Operator.createOperator(arg, ops, mc);
assertEquals(1, ops.size());
assertTrue(ops.iterator().next().getMapping() instanceof ListDequotation);
// the nil RippleList --> ListDequotation
arg = mc.list();
ops.clear();
Operator.createOperator(arg, ops, mc);
assertEquals(1, ops.size());
assertTrue(ops.iterator().next().getMapping() instanceof ListDequotation);