Use TypeOperators language pragma

Author: erikd

tests/properties/Properties.hs

@@ -1,4 +1,7 @@
-{-# LANGUAGE RankNTypes, FlexibleContexts, GADTs #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE TypeOperators #-}
 
 module Properties where