Wrong functions clojure js output that couses runtime error

1

I have a function that returns another function. At first I’ve written it like this:

type baz = {foo: option<bool>}
type bar = unit => baz
let make = (): bar => {
  () => {
    {
      foo: None,
    }
  }
}

The make function has a type unit => bar which is correct.
After this I had to spend a bunch of time (partially because I haven’t written tests for this part) trying to figure out why the Curry helper didn’t work properly in js output before I’ve noticed that the module’ve been transpiled into this:

function make(param, param$1) {
  return {
          foo: undefined
        };
}

export {
  make ,
  
}

Just a function that imediatly returns a result.
I’ve rewritten my module to this, that helped with the problem, but still it wasn’t a good experience debugging the error.

type baz = {foo: option<bool>}
type bar = unit => baz
let make = () => {
  let bar: bar = () => {
    {
      foo: None,
    }
  }
  bar
}

On the rescript side the make’s type in both cases was correct.

2

Is it possible you could leverage the “uncurry” syntax to make it work with an example closer to your original?

3

This works as expected. Only uncurried calling convention are guaranteed to keep the arity when compiling to JS. For curried function, the compiler has the freedom to do such optimizations

4

Here is a full example:

type baz = {foo: option<bool>}
type bar = (.unit) => baz

let make = (): bar => {
  (.) => {
    {
      foo: None,
    }
  }
}

which compiles to

function make(param) {
  return function () {
    return {
            foo: undefined
          };
  };
}

exports.make = make;

Playground Link