Parse Error on empty closed type families

[JakobBruenker]

GHC parses the following file just fine, but using haskell-src-exts' parseFile results in a Parse Error:

{-# LANGUAGE TypeFamilies #-}

type family Test where

If you add a line like

  Test = ()

To the end of this file, parseFile works.

Empty closed type families can be useful when the return type is void, as in

{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeOperators #-}

import Data.Type.Equality
import Data.Void

type family OneIsn'tZero (p :: 1 :~: 0) :: Void where

This is also how I encountered this bug.

This might be related to #358

Version: Both 1.21.0 on hackage and the master branch.