Re: un-used record wildcards

Hi Simon, I've seen this issue with GHC 6.12.3 (and assumed it was by design). It occurs with a slight modification of your example: {-# LANGUAGE RecordWildCards #-} module Test where data T = MkT { f,g :: Int } p x = let MkT{..} = x in f This example warns about "Defined but not used: `g'" on the line defining p. I've raised a GHC bug: http://hackage.haskell.org/trac/ghc/ticket/4411 about this warning. Thanks, Neil

Which version of GHC are you using?  GHC 6.12 does not complain about unused variables bound by "..".  Try this, which complains about y, but not g.

Simon

{-# LANGUAGE RecordWildCards #-} module Test where

data T = MkT { f,g :: Int }

p (MkT { .. }) y = f

|  -----Original Message----- |  From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users- |  bounces@haskell.org] On Behalf Of Serge D. Mechveliani |  Sent: 14 October 2010 11:01 |  To: Antoine Latter |  Cc: glasgow-haskell-users@haskell.org |  Subject: Re: un-used record wildcards | |  On Wed, Oct 13, 2010 at 01:47:11PM -0500, Antoine Latter wrote: |  > On Wed, Oct 13, 2010 at 1:02 PM, Serge D. Mechveliani |  wrote: |  > > Dear GHC developers, |  > > |  > > I use the language extension of RecordWildcards, for example, |  > >                                f (Foo {foo1 = n, foo2 = m, ..}) = ... |  > > |  > > But the complier warns about un-used values of  foo3, foo4, |  > > probably, due to the extension of |  > >                     Foo {foo1 = n, foo2 = m, foo3 = foo3, foo4 = foo4}. |  > > |  > > In such cases, these warnings look as unneeded. |  > > Is it possible to have an un-used binding warnings with exception for |  > > wildcards in records? |  > > If not, then has it sense to introduce an option? |  > > |  > |  > If you're not using foo3 and foo4, can you not put it the ellipsis? |  > that won't cover every case (such as where you're using foo3 but not |  > foo4). |  > |  > Antoine |  > | |  Indeed, thank you. |  It occurs that under RecordWildcards the compiler allows to skip some |  record fields in a pattern. |  _______________________________________________ |  Glasgow-haskell-users mailing list |  Glasgow-haskell-users@haskell.org |  http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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