Using with TypeScript that avoid any

[guyutongxue]

Ohm CLI does not provide very strong type definition. For example, the Node type is something like

interface Node {
    // [...]
    [key: string]: any; // oh-no...
}

That's because when we define an operation or attribute later, they will be usable from every node. So, there is a method -- by extending the Node interface definition -- to provide better programming experience.

// [...] defines MyArg1, MyArg2, MyRetType1, ... that follows your operations/attributes type

declare module "ohm-js" {
  interface Node {
    args: {
      arg1: MyArg1;
      arg2: MyArg2;
    };
    op1(arg1: MyArg1): MyRetType1;
    attr: AttrType;
    op2(arg2: MyArg2): MyRetType2;
  }
}

const op1Dict: MyLangActionDict<MyRetType1> = {
    Node1(_, inner) {
        // here, both op1 and this.args are typed now
        const innerResult = inner.op1(this.args.arg1);
        const attr = inner.attr;
        // [...]
    }
};

semantics.addOperation("op1(arg1)", op1Dict)
    .addAttribute("attr", attrDict)
    .addOperation("op2(arg2)", op2Dict);