#15712: GHC panic with -XDerivingVia -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Resolution: | Keywords: DerivingVia Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Iceland_jack): This is without the https://hackage.haskell.org/package/kan- extensions-5.2/docs/Control-Monad-Codensity.html dependency {{{#!hs {-# Language RankNTypes #-} {-# Language DerivingVia #-} {-# Language DeriveFunctor #-} -- import Control.Monad.Codensity import Data.Kind newtype Codensity f a = Codensity (forall xx. (a -> f xx) -> f xx) deriving Functor newtype GEndo m a = GEndo (m a -> m a) newtype LogicT m a = LogicT (forall xx. (a -> (m xx -> m xx)) -> (m xx -> m xx)) deriving (Functor) via (Codensity GEndo) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15712#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler