在OCaml中，我在AST文件中定义了stmt可以是stmt或stmt List，但是当在函数中使用时，它会报告错误

I defined in AST file that stmt=|stmt|stmt List. Then I have a function with parameter of type stmt, I cannot use stmt List? Can anyone tell me how to make it work?I defined in AST file that stmt=|stmt|stmt List