Make Send + Sync bounds conditional (fixes #8)

Author: udoprog

src/lib.rs

@@ -377,8 +377,8 @@ where
     _marker: marker::PhantomData<S>,
 }
 
-unsafe impl<T, S> Send for Unordered<T, S> where S: Sentinel {}
-unsafe impl<T, S> Sync for Unordered<T, S> where S: Sentinel {}
+unsafe impl<T, S> Send for Unordered<T, S> where S: Send + Sentinel {}
+unsafe impl<T, S> Sync for Unordered<T, S> where S: Sync + Sentinel {}
 
 impl<T, S> Unpin for Unordered<T, S> where S: Sentinel {}
 

src/pin_slab.rs

@@ -40,8 +40,8 @@ pub struct PinSlab<T> {
     next: usize,
 }
 
-unsafe impl<T> Send for PinSlab<T> {}
-unsafe impl<T> Sync for PinSlab<T> {}
+unsafe impl<T> Send for PinSlab<T> where T: Send {}
+unsafe impl<T> Sync for PinSlab<T> where T: Sync {}
 
 enum Entry<T> {
     // Each slot is pre-allocated with entries of `None`.