let rec merge_impl = fun base override =>
  if (std.typeof base) == "record" && (std.typeof override) == "record" then
    let base_fields = std.record.fields base in
    base_fields |> std.array.fold_left
      (fun acc key =>
        let base_value = base |> std.record.get key in
        if std.record.has_field key override then
          let override_value = override |> std.record.get key in
          acc |> std.record.insert key override_value
        else
          acc |> std.record.insert key base_value
      )
      {}
  else
    override
in

{ merge = merge_impl }