#10831: DeriveFunctor not capable of deriving when wrapping Either -------------------------------------+------------------------------------- Reporter: htebalaka | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: MacOS X Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- GHC can derive Functor for Okay, but rejects the equivalent Bad. {{{#!hs {-# LANGUAGE DeriveFunctor #-} data Okay f g a b = Inl (f a b) | Inr (g a b) deriving (Functor) newtype Bad f g a b = Bad (Either (f a b) (g a b)) deriving (Functor) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10831 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler