Unique::next_back: use rev().find_map

Author: Philippe-Cholet

src/unique_impl.rs

@@ -133,14 +133,15 @@ where
     I::Item: Eq + Hash + Clone,
 {
     fn next_back(&mut self) -> Option<Self::Item> {
-        while let Some(v) = self.iter.iter.next_back() {
-            if let Entry::Vacant(entry) = self.iter.used.entry(v) {
+        let UniqueBy { iter, used, .. } = &mut self.iter;
+        iter.rev().find_map(|v| {
+            if let Entry::Vacant(entry) = used.entry(v) {
                 let elt = entry.key().clone();
                 entry.insert(());
                 return Some(elt);
             }
-        }
-        None
+            None
+        })
     }
 }