Formatted file has invalid syntax for the associated type synonym defaults

[lykahb]

Describe the bug Ormolu removes the word "instance" in the output.

To Reproduce Format this file

class IsBoolMap v where
  type Key v
  type instance Key v = Int

  lookupKey :: Key v -> v -> Maybe Bool

The output would be

class IsBoolMap v where
  type Key v
  type Key v = Int  -- Invalid syntax

  lookupKey :: Key v -> v -> Maybe Bool

Expected behavior This line preserves the word instance:

  type instance Key v = Int

Environment

• OS name + version: Mac OS X Sonoma
• Version of the code: 0.7.1.0

[amesgen]

You write

class IsBoolMap v where
  type Key v
  type Key v = Int  -- Invalid syntax

AFAICT, both variants (with and without instance) are valid (they both parse and compile just fine). From the GHC User's Guide:

• The instance keyword is optional.

Are you observing something different?

[lykahb]

I had an unrelated warning on that line and compiled with -Werror. At a glance the disappearing keyword looked like the source of it.