#10598: DeriveAnyClass and GND don't work well together -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by rwbarton): The documentation says "With `-XDeriveAnyClass` you can derive any other class", where "other" seems to allude to the classes which can be derived by GHC extensions as described in sections 7.5.3 and 7.5.4 (we have to ignore section 7.5.5 here since the interaction with GND is described explicitly), as well as, presumably, the classes which can be derived in Haskell 2010. And, in fact, if you try to compile your test case with `-XDeriveAnyClass` only, GHC tells you {{{ Test.hs:2:13: Can't make a derived instance of ‘Functor MyMaybe’: You need DeriveFunctor to derive an instance for this class Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension In the newtype declaration for ‘MyMaybe’ }}} which is consistent with this interpretation (it's the same error you get without `-XDeriveAnyClass`). So, I would expect that in all cases of `deriving (Functor)`, the presence of `-XDeriveAnyClass` should have no effect. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10598#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler