[GenType] Generated `Result` type is mismatch with generated js code

[iamchanii]

Hi. I'm using ReScript v11.0.1 and I wrote some code like these:

[Playground Link]

@genType
let parseEnvironment = hostname =>
  switch hostname->String.split(".")->Array.slice(~start=0, ~end=1) {
  | ["xxx", "alpha"] => Ok(#alpha)
  | ["xxx", _] => Ok(#production)
  | _ => Error({"message": "Failed to parse environment"})
  }

@genType
let makeUrl = hostname =>
  switch parseEnvironment(hostname) {
  | Ok(#production) =>
    Ok("https://foo.com/")
  | Ok(#alpha) =>
    Ok("https://alpha.foo.com/")
  | _ =>
    Error({
      "message": "Failed to make url",
      "fallbackUrl": "https://fallback.foo.com/",
    })
  }

// Generated by ReScript, PLEASE EDIT WITH CARE


function parseEnvironment(hostname) {
  var match = hostname.split(".").slice(0, 1);
  if (match.length !== 2) {
    return {
            TAG: "Error",
            _0: {
              message: "Failed to parse environment"
            }
          };
  }
  var match$1 = match[0];
  if (match$1 !== "xxx") {
    return {
            TAG: "Error",
            _0: {
              message: "Failed to parse environment"
            }
          };
  }
  var match$2 = match[1];
  if (match$2 === "alpha") {
    return {
            TAG: "Ok",
            _0: "alpha"
          };
  } else {
    return {
            TAG: "Ok",
            _0: "production"
          };
  }
}

function makeUrl(hostname) {
  var match = parseEnvironment(hostname);
  if (match.TAG !== "Ok") {
    return {
            TAG: "Error",
            _0: {
              message: "Failed to make url",
              fallbackUrl: "https://fallback.foo.com/"
            }
          };
  }
  var match$1 = match._0;
  if (match$1 === "alpha") {
    return {
            TAG: "Ok",
            _0: "https://alpha.foo.com/"
          };
  } else if (match$1 === "production") {
    return {
            TAG: "Ok",
            _0: "https://foo.com/"
          };
  } else {
    return {
            TAG: "Error",
            _0: {
              message: "Failed to make url",
              fallbackUrl: "https://fallback.foo.com/"
            }
          };
  }
}

export {
  parseEnvironment ,
  makeUrl ,
}
/* No side effect */

And genType result is here: (I cannot found something like playground for genType. this is a edited snippet from my work)

export const parseEnvironment: (hostname:string) => 
    { TAG: "Ok"; _0: "alpha" | "production" }
  | { TAG: "Error"; readonly message: string } = AppContextJS.parseEnvironment as any;

export const makeUrl: (hostname:string) => 
    { TAG: "Ok"; _0: string }
  | { TAG: "Error"; readonly fallbackUrl: string; readonly message: string } = AppContextJS.makeUrl as any;

I think the error tag type should be like { TAG: "Error"; _0: { /* ... */ } }.

[cometkim]

@cristianoc Is it intended that the JS obj have an internal representation equivalent to polyvars?

[cristianoc]

GenType hardcodes the definition of result, so there should not be anything special there.
There ought to be a self-contained minimal example that just defines a variant type directly and has a similar issue I guess.

[cristianoc]

I think the issue is that there's currently no way internally in GenType to distinguish between an inline record, and a variant case which has a single payload whose runtime representation is an object.