The fix is merged on the 7.8.2 branch, so you can build it and try. I don't know if anyone has a pre-built binary distribution for your platform
#8978: Type synonyms in class associated types behave strangely ----------------------------------------------+---------------------------- Reporter: joelteon | Owner: Type: bug | Status: closed Priority: highest | Milestone: 7.8.2 Component: Compiler | Version: 7.8.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects valid program | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: ----------------------------------------------+---------------------------- Comment (by Lemming): Replying to [comment:17 simonpj]: though. I can confirm that the problems are gone with the ghc-7.8.1.20140410 built by Michael Snoyman. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8978#comment:18 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler