Error on master with async/await and uncurried function

[cknitt]

This code compiles fine with 10.1:

module type Impl = {
  let get: (. string) => Js.Promise.t<string>
}

module Make = (I: Impl) => {
  let get = async key => await I.get(. key)
}

On master, it gives the following error:

  4 │
  5 │ module Make = (I: Impl) => {
  6 │   let get = async key => await I.get(. key)
  7 │ }
  8 │

  This function is a curried function where an uncurried function is expected

(Without async/await, it compiles fine on master, too.)

[cristianoc]

f1 compiles and f2 doesn't:

let next = (. n) => n + 1
let f1 = async () => {
  ()
  next(. 3)
}
let f2 = async () => {
  next(. 3)
}