From 5d79c638f472344824079469f676468e23e8af2d Mon Sep 17 00:00:00 2001
From: David Pedersen <david.pdrsn@gmail.com>
Date: Tue, 21 Dec 2021 11:17:56 +0100
Subject: [PATCH] Require `Output = ()` on `WebSocketStream::on_upgrade` (#646)

Fixes https://github.com/tokio-rs/axum/issues/636
---
 axum/CHANGELOG.md      | 4 +++-
 axum/src/extract/ws.rs | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/axum/CHANGELOG.md b/axum/CHANGELOG.md
index 592e319d..0362b501 100644
--- a/axum/CHANGELOG.md
+++ b/axum/CHANGELOG.md
@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 # Unreleased
 
-- None.
+- **breaking:** Require `Output = ()` on `WebSocketStream::on_upgrade` ([#644])
+
+[#644]: https://github.com/tokio-rs/axum/pull/644
 
 # 0.4.4 (13. January, 2021)
 
diff --git a/axum/src/extract/ws.rs b/axum/src/extract/ws.rs
index 880ab1e2..235fe6d6 100644
--- a/axum/src/extract/ws.rs
+++ b/axum/src/extract/ws.rs
@@ -201,7 +201,7 @@ impl WebSocketUpgrade {
     pub fn on_upgrade<F, Fut>(self, callback: F) -> Response
     where
         F: FnOnce(WebSocket) -> Fut + Send + 'static,
-        Fut: Future + Send + 'static,
+        Fut: Future<Output = ()> + Send + 'static,
     {
         let on_upgrade = self.on_upgrade;
         let config = self.config;