#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 RyanGlScott): I'm afraid that won't work either. `checkInstTermination` only checks the Paterson termination conditions, not the fundep coverage conditions (which are checked separately in `checkInstCoverage`). Indeed, I just tried calling `checkInstTermination` after every iteration of `simplifyDeriv`, but the original program still loops even with that, since `C b a` passes the Paterson termination conditions. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12860#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler