1 files changed, 20 insertions, 6 deletions
diff --git a/vendor/sharded-slab/src/lib.rs b/vendor/sharded-slab/src/lib.rs
index e57cf50e2..ea9b66de3 100644
--- a/vendor/sharded-slab/src/lib.rs
+++ b/vendor/sharded-slab/src/lib.rs
@@ -215,8 +215,11 @@ mod page;
 mod shard;
 mod tid;
 
-pub use cfg::{Config, DefaultConfig};
-pub use clear::Clear;
+pub use self::{
+    cfg::{Config, DefaultConfig},
+    clear::Clear,
+    iter::UniqueIter,
+};
 #[doc(inline)]
 pub use pool::Pool;
 
@@ -735,15 +738,26 @@ impl<T, C: cfg::Config> Slab<T, C> {
     }
 
     /// Returns an iterator over all the items in the slab.
+    ///
+    /// Because this iterator exclusively borrows the slab (i.e. it holds an
+    /// `&mut Slab<T>`), elements will not be added or removed while the
+    /// iteration is in progress.
     pub fn unique_iter(&mut self) -> iter::UniqueIter<'_, T, C> {
         let mut shards = self.shards.iter_mut();
-        let shard = shards.next().expect("must be at least 1 shard");
-        let mut pages = shard.iter();
-        let slots = pages.next().and_then(page::Shared::iter);
+
+        let (pages, slots) = match shards.next() {
+            Some(shard) => {
+                let mut pages = shard.iter();
+                let slots = pages.next().and_then(page::Shared::iter);
+                (pages, slots)
+            }
+            None => ([].iter(), None),
+        };
+
         iter::UniqueIter {
             shards,
-            slots,
             pages,
+            slots,
         }
     }
 }