def p_case_list(p):
    """
    case_list :
              | CASE expr sep stmt_list_opt case_list
              | CASE expr error stmt_list_opt case_list
              | OTHERWISE stmt_list
    """
    if len(p) == 1:
        p[0] = node.stmt_list()
    elif len(p) == 3:
        assert isinstance(p[2], node.stmt_list)
        p[0] = p[2]
    elif len(p) == 6:
        p[0] = node.if_stmt(
            cond_expr=node.expr(
                op="==", args=node.expr_list([p[2]])),
            then_stmt=p[4],
            else_stmt=p[5])
        p[0].cond_expr.args.append(
            None)  # None will be replaced using backpatch()
    else:
        assert 0