RE: ghc warnings messed up in 6.01
Done, I believe. It'll be in the next release (6.3/6.4). Simon | -Original Message- | From: [EMAIL PROTECTED] [mailto:glasgow-haskell-users- | [EMAIL PROTECTED] On Behalf Of Mike Gunter | Sent: 07 December 2003 16:50 | To: [EMAIL PROTECTED] | 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. - [EMAIL PROTECTED] | --- | ___ | Glasgow-haskell-users mailing list | [EMAIL PROTECTED] | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users | ___ | Glasgow-haskell-users mailing list | [EMAIL PROTECTED] | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
ghc warnings messed up in 6.01
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. - [EMAIL PROTECTED] --- ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: ghc warnings messed up in 6.01
John Meacham wrote: [...] ;ghc -W -fglasgow-exts Foo.hs The current HEAD version (no idea about the release branch) of ghc correctly says: Foo.hs:1: Warning: Module `List' is imported, but nothing from it is used (except perhaps instances visible in `List') Foo.hs:7: Warning: Defined but not used: ds [...] 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. [...] This is your personal opinion and actually a matter of taste: I prefer the new transitive way of issuing the warnings, otherwise you only get a single warning about ds being unused, remove it, recompile, get the next warning, etc. etc. With the new way you can simply remove everything which appears in the unused foo warnings and you're done. Cheers, S. ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
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. - [EMAIL PROTECTED] --- ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
