#11796: Warn about unwanted instances in a modular way -------------------------------------+------------------------------------- Reporter: Lemming | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Lemming): It could resolve the long discussion on libraries mailing list about whether we want instances like Foldable (,) or not. With this warning we could both have the instances for those who prefer to use pairs for everything, but do not harm those who consider `length (2,3)` an error. See https://mail.haskell.org/pipermail/libraries/2016-February/026678.html . Conflicting "warn-instance" strings might be resolved with package qualification as I have mentioned in the last paragraph of the proposal. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11796#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler