#9821: DeriveAnyClass support for higher-kinded classes + some more comments -------------------------------------+------------------------------------- Reporter: dreixel | Owner: dreixel Type: bug | Status: infoneeded Priority: normal | Milestone: Component: Compiler | Version: 7.9 Resolution: | Keywords: Generics Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #5462, #9968, | Differential Rev(s): #12144 | Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * related: #5462, #9968 => #5462, #9968, #12144 Comment: To the best of my knowledge, here's a summary of the current state of each of those comments: 1. https://phabricator.haskell.org/D476?id=1443#inline-3652 - The logic of this check is explained more thoroughly in [http://git.haskell.org/ghc.git/blob/498ed2664219f7e8f1077f46ad2061aba2f57de4... Note (Determining whether newtype-deriving is appropriate)], which will be further clarified with Phab:D2280. 2. https://phabricator.haskell.org/D476?id=1443#inline-3648 and https://phabricator.haskell.org/D476?id=1443#inline-3646 ask to clarify that `DeriveAnyClass` does indeed only work on argument types of kind `*` and `* -> *` at the moment. #9968 fixed these. So the only thing that remains is to implement support for deriving types of other kinds with `DeriveAnyClass`. I believe that #12144 is very relevant here, since I don't see a way to properly fix that ticket without overhauling the way `DeriveAnyClass` infers its instance contexts in `deriving` clauses. Simon's comment [https://mail.haskell.org/pipermail /ghc-devs/2016-June/012276.html here] provides one suggestion on how to do this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9821#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler