False Positive When Using First Class Module Type Alias

[LTibbetts]

I ran across a case where false positives were being generated for first class modules. In particular the false positive was only generated if a type alias was used for the module's type. I have recreated a minimal reproduction of the issue below. I have already taken one attempt at fixing this myself but it introduced more false positives in our codebase. Any help or pointers would be appreciated!

Example First Class Module

module type ModuleType = {
  type t
}

module MakeWithType = (A: ModuleType): (ModuleType with type t = A.t) => {
  type t = A.t
}

let main = () => {
  let moduleA: module(ModuleType with type t = int) = module(
    MakeWithType({
      type t = int
    })
  )

  let module(A) = moduleA

  let intA: A.t = 1

  Js.log(intA)
}

main()

Example First Class Module with False Positive

module type ModuleType = {
  type t
}

module MakeWithType = (A: ModuleType): (ModuleType with type t = A.t) => {
  type t = A.t
}

type moduleAlias<'a> = module(ModuleType with type t = 'a)

let main = () => {
  // Marked as dead (transitively) due to type alias
  let moduleA: moduleAlias<int> = module(
    MakeWithType({
      type t = int
    })
  )

  // Marked as dead (false positive)
  let module(A) = moduleA

  // Live usage of module A
  let intA: A.t = 1

  Js.log(intA)
}

main()