#13065: Prohibit user-defined Generic and Generic1 instances -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature request | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Generics Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * cc: RyanGlScott (added) Comment: I'd like to know what Ryan Scott thinks of this idea. We have some classes (like `Typeable`) where you can't give user instances, but it seems less clear-cut for `Generic`. The efficiency issue is to do with the costs of doing the type-family consistency checks for all the `Generic` instances. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13065#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler