From 159c422afa1a3b0764d931c82c1d58c73b535567 Mon Sep 17 00:00:00 2001
From: Michal 'vorner' Vaner <vorner@vorner.cz>
Date: Fri, 30 Aug 2019 11:59:52 +0200
Subject: [PATCH] Make the OnFlushCancel Send and Sync

It is useless otherwise in most multithreaded applications.
---
 src/core/attributes.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/core/attributes.rs b/src/core/attributes.rs
index 9663c07..2b6c903 100755
--- a/src/core/attributes.rs
+++ b/src/core/attributes.rs
@@ -140,7 +140,7 @@ pub struct ObserveWhen<'a, T, F> {
 static ID_GENERATOR: AtomicUsize = AtomicUsize::new(0);
 
 /// A handle to cancel a flush observer.
-pub struct OnFlushCancel(Arc<dyn Fn()>);
+pub struct OnFlushCancel(Arc<dyn Fn() + Send + Sync>);
 
 impl Cancel for OnFlushCancel {
     fn cancel(&self) {