Module type and intellisense looks weird after functor

1

I’m using functors to generate validated primitive types, like a NonNegativeInt. It works. But the tooltip/intellisense for using the functor is kind of strange. For example, in the code below when I try to use my NonNegativeInt method here is what I see…

image

What I want to see is int instead of C.domain. At this point, what is module C? If I want all traces of C.domain to be replaced with int I think I need to do the BetterNonNegativeInt casting/assignment below, which is an extra step. Is there some way to do all this in a single step? Is this a problem with the VS Code extension?

module type T = {
  type t
  type domain
  let eq: (t, t) => bool
  let make: domain => option<t>
  let value: t => domain
}

module type Configuration = {
  type domain
  let cmp: (domain, domain) => float
  let validate: domain => option<domain>
}

module Make = (C: Configuration): (T with type domain := C.domain) => {
  type t = C.domain
  type domain = C.domain
  let eq = (i: t, j: t) => C.cmp(i, j) === 0.0
  let value = i => i
  let make = (i: domain) => C.validate(i)
}

module NonNegativeInt = Make({
  type domain = int
  let cmp = (x, y) => x < y ? -1.0 : x > y ? 1.0 : 0.0
  let validate = i => i >= 0 ? Some(i) : None
})

module BetterNonNegativeInt: T with type domain := int = NonNegativeInt
2

These kinds of issues are better to post on the issue tracker for the VSCode extension rather than on the forums.

3

Ok no problem. I just wasn’t sure if there was something wrong or whether I’m not understanding how functors work.

4

I made a post on that github issue you opened adding some screenshots for context.

But if you want a quick fix (and someone reading this thread is interested), you can write your NonNegativeInt module like this:

module NonNegativeInt: T with type domain := int = Make({
  type domain = int
  let cmp = (x, y) => x < y ? -1.0 : x > y ? 1.0 : 0.0
  let validate = i => i >= 0 ? Some(i) : None
})

with the explicit signature there and you will get the correct type hits and signatures.