Perhaps such warnings could be added to a tool like HLint? I do not think they belong in GHC. On Thu, Feb 25, 2016 at 5:40 AM, Augustsson, Lennart < Lennart.Augustsson@sc.com> wrote:
Yes, at this point I think the best we can do is to make sure we get good warnings. I'd suggest that we can attach a warning to a method in each instance. So when using length on a tuple we'd get a warning. I don't even want to upgrade ghc to get the FTP until such a warning is in place (we are still on 7.8).
-----Original Message----- From: Libraries [mailto:libraries-bounces@haskell.org] On Behalf Of Phil Ruffwind Sent: 25 February 2016 13:01 To: Manuel Gómez Cc: Haskell Libraries Subject: Re: Haskell Foldable Wats
2. to implement a language extension in GHC that allows source language to specify a certain instance will never be defined and a type error shall be thrown statically at any use site, or
How about a feature that allows GHC to warn whenever a certain instance is used? That way, if you don't like a certain instance, you can put {-# FORBIDINSTANCE Foldable ((,) a) #-} in your modules and get warnings whenever that instance is used. _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
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