Incorrect type information on hover with async/await

[DZakh]

It happens when there's a compilation error inside of an async/await function. On hover, it shows a type of the async function instead of the hovered value. Works fine with normal functions in the same file.

[DZakh]

The code:

module Promise = Js.Promise2
module Global = Js.Global

@module("uvu") external test: (string, unit => unit) => unit = "test"
@module("uvu") external asyncTest: (string, unit => promise<unit>) => unit = "test"
@module("uvu") @scope("test") external testRun: unit => unit = "run"
module Assert = {
  @module("uvu/assert") external is: ('a, 'a) => unit = "is"
}

asyncTest("[ReScript] redefine act.notify", async () => {
  Act.setNotify((. ()) => {
    Global.setTimeout(() => Act.notify(.), 0)
  })

  let a = Act.make(0)
  let callsRef = ref(0)
  let _ = a->Act.subscribe((. _) => callsRef.contents = callsRef.contents + 1)

  Assert.is(callsRef.contents, 1)

  a->Act.set(123)
  await Promise.resolve()
  Assert.is(callsRef.contents, 1)
  await Promise.make((~resolve, ~reject as _) => {
    Global.setTimeout(() => resolve(. ()), 0)->ignore
  })
  Assert.is(callsRef.contents, 2)
})

testRun()

[cristianoc]

I think the hover shows the type of what's "under the code" which has a type error: the enclosing function.
Not sure it has to do with async/await per se.
In general, when compilation fails, the compiler returns partial type information, of the parts it has typed (even partially).

[hellos3b]

This happens to me too all the time, it makes debugging a little difficult because when there's any kind of error in an async function you can't inspect any other types in the call

When working with records, this breaks intellisense/autocomplete which then makes it hard to fix. I typically find myself needing to flip through modules to find what a field was named

type output = {outDir: string}

let build = async () => {
  Promise.resolve({outDir: "dist"})
}

let serve = outDir => "localhost" ++ outDir

let devServer = async () => {
  let output = await build()
  serve(output.dir) // <-- "dir" instead of "outDir"
}

'a => promise<'a>
The record field dir can't be found.

If it's defined in another module or file, bring it into scope by:
- Prefixing it with said module name: TheModule.dir
- Or specifying its type: let theValue: TheModule.theType = {dir: VALUE}ReScript

[zth]

Something is indeed wrong. We'll be investigating this soon.

[cristianoc]

Can you add a screenshot of the hover when there's the type error without async?

[hellos3b]

Sure, here's the smallest reproducible example with and without async

let test = async () => {
  let x = 0
  x + "y"
}

[cristianoc]

Take a look at this compiler PR which should fix that: #6012
Can be added to the 10.1 compiler version too, so it goes into bug fix release 10.1.3.