From b0d2bd20eb40b9cbc2958b981ba2dcd9e6f9396e Mon Sep 17 00:00:00 2001
From: 2ndTaleStudio <43264484+2ndTaleStudio@users.noreply.github.com>
Date: Mon, 16 Nov 2020 21:32:29 +0100
Subject: [PATCH] fix soundness

---
 src/lib.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index d36df5d..82ce57a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -81,8 +81,10 @@ pub struct Singleton<T: 'static> {
 
 // The Singleton need to implement Send & Sync to ensure cross core compile check mechanics
 // this is safe as the inner RWLock ensures cross core safety
-unsafe impl<T> Sync for Singleton<T> {}
-unsafe impl<T> Send for Singleton<T> {}
+// but we need to be conditional on the inner type to prevent interior mutable types beeing used
+// inside a singleton
+unsafe impl<T> Sync for Singleton<T> where T: Sync {}
+unsafe impl<T> Send for Singleton<T> where T: Send {}
 
 impl<T: 'static> Singleton<T> {
     /// Create a new [Singleton] instance to be used in a static variable. Only ``const fn`` constructors are allowed