orphNamesOfCo (TyConAppCo tc cos) = unitNameSet (getName tc) `unionNameSets` orphNamesOfCos cos
orphNamesOfCo (AppCo co1 co2) = orphNamesOfCo co1 `unionNameSets` orphNamesOfCo co2
orphNamesOfCo (ForAllCo _ co) = orphNamesOfCo co
orphNamesOfCo (TyConAppCo tc cos) = unitNameSet (getName tc) `unionNameSets` orphNamesOfCos cos
orphNamesOfCo (AppCo co1 co2) = orphNamesOfCo co1 `unionNameSets` orphNamesOfCo co2
orphNamesOfCo (ForAllCo _ co) = orphNamesOfCo co