#8978: Type synonyms in class associated types behave strangely ----------------------------------------------+---------------------------- Reporter: joelteon | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.1 Resolution: | 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 simonpj): Ugh. This is my fault; an egregious blunder in a (cool) clean-up of the type flattener. It's easy to fix (patch coming) but the bug is in the released 7.8.1. Will fix in 7.8.2. It just shows, you never have enough regression tests! It affects any type synonym whose RHS mentions a type family. (Data families are fine.) Such as `Syn` above, or `H` in #8979. Richard's workaround is good; use a type family instead. Sorry about this. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8978#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler