#5462: Deriving clause for arbitrary classes -------------------------------------+------------------------------------- Reporter: simonpj | Owner: dreixel Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: 7.2.1 Component: Compiler | Keywords: Generics Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: #7346 None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by hvr): Replying to [comment:34 simonpj]:

* Make it possible for a library author to make a class `C` which can be used in `..deriving( C )` just like built-in classes. * Ultimately: remove the built-in code for deriving `Eq`, `Ord` etc with generic code.

IMHO the value of theses two goals should not be underestimated, as this feature would allow for custom Prelude to provide (for instance) custom `Eq`/`Ord` instances different from the default ones generated by GHC while allowing to use automatic derivation as if they were built-ins (which I don't think `RebindableSyntax` already allows at this point). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5462#comment:35 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler