1 files changed, 82 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/future/try_join.rs b/third_party/rust/tokio/src/future/try_join.rs
new file mode 100644
index 0000000000..8943f61a1e
--- /dev/null
+++ b/third_party/rust/tokio/src/future/try_join.rs
@@ -0,0 +1,82 @@
+use crate::future::maybe_done::{maybe_done, MaybeDone};
+
+use pin_project_lite::pin_project;
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+pub(crate) fn try_join3<T1, F1, T2, F2, T3, F3, E>(
+    future1: F1,
+    future2: F2,
+    future3: F3,
+) -> TryJoin3<F1, F2, F3>
+where
+    F1: Future<Output = Result<T1, E>>,
+    F2: Future<Output = Result<T2, E>>,
+    F3: Future<Output = Result<T3, E>>,
+{
+    TryJoin3 {
+        future1: maybe_done(future1),
+        future2: maybe_done(future2),
+        future3: maybe_done(future3),
+    }
+}
+
+pin_project! {
+    pub(crate) struct TryJoin3<F1, F2, F3>
+    where
+        F1: Future,
+        F2: Future,
+        F3: Future,
+    {
+        #[pin]
+        future1: MaybeDone<F1>,
+        #[pin]
+        future2: MaybeDone<F2>,
+        #[pin]
+        future3: MaybeDone<F3>,
+    }
+}
+
+impl<T1, F1, T2, F2, T3, F3, E> Future for TryJoin3<F1, F2, F3>
+where
+    F1: Future<Output = Result<T1, E>>,
+    F2: Future<Output = Result<T2, E>>,
+    F3: Future<Output = Result<T3, E>>,
+{
+    type Output = Result<(T1, T2, T3), E>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let mut all_done = true;
+
+        let mut me = self.project();
+
+        if me.future1.as_mut().poll(cx).is_pending() {
+            all_done = false;
+        } else if me.future1.as_mut().output_mut().unwrap().is_err() {
+            return Poll::Ready(Err(me.future1.take_output().unwrap().err().unwrap()));
+        }
+
+        if me.future2.as_mut().poll(cx).is_pending() {
+            all_done = false;
+        } else if me.future2.as_mut().output_mut().unwrap().is_err() {
+            return Poll::Ready(Err(me.future2.take_output().unwrap().err().unwrap()));
+        }
+
+        if me.future3.as_mut().poll(cx).is_pending() {
+            all_done = false;
+        } else if me.future3.as_mut().output_mut().unwrap().is_err() {
+            return Poll::Ready(Err(me.future3.take_output().unwrap().err().unwrap()));
+        }
+
+        if all_done {
+            Poll::Ready(Ok((
+                me.future1.take_output().unwrap().ok().unwrap(),
+                me.future2.take_output().unwrap().ok().unwrap(),
+                me.future3.take_output().unwrap().ok().unwrap(),
+            )))
+        } else {
+            Poll::Pending
+        }
+    }
+}