tyConsOfType ty
| Just ty' <- coreView ty = tyConsOfType ty'
tyConsOfType (TyVarTy v) = emptyUniqSet
-tyConsOfType (TyConApp tc tys) = tyConsOfTypes tys `addOneToUniqSet` tc
+tyConsOfType (TyConApp tc tys) = extend (tyConsOfTypes tys)
+ where
+ extend | isUnLiftedTyCon tc
+ || isTupleTyCon tc = id
+
+ | otherwise = (`addOneToUniqSet` tc)
+
tyConsOfType (AppTy a b) = tyConsOfType a `unionUniqSets` tyConsOfType b
tyConsOfType (FunTy a b) = (tyConsOfType a `unionUniqSets` tyConsOfType b)
`addOneToUniqSet` funTyCon