1 files changed, 49 insertions, 0 deletions
diff --git a/third_party/rust/futures-0.1.31/src/future/flatten.rs b/third_party/rust/futures-0.1.31/src/future/flatten.rs
new file mode 100644
index 0000000000..bfe286975c
--- /dev/null
+++ b/third_party/rust/futures-0.1.31/src/future/flatten.rs
@@ -0,0 +1,49 @@
+use {Future, IntoFuture, Poll};
+use core::fmt;
+use super::chain::Chain;
+
+/// Future for the `flatten` combinator, flattening a future-of-a-future to get just
+/// the result of the final future.
+///
+/// This is created by the `Future::flatten` method.
+#[must_use = "futures do nothing unless polled"]
+pub struct Flatten<A> where A: Future, A::Item: IntoFuture {
+    state: Chain<A, <A::Item as IntoFuture>::Future, ()>,
+}
+
+impl<A> fmt::Debug for Flatten<A>
+    where A: Future + fmt::Debug,
+          A::Item: IntoFuture,
+          <<A as IntoFuture>::Item as IntoFuture>::Future: fmt::Debug,
+{
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("Flatten")
+            .field("state", &self.state)
+            .finish()
+    }
+}
+
+pub fn new<A>(future: A) -> Flatten<A>
+    where A: Future,
+          A::Item: IntoFuture,
+{
+    Flatten {
+        state: Chain::new(future, ()),
+    }
+}
+
+impl<A> Future for Flatten<A>
+    where A: Future,
+          A::Item: IntoFuture,
+          <<A as Future>::Item as IntoFuture>::Error: From<<A as Future>::Error>
+{
+    type Item = <<A as Future>::Item as IntoFuture>::Item;
+    type Error = <<A as Future>::Item as IntoFuture>::Error;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        self.state.poll(|a, ()| {
+            let future = a?.into_future();
+            Ok(Err(future))
+        })
+    }
+}