Prevent the borrow counter from overflowing in Ref::clone

Fixes #33880.
rust-lang · May 30, 2016 · ef60c7c · ef60c7c
1 parent bf9c60c
commit ef60c7c
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
@@ -618,7 +618,9 @@ impl<'b> Clone for BorrowRef<'b> {
         // Since this Ref exists, we know the borrow flag
         // is not set to WRITING.
         let borrow = self.borrow.get();
-        debug_assert!(borrow != WRITING && borrow != UNUSED);
+        debug_assert!(borrow != UNUSED);
+        // Prevent the borrow counter from overflowing.
+        assert!(borrow != WRITING);
         self.borrow.set(borrow + 1);
         BorrowRef { borrow: self.borrow }
     }