#15310: Derive Generic1 instances for types of kind (k -> *) -> * that include applications of the parameter -------------------------------------+------------------------------------- Reporter: cedricshock | Owner: (none) Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: checker) | Keywords: DeriveGeneric Resolution: | Generic1 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 cedricshock): I wrote an implementation of `Generic1` deriving using `ParAp0` and `ParAp1`. You can preview it in this PR: https://github.com/Cedev/ghc/pull/1 I could use some practical advice and help on what to do next 1. I don't have a test case for a kind `(k -> *) -> *` where `k` isn't `*`. If you have any ideas, especially for a test case where `k ~ Constraint`, I'd appreciate them. 2. There are types in `base` that can now have `Generic1` instances derived for them, starting with `ParAp0` and `ParAp1` themselves. How do I add `Generic1` instances to base without breaking the compiler building, since an old compiler won't be able to derive those `Generic1` instances? 3. What other typeclasses should `ParAp0` and `ParAp1` have instances for? 4. What do I do next? Get feedback from both `ghc-devs` and `glasgow- haskell-users`? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15310#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler