Typescript Generation: Invalid output

[lucasavila00]

import gleam/javascript/promise

pub type Task(a) =
  fn() -> promise.Promise(a)

pub fn main() {
  1
}

compiles to this

import * as promise from "../../gleam_javascript/dist/gleam/javascript/promise.d.ts";

export type Task = () => promise.Promise$<RC>;

export function main(): number;

where RC does not exist.

[lpil]

Thank you