def test_fields_mismatch(self):
        instr = pyrtl.WireVector(name='instr', bitwidth=32)
        with self.assertRaises(pyrtl.PyrtlError):
            o = pyrtl.chop(instr, 10, 10, 10)
        with self.assertRaises(pyrtl.PyrtlError):
            o = pyrtl.chop(instr, 10, 10, 14)
        with self.assertRaises(pyrtl.PyrtlError):
            o = pyrtl.chop(instr, 33)