#8813: further support deriving instances Typeable1, Typeable2, etc ----------------------------------------------+---------------------------- Reporter: maeder | Owner: Type: task | Status: closed Priority: normal | Milestone: Component: Compiler | Version: Resolution: wontfix | 7.8.1-rc1 Operating System: Unknown/Multiple | Keywords: Type of failure: GHC rejects valid program | Architecture: Test Case: | Unknown/Multiple Blocking: | Difficulty: Unknown | Blocked By: | Related Tickets: ----------------------------------------------+---------------------------- Comment (by dreixel): Replying to [comment:4 maeder]:
What is the problem to add (renamed) copies of Typeable (named TypeableN) and add generic instances "TypeableN k => Typeable k" and re- export those via Data.Typeable? This would allow to test unmodified existing code!!!
(These intermediate TypeableN classes may be marked to be deprecated later)
I thought about ways to do this before, and never came to a reasonable solution. If you can find one, please let us know. For example, instances like `Typeable1 t => Typeable t` are impossible, as all `t`s match this instance head. I also didn't see how to reconcile the type of the old `typeOF` with the new poly-kinded `typeRep`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8813#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler