@Override
  public SelBoolean assignOps(SelOp op, SelType rhs) {
    if (op == SelOp.ASSIGN) {
      SelTypeUtil.checkTypeMatch(this.type(), rhs.type());
      this.val = ((SelBoolean) rhs).val; // direct assignment
      return this;
    }
    throw new UnsupportedOperationException(
        "boolean/Boolean DO NOT support assignment operation " + op);
  }
@Test(expected = UnsupportedOperationException.class)
  public void testInvalidAssignOpType() {
    one.assignOps(SelOp.EQUAL, one);
  }