Simplify loop in visit_items_with_reordering

Author: camsteffen

src/reorder.rs

@@ -305,25 +305,21 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
     /// Visits and format the given items. Items are reordered If they are
     /// consecutive and reorderable.
     pub(crate) fn visit_items_with_reordering(&mut self, mut items: &[&ast::Item]) {
-        while !items.is_empty() {
+        while let [head, tail @ ..] = items {
             // If the next item is a `use`, `extern crate` or `mod`, then extract it and any
             // subsequent items that have the same item kind to be reordered within
             // `walk_reorderable_items`. Otherwise, just format the next item for output.
-            let item_kind = ReorderableItemKind::from(items[0]);
+            let item_kind = ReorderableItemKind::from(head);
             if item_kind.is_reorderable(self.config) || item_kind.is_regroupable(self.config) {
                 let visited_items_num = self.walk_reorderable_or_regroupable_items(
                     items,
                     item_kind,
                     item_kind.in_group(self.config),
                 );
-                let (_, rest) = items.split_at(visited_items_num);
-                items = rest;
+                (_, items) = items.split_at(visited_items_num);
             } else {
-                // Reaching here means items were not reordered. There must be at least
-                // one item left in `items`, so calling `unwrap()` here is safe.
-                let (item, rest) = items.split_first().unwrap();
-                self.visit_item(item);
-                items = rest;
+                self.visit_item(head);
+                items = tail;
             }
         }
     }