#12616: type synonyms confuse generalized newtype deriving role checking -------------------------------------+------------------------------------- Reporter: daviddarais | Owner: goldfire Type: bug | Status: merge Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: generalized | newtype deriving roles rankntypes Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | deriving/should_compile/T12616 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * status: new => merge * testcase: => deriving/should_compile/T12616 Comment: Great bug report thank you. Although the patch looks large it isn't really. But it ''does'' change the behaviour of GHC with `-XImpredicativeTypes`. Since we don't advertise any particular behaviour, that might seem OK. Or someone might complain. Still, I'm inclined to merge the change to the 8.0 branch because it makes the compiler more stable and predictable. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12616#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler