Treat optional(_) fields of object types as with records (no conversion JS <-> Reason).

[cristianoc]

This type is a JS object type with a field c of Reason's option type:

[@genType]
type mix = {
  .
  "a": int,
  "b": int,
  "c":
    option({
      .
      "name": string,
      "surname": string,
    }),
};

It can be converted to a JS representation like this:

type mix = {|a:number, b:number, c?:{|name:string, surname:string|}|};

The conversion function can simply be the identity, to allow direct interop without any copying, all while using idiomatic options on the Reason side.

The constraint is on the JS type checking: the type for c ensures that it can not be null, just undefined.

[cristianoc]

This is in release 0.14.0.