Typescript types for external types

[vonagam]

Right now this from stdlib:

pub type Map(key, value)

Generates this in ts:

export type Map$<MA, LZ> = any;

Making those descriptions for functions:

export function get<OA, OB>(from: Map$<OA, OB>, get: OA): _.Result<OB, null>;

The same as:

export function get(from: any, get: any): _.Result<any, null>;

So losing most of the gains of typing.

I think it makes sense to have some way to provide typescript type for external js implementation. As an example it can be something like this with existing annotation:

@external(javascript, "../gleam_stdlib.d.ts", "Map")
pub type Map(key, value)

Where instead of generating a type definition of any, an external specified type will be imported and aliased with gleam's expected name. So for Map it will be:

import type {Map as Map$} from "../gleam_stdlib.d.ts"

Thoughts?