From 749cc1fd34aeb738ed2e73806cb6b85869f3179e Mon Sep 17 00:00:00 2001
From: chenwei <chenwei_767@qq.com>
Date: Mon, 29 Jun 2020 02:17:15 +0800
Subject: [PATCH] Implement `()` for `Happened` (#6529)

---
 substrate/frame/support/src/traits.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/substrate/frame/support/src/traits.rs b/substrate/frame/support/src/traits.rs
index f25ff67efb..b36559c363 100644
--- a/substrate/frame/support/src/traits.rs
+++ b/substrate/frame/support/src/traits.rs
@@ -329,6 +329,10 @@ pub trait Happened<T> {
 	fn happened(t: &T);
 }
 
+impl<T> Happened<T> for () {
+	fn happened(_: &T) {}
+}
+
 /// A shim for placing around a storage item in order to use it as a `StoredValue`. Ideally this
 /// wouldn't be needed as `StorageValue`s should blanket implement `StoredValue`s, however this
 /// would break the ability to have custom impls of `StoredValue`. The other workaround is to