::{Duration, Instant};
+
+#[allow(dead_code)]
+type BoxFutureSync<T> = std::pin::Pin<Box<dyn std::future::Future<Output = T> + Send + Sync>>;
+#[allow(dead_code)]
+type BoxFutureSend<T> = std::pin::Pin<Box<dyn std::future::Future<Output = T> + Send>>;
+#[allow(dead_code)]
+type BoxFuture<T> = std::pin::Pin<Box<dyn std::future::Future<Output = T>>>;
+
+#[allow(dead_code)]
+fn require_send<T: Send>(_t: &T) {}
+#[allow(dead_code)]
+fn require_sync<T: Sync>(_t: &T) {}
+
+#[allow(dead_code)]
+struct Invalid;
+
+trait AmbiguousIfSend<A> {
+    fn some_item(&self) {}
+}
+impl<T: ?Sized> AmbiguousIfSend<()> for T {}
+impl<T: ?Sized + Send> AmbiguousIfSend<Invalid> for T {}
+
+trait AmbiguousIfSync<A> {
+    fn some_item(&self) {}
+}
+impl<T: ?Sized> AmbiguousIfSync<()> for T {}
+impl<T: ?Sized + Sync> AmbiguousIfSync<Invalid> for T {}
+
+macro_rules! into_todo {
+    ($typ:ty) => {{
+        let x: $typ = todo!();
+        x
+    }};
+}
+macro_rules! async_assert_fn {
+    ($($f:ident $(< $($generic:ty),* > )? )::+($($arg:ty),*): Send & Sync) => {
+        #[allow(unreachable_code)]
+        #[allow(unused_variables)]
+        const _: fn() = || {
+            let f = $($f $(::<$($generic),*>)? )::+( $( into_todo!($arg) ),* );
+            require_send(&f);
+            require_sync(&f);
+        };
+    };
+    ($($f:ident $(< $($generic:ty),* > )? )::+($($arg:ty),*): Send & !Sync) => {
+        #[allow(unreachable_code)]
+        #[allow(unused_variables)]
+        const _: fn() = || {
+            let f = $($f $(::<$($generic),*>)? )::+( $( into_todo!($arg) ),* );
+            require_send(&f);
+            AmbiguousIfSync::some_item(&f);
+        };
+    };
+    ($($f:ident $(< $($generic:ty),* > )? )::+($($arg:ty),*): !Send & Sync) => {
+        #[allow(unreachable_code)]
+        #[allow(unused_variables)]
+        const _: fn() = || {
+            let f = $($f $(::<$($generic),*>)? )::+( $( into_todo!($arg) ),* );
+            AmbiguousIfSend::some_item(&f);
+            require_sync(&f);
+        };
+    };
+    ($($f:ident $(< $($generic:ty),* > )? )::+($($arg:ty),*): !Send & !Sync) => {
+        #[allow(unreachable_code)]
+        #[allow(unused_variables)]
+        const _: fn() = || {
+            let f = $($f $(::<$($generic),*>)? )::+( $( into_todo!($arg) ),* );
+            AmbiguousIfSend::some_item(&f);
+            AmbiguousIfSync::some_item(&f);
+        };
+    };
+}
+
+async_assert_fn!(tokio::io::copy(&mut TcpStream, &mut TcpStream): Send & Sync);
+async_assert_fn!(tokio::io::empty(): Send & Sync);
+async_assert_fn!(tokio::io::repeat(u8): Send & Sync);
+async_assert_fn!(tokio::io::sink(): Send & Sync);
+async_assert_fn!(tokio::io::split(TcpStream): Send & Sync);
+async_assert_fn!(tokio::io::stderr(): Send & Sync);
+async_assert_fn!(tokio::io::stdin(): Send & Sync);
+async_assert_fn!(tokio::io::stdout(): Send & Sync);
+async_assert_fn!(tokio::io::Split<Cursor<Vec<u8>>>::next_segment(_): Send & Sync);
+
+async_assert_fn!(tokio::fs::canonicalize(&str): Send & Sync);
+async_assert_fn!(tokio::fs::copy(&str, &str): Send & Sync);
+async_assert_fn!(tokio::fs::create_dir(&str): Send & Sync);
+async_assert_fn!(tokio::fs::create_dir_all(&str): Send & Sync);
+async_assert_fn!(tokio::fs::hard_link(&str, &str): Send & Sync);
+async_assert_fn!(tokio::fs::metadata(&str): Send & Sync);
+async_assert_fn!(tokio::fs::read(&str): Send & Sync);
+async_assert_fn!(tokio::fs::read_dir(&str): Send & Sync);
+async_assert_fn!(tokio::fs::read_link(&str): Send & Sync);
+async_assert_fn!(tokio::fs::read_to_string(&str): Send & Sync);
+async_assert_fn!(tokio::fs::remove_dir(&str): Send & Sync);
+async_assert_fn!(tokio::fs::remove_dir_all(&str): Send & Sync);
+async_assert_fn!(tokio::fs::remove_file(&str): Send & Sync);
+async_assert_fn!(tokio::fs::rename(&str, &str): Send & Sync);
+async_assert_fn!(tokio::fs::set_permissions(&str, std::fs::Permissions): Send & Sync);
+async_assert_fn!(tokio::fs::symlink_metadata(&str): Send & Sync);
+async_assert_fn!(tokio::fs::write(&str, Vec<u8>): Send & Sync);
+async_assert_fn!(tokio::fs::ReadDir::next_entry(_): Send & Sync);
+async_assert_fn!(tokio::fs::OpenOptions::open(_, &str): Send & Sync);
+async_assert_fn!(tokio::fs::DirEntry::metadata(_): Send & Sync);
+async_assert_fn!(tokio::fs::DirEntry::file_type(_): Send & Sync);
+
+async_assert_fn!(tokio::fs::File::open(&str): Send & Sync);
+async_assert_fn!(tokio::fs::File::create(&str): Send & Sync);
+async_assert_fn!(tokio::fs::File::seek(_, std::io::SeekFrom): Send & Sync);
+async_assert_fn!(tokio::fs::File::sync_all(_): Send & Sync);
+async_assert_fn!(tokio::fs::File::sync_data(_): Send & Sync);
+async_assert_fn!(tokio::fs::File::set_len(_, u64): Send & Sync);
+async_assert_fn!(tokio::fs::File::metadata(_): Send & Sync);
+async_assert_fn!(tokio::fs::File::try_clone(_): Send & Sync);
+async_assert_fn!(tokio::fs::File::into_std(_): Send & Sync);
+async_assert_fn!(tokio::fs::File::set_permissions(_, std::fs::Permissions): Send & Sync);
+
+async_assert_fn!(tokio::net::lookup_host(SocketAddr): Send & Sync);
+async_assert_fn!(tokio::net::TcpListener::bind(SocketAddr): Send & Sync);
+async_assert_fn!(tokio::net::TcpListener::accept(_): Send & Sync);
+async_assert_fn!(tokio::net::TcpStream::connect(SocketAddr): Send & Sync);
+async_assert_fn!(tokio::net::TcpStream::peek(_, &mut [u8]): Send & Sync);
+async_assert_fn!(tokio::net::tcp::ReadHalf::peek(_, &mut [u8]): Send & Sync);
+async_assert_fn!(tokio::net::UdpSocket::bind(SocketAddr): Send & Sync);
+async_assert_fn!(tokio::net::UdpSocket::connect(_, SocketAddr): Send & Sync);
+async_assert_fn!(tokio::net::UdpSocket::send(_, &[u8]): Send & Sync);
+async_assert_fn!(tokio::net::UdpSocket::recv(_, &mut [u8]): Send & Sync);
+async_assert_fn!(tokio::net::UdpSocket::send_to(_, &[u8], SocketAddr): Send & Sync);
+async_assert_fn!(tokio::net::UdpSocket::recv_from(_, &mut [u8]): Send & Sync);
+async_assert_fn!(tokio::net::udp::RecvHalf::recv(_, &mut [u8]): Send & Sync);
+async_assert_fn!(tokio::net::udp::RecvHalf::recv_from(_, &mut [u8]): Send & Sync);
+async_assert_fn!(tokio::net::udp::SendHalf::send(_, &[u8]): Send & Sync);
+async_assert_fn!(tokio::net::udp::SendHalf::send_to(_, &[u8], &SocketAddr): Send & Sync);
+
+#[cfg(unix)]
+mod unix_datagram {
+    use super::*;
+    async_assert_fn!(tokio::net::UnixListener::bind(&str): Send & Sync);
+    async_assert_fn!(tokio::net::UnixListener::accept(_): Send & Sync);
+    async_assert_fn!(tokio::net::UnixDatagram::send(_, &[u8]): Send & Sync);
+    async_assert_fn!(tokio::net::UnixDatagram::recv(_, &mut [u8]): Send & Sync);
+    async_assert_fn!(tokio::net::UnixDatagram::send_to(_, &[u8], &str): Send & Sync);
+    async_assert_fn!(tokio::net::UnixDatagram::recv_from(_, &mut [u8]): Send & Sync);
+    async_assert_fn!(tokio::net::UnixStream::connect(&str): Send & Sync);
+}
+
+async_assert_fn!(tokio::process::Child::wait_with_output(_): Send & Sync);
+async_assert_fn!(tokio::signal::ctrl_c(): Send & Sync);
+#[cfg(unix)]
+async_assert_fn!(tokio::signal::unix::Signal::recv(_): Send & Sync);
+
+async_assert_fn!(tokio::stream::empty<Rc<u8>>(): Send & Sync);
+async_assert_fn!(tokio::stream::pending<Rc<u8>>(): Send & Sync);
+async_assert_fn!(tokio::stream::iter(std::vec::IntoIter<u8>): Send & Sync);
+
+async_assert_fn!(tokio::sync::Barrier::wait(_): Send & Sync);
+async_assert_fn!(tokio::sync::Mutex<u8>::lock(_): Send & Sync);
+async_assert_fn!(tokio::sync::Mutex<Cell<u8>>::lock(_): Send & Sync);
+async_assert_fn!(tokio::sync::Mutex<Rc<u8>>::lock(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::Notify::notified(_): Send & !Sync);
+async_assert_fn!(tokio::sync::RwLock<u8>::read(_): Send & Sync);
+async_assert_fn!(tokio::sync::RwLock<u8>::write(_): Send & Sync);
+async_assert_fn!(tokio::sync::RwLock<Cell<u8>>::read(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::RwLock<Cell<u8>>::write(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::RwLock<Rc<u8>>::read(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::RwLock<Rc<u8>>::write(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::Semaphore::acquire(_): Send & Sync);
+
+async_assert_fn!(tokio::sync::broadcast::Receiver<u8>::recv(_): Send & Sync);
+async_assert_fn!(tokio::sync::broadcast::Receiver<Cell<u8>>::recv(_): Send & Sync);
+async_assert_fn!(tokio::sync::broadcast::Receiver<Rc<u8>>::recv(_): !Send & !Sync);
+
+async_assert_fn!(tokio::sync::mpsc::Receiver<u8>::recv(_): Send & Sync);
+async_assert_fn!(tokio::sync::mpsc::Receiver<Cell<u8>>::recv(_): Send & Sync);
+async_assert_fn!(tokio::sync::mpsc::Receiver<Rc<u8>>::recv(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::mpsc::Sender<u8>::send(_, u8): Send & Sync);
+async_assert_fn!(tokio::sync::mpsc::Sender<Cell<u8>>::send(_, Cell<u8>): Send & !Sync);
+async_assert_fn!(tokio::sync::mpsc::Sender<Rc<u8>>::send(_, Rc<u8>): !Send & !Sync);
+
+async_assert_fn!(tokio::sync::mpsc::UnboundedReceiver<u8>::recv(_): Send & Sync);
+async_assert_fn!(tokio::sync::mpsc::UnboundedReceiver<Cell<u8>>::recv(_): Send & Sync);
+async_assert_fn!(tokio::sync::mpsc::UnboundedReceiver<Rc<u8>>::recv(_): !Send & !Sync);
+
+async_assert_fn!(tokio::sync::watch::Receiver<u8>::recv(_): Send & Sync);
+async_assert_fn!(tokio::sync::watch::Receiver<Cell<u8>>::recv(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::watch::Receiver<Rc<u8>>::recv(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::watch::Sender<u8>::closed(_): Send & Sync);
+async_assert_fn!(tokio::sync::watch::Sender<Cell<u8>>::closed(_): !Send & !Sync);
+async_assert_fn!(tokio::sync::watch::Sender<Rc<u8>>::closed(_): !Send & !Sync);
+
+async_assert_fn!(tokio::task::LocalKey<u32>::scope(_, u32, BoxFutureSync<()>): Send & Sync);
+async_assert_fn!(tokio::task::LocalKey<u32>::scope(_, u32, BoxFutureSend<()>): Send & !Sync);
+async_assert_fn!(tokio::task::LocalKey<u32>::scope(_, u32, BoxFuture<()>): !Send & !Sync);
+async_assert_fn!(tokio::task::LocalKey<Cell<u32>>::scope(_, Cell<u32>, BoxFutureSync<()>): Send & !Sync);
+async_assert_fn!(tokio::task::LocalKey<Cell<u32>>::scope(_, Cell<u32>, BoxFutureSend<()>): Send & !Sync);
+async_assert_fn!(tokio::task::LocalKey<Cell<u32>>::scope(_, Cell<u32>, BoxFuture<()>): !Send & !Sync);
+async_assert_fn!(tokio::task::LocalKey<Rc<u32>>::scope(_, Rc<u32>, BoxFutureSync<()>): !Send & !Sync);
+async_assert_fn!(tokio::task::LocalKey<Rc<u32>>::scope(_, Rc<u32>, BoxFutureSend<()>): !Send & !Sync);
+async_assert_fn!(tokio::task::LocalKey<Rc<u32>>::scope(_, Rc<u32>, BoxFuture<()>): !Send & !Sync);
+async_assert_fn!(tokio::task::LocalSet::run_until(_, BoxFutureSync<()>): !Send & !Sync);
+
+async_assert_fn!(tokio::time::advance(Duration): Send & Sync);
+async_assert_fn!(tokio::time::delay_for(Duration): Send & Sync);
+async_assert_fn!(tokio::time::delay_until(Instant): Send & Sync);
+async_assert_fn!(tokio::time::timeout(Duration, BoxFutureSync<()>): Send & Sync);
+async_assert_fn!(tokio::time::timeout(Duration, BoxFutureSend<()>): Send & !Sync);
+async_assert_fn!(tokio::time::timeout(Duration, BoxFuture<()>): !Send & !Sync);
+async_assert_fn!(tokio::time::timeout_at(Instant, BoxFutureSync<()>): Send & Sync);
+async_assert_fn!(tokio::time::timeout_at(Instant, BoxFutureSend<()>): Send & !Sync);
+async_assert_fn!(tokio::time::timeout_at(Instant, BoxFuture<()>): !Send & !Sync);
+async_assert_fn!(tokio::time::Interval::tick(_): Send & Sync);