TS Enum representation

Main.js

"use strict"

exports.x = 15
exports.y = 16

const numberSyntax = 15
exports.numberSyntax = numberSyntax
const stringSyntax = 16
exports.stringSyntax = stringSyntax

const isMatchImpl = function (x, y) {
    return x === y
}
exports.isMatchImpl = isMatchImpl

const matchImpl = function (matchNumber, matchString, input) {
    if (isMatchImpl(input, numberSyntax)) {
        return matchNumber(input)
    } else {
        if (isMatchImpl(input, stringSyntax)) {
            return matchString(input)
        } else {
            return undefined
        }
    }
}
exports.matchImpl = matchImpl

Main.purs

module Main where

import Prelude
import Data.Function.Uncurried (Fn2, Fn3, runFn2, runFn3)
import Debug (spy)
import Effect (Effect)
import Effect.Class.Console (log, logShow)

data SyntaxEnum
foreign import data NumberSyntax :: SyntaxEnum
foreign import data StringSyntax :: SyntaxEnum

data Syntax :: SyntaxEnum -> Type
data Syntax k

foreign import numberSyntax :: Syntax NumberSyntax
foreign import stringSyntax :: Syntax StringSyntax

foreign import isMatchImpl :: forall s. Fn2 SyntaxEnum (Syntax s) Boolean

isMatch :: forall s. SyntaxEnum -> Syntax s -> Boolean
isMatch = runFn2 isMatchImpl

foreign import matchImpl ::
  forall output.
  Fn3
    (Syntax NumberSyntax -> output)
    (Syntax StringSyntax -> output)
    SyntaxEnum
    output

match :: forall output. (Syntax NumberSyntax -> output) -> (Syntax StringSyntax -> output) -> SyntaxEnum -> output
match = runFn3 matchImpl

foreign import x :: SyntaxEnum
foreign import y :: SyntaxEnum

type Node
  = { kind :: Syntax StringSyntax
    }

n :: Node
n =
  { kind: stringSyntax -- numberSyntax results in error
  }

main :: Effect Unit
main = do
  let
    _ = spy "x" x
    _ = spy "y" y
  logShow $ isMatch x numberSyntax
  logShow $ isMatch x stringSyntax
  logShow $ isMatch y numberSyntax
  logShow $ isMatch y stringSyntax
  let
    f = match (const "Got a number") (const "Got a string")
  log $ f x
  log $ f y
  pure unit

Typescript enums documentation: https://www.typescriptlang.org/docs/handbook/enums.html