#8165: Use GeneralizedNewtypeDeriving to automatically create associated type families -------------------------------------+------------------------------------- Reporter: MikeIzbicki | Owner: RyanGlScott Type: feature request | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler (Type | Version: 7.6.3 checker) | Resolution: | Keywords: TypeFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #2721 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * owner: goldfire => RyanGlScott Comment: Right, I didn't say the last type parameter of `T` had to be the newtype. Rather, the last type parameter of the class `C` (`z` in the example in comment:18) just has to occur somewhere in the type parameters of `T`.
I'm far from sure if this is really worth the effort of explaining and implementing it.
I disagree! Really, this is a quite straightforward idea (with a couple of small gotchas, like the one you observed), and I've implemented most of it already—I just need to polish up the documentation, update the GHC wiki, and post a Phabricator Diff. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8165#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler