#8631: Need ImpredicativeTypes for GeneralizedNewtypeDeriving? -------------------------------------+------------------------------------ Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by goldfire): I have an implementation plan: * Augment `InstBindings` with a new field `ib_extensions`, which will be a list of `ExtensionFlag`. * In `tcInstanceMethods`, apply these flags using `setXOptM`. * In the `is_newtype` branch of `genInst`, set `ib_extensions` to `[Opt_ImpredicativeTypes]`. * Elsewhere, set `ib_extensions` to `[]`. Seems quite straightforward once I've examined all the plumbing. Expect a patch in the next few hours. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8631#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler