Hi Richard, No "Split" is a class and is defined here: http://hackage.haskell.org/package/effect-monad-0.6.1/docs/Control-Effect-State.html#t:Split "Union" is a type function (synonym that refers to a type function call): http://hackage.haskell.org/package/effect-monad-0.6.1/docs/Control-Effect-Writer.html#t:Union
thank you for your quick reply! Best, Jan 2015-11-18 17:05 GMT+00:00 Richard Eisenberg <e...@cis.upenn.edu>: > I took just a quick look at this. Is Split a type family? The NthCo > coercion form takes apart a composite equality into its pieces. For > example, if we know (Maybe a ~ Maybe b), then NthCo:0 will tell us that (a > ~ b). In your case, it looks like GHC is trying to deduce (Union '["thres" > :-> Int] []) ~ (Union '["thres" :-> Int] (Unit Reader)) from an equality of > two (Split ...) types. If Split is a type family, this deduction is > unsound. That may be what Core Lint is worried about. > > I'm not surprised that the executable would run with an error. But it > might not in the future. If -dcore-lint fails, it means that there is a > potential type safety issue in the Core code, and this should be taken > seriously. > > I hope this helps! > Richard > > On Nov 18, 2015, at 11:35 AM, Jan Bracker <jan.brac...@googlemail.com> > wrote: > > Hi, > > I am using the type checker plugin interface and I am trying to produce > some evidence for type class instances. During compilation of one of my > examples I get this core-lint error: > > *** Core Lint errors : in result of Simplifier *** > <no location info>: Warning: > [RHS of ds_a6bY :: (Set '["thres" :-> Int], Set (Unit Reader))] > Bad getNth: > Nth:0 > (Nth:2 > (Sub (Sym (TFCo:R:Inv[]Readerfg[0] <'["thres" :-> Int]>_N > <'[]>_N)) > ; (Inv > <Reader>_N <'["thres" :-> Int]>_N (Sym > TFCo:R:Unit[]Reader[0]))_R > ; Sub > (TFCo:R:Inv[]Readerfg[0] <'["thres" :-> Int]>_N <Unit > Reader>_N))) > Split '["thres" :-> Int] '[] (Union '["thres" :-> Int] '[]) > Split > '["thres" :-> Int] > (Unit Reader) > (Union '["thres" :-> Int] (Unit Reader)) > > I suppose "getNth" refers to the constructor "EvTupleSel" from "EvTerm", > "TcNthCo" from "TcCoercion" or to "NthCo" from "Coercion". But I never > produce evidence of the shape "getNth". My evidence production code can be > found at [1] and the only place where evidence of this shape can come > from is my "evaluateType" function [2] that calls "normaliseType" from the > GHC module "FamInstEnv". You can reproduce the error by checking out > commit 144525886ec107af6f1283b26b19f8125c980aa4 from [3] and running "make > effect-example" in the top directory of the repository (GHC 7.10 or better > is required and a sandbox is automatically created). > > The core-lint error does not seem to have any negative consequences when > ignored. The produced executable works fine. Can somebody explain why it > appears and maybe how I can fix it? > > Thank you! > Jan > > [1] > https://github.com/jbracker/polymonad-plugin/blob/144525886ec107af6f1283b26b19f8125c980aa4/src/Control/Polymonad/Plugin/Evidence.hs#L177 > [2] > https://github.com/jbracker/polymonad-plugin/blob/144525886ec107af6f1283b26b19f8125c980aa4/src/Control/Polymonad/Plugin/Evaluate.hs#L29 > [3] https://github.com/jbracker/polymonad-plugin > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > > >
_______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs