Conditional field attributes do not work

[littledivy]

use deno_bindgen::deno_bindgen;

#[deno_bindgen]
pub struct UsbDevice {
  // Not supposed to be serialized or included in typings.
  #[cfg(not(feature = "deno_ffi"))]
  non_serializable_handle: Device,
}

Output:

type UsbDevice = {
  non_serializable_handle: Device, // <-- should not be included
};

Expected output:

type UsbDevice = {};