Done, I believe. It'll be in the next release (6.3/6.4). Simon | -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users- | bounces@haskell.org] On Behalf Of Mike Gunter | Sent: 07 December 2003 16:50 | To: glasgow-haskell-users@haskell.org | Subject: Re: ghc warnings messed up in 6.01 | | | Simon seems to have agreed that The Right Thing is to treat bindings | with names beginning with an underscore as if they are used w.r.t. to | the bindings they use (they're already treated as used w.r.t. warnings | for themselves.) With this enhancement (and the other warning fixes | apparently already in HEAD), you should be able to change "ds" to | "_ds" and get no warnings. | | BTW (here's the real point of my message :-)), is this enchancement | planned? For when? Thanks. | | mike | | | > has anyone else noticed that the warnings generated by ghc appear to | > have become quite incorrect in many cases? | > | > in particular, the 'defined but not used' warning is generated | > spuriously a lot. almost as if it is being checked after dead code | > elimination and desugaring of some sort.. | > | > here is an example which touches all the reproducable bugs I have found. | > | >> module Main(main) where | >> import List(nub) | >> import Monad() | >> | >> as = repeat 'a' | >> bs = repeat 'b' | >> ds = nub as | >> | >> cs = [(a,b) | a <- as | b <- bs] | >> | >> main = print $ take 10 cs | > | > | > ;ghc -W -fglasgow-exts Foo.hs | > | > Foo.hs:1: | > Warning: Module `List' is imported, but nothing from it is used | > (except perhaps instances visible in `List') | > | > Foo.hs:1: | > Warning: Module `Monad' is imported, but nothing from it is used | > (except perhaps instances visible in `Monad') | > | > Foo.hs:7: Warning: Defined but not used: ds | > | > Foo.hs:9: Warning: Defined but not used: b | > | > Foo.hs:9: Warning: Defined but not used: a | > | > | > notice: | > | > 1) it claims nothing is used by List, when 'nub' definatly is being | > used. (technically true, since ds is not used, but this warning is more | > confusing than anything. my first inclination is to delete the import | > line, causing the program to fail to compile, the only fix seems to be | > to track down the root by hand) | > | > 2) it claims Monad is unused, when I specifically imported it with () | > meaning I don't want any names from it. (i.e., I just want instances) | > | > 3) defined but not used 'ds': yay! the only valid warning. | > | > 4,5) variables bound in parallel list comprehensions always seem to | > generate warnings. | > | > | > AFAIK, none of these were problems in earlier versions of ghc, they are | > quite anoying as they obscure valid warnings. my guess is some | > desugarings and warning passes were accidentally switched around.. | > problem 1 is particularly bad, since a single unused toplevel could | > cascade to generating a ton of warnings, all of which must be sorted | > through to find the actual cause. the others are just anoying as there | > doesn't seem to be a workaround short of disabling warnings. | > | > John | > -- | > ------------------------------------------------------------------------ --- | > John Meacham - California Institute of Technology, Alum. - john@foo.net | > ------------------------------------------------------------------------ --- | > _______________________________________________ | > Glasgow-haskell-users mailing list | > Glasgow-haskell-users@haskell.org | > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users