Default associated type family gets deleted

[jmcarthur]

Problem

Running hindent on a class that includes a default associated type family has the effect of deleting the default.

• [X] I checked the issue tracker for existing issues about this problem.
• [X] I'm using the latest version of hindent. (built straight from Github)

Input haskell

class Foo a where
  type Bar a
  type instance Bar a = ()

Expected output haskell

class Foo a where
  type Bar a
  type instance Bar a = ()

Actual output haskell

class Foo a where
  type Bar a