#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 maeder): The other simple alternative is to patch the renamer and rename the class Data.Typeable.TypeableN to Data.Typeable.Typeable. This surely does not reconcile typeOF and typeRep, but hand-written instances have been (sort of) deprecated long before. I'm not familiar with the internals of Data.Typeable but the following is not impossible: {{{ {-# Language FlexibleInstances, UndecidableInstances #-} class Pretty a where pretty :: a -> String instance Show a => Pretty a where pretty = show }}} Furthermore, Data.!OldTypeable should be removed. It's more harmful to provide a second incompatible Typeable class. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8813#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler