#12860: GeneralizedNewtypeDeriving + MultiParamTypeClasses sends typechecker into an infinite loop -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Keywords: FunDeps, Resolution: | deriving Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Maybe you want dis-aggregate `checkValidInstance`. * I think you need `checkInstTermination` on every iteration. Probably even if `UndecidableInstances` is on; I'm not sure that automatic deriving should ever generate a non-provably-terminating instance. * Then you can call `checkValidInstance` itself right at the end -- that will check the coverage conditions. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12860#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler