rt: add missing Send bound (#3089)

4 files changed, 6 insertions, 1 deletions

diff --git a/tokio/src/runtime/blocking/pool.rs b/tokio/src/runtime/blocking/pool.rs
index 2967a109..6b9fb1bf 100644
--- a/tokio/src/runtime/blocking/pool.rs
+++ b/tokio/src/runtime/blocking/pool.rs
@@ -70,6 +70,7 @@ const KEEP_ALIVE: Duration = Duration::from_secs(10);
 pub(crate) fn spawn_blocking<F, R>(func: F) -> JoinHandle<R>
 where
     F: FnOnce() -> R + Send + 'static,
+    R: Send + 'static,
 {
     let rt = context::current().expect("not currently running on the Tokio runtime.");
     rt.spawn_blocking(func)
@@ -79,6 +80,7 @@ where
 pub(crate) fn try_spawn_blocking<F, R>(func: F) -> Result<(), ()>
 where
     F: FnOnce() -> R + Send + 'static,
+    R: Send + 'static,
 {
     let rt = context::current().expect("not currently running on the Tokio runtime.");
 
diff --git a/tokio/src/runtime/blocking/task.rs b/tokio/src/runtime/blocking/task.rs
index a521af46..ee2d8d6d 100644
--- a/tokio/src/runtime/blocking/task.rs
+++ b/tokio/src/runtime/blocking/task.rs
@@ -19,7 +19,8 @@ impl<T> Unpin for BlockingTask<T> {}
 
 impl<T, R> Future for BlockingTask<T>
 where
-    T: FnOnce() -> R,
+    T: FnOnce() -> R + Send + 'static,
+    R: Send + 'static,
 {
     type Output = R;
 
diff --git a/tokio/src/runtime/handle.rs b/tokio/src/runtime/handle.rs
index c9ffd5cd..72b9c065 100644
--- a/tokio/src/runtime/handle.rs
+++ b/tokio/src/runtime/handle.rs
@@ -45,6 +45,7 @@ impl Handle {
     pub(crate) fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R>
     where
         F: FnOnce() -> R + Send + 'static,
+        R: Send + 'static,
     {
         #[cfg(feature = "tracing")]
         let func = {
diff --git a/tokio/src/runtime/mod.rs b/tokio/src/runtime/mod.rs
index c76f5cf6..f85344db 100644
--- a/tokio/src/runtime/mod.rs
+++ b/tokio/src/runtime/mod.rs
@@ -392,6 +392,7 @@ cfg_rt! {
         pub fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R>
         where
             F: FnOnce() -> R + Send + 'static,
+            R: Send + 'static,
         {
             self.handle.spawn_blocking(func)
         }