[GHC] #1942: Warnings even with -w specified

[GHC]

#1942: Warnings even with -w specified
--------------------------+-------------------------------------------------
 Reporter:  NeilMitchell  |          Owner:         
     Type:  bug           |         Status:  new    
 Priority:  normal        |      Milestone:         
Component:  Compiler      |        Version:  6.8.1  
 Severity:  normal        |       Keywords:         
 Testcase:                |   Architecture:  Unknown
       Os:  Windows       |  
--------------------------+-------------------------------------------------
 Sorry for the long test case, but my attempt at reducing it caused the bug
 to disappear!

 {{{
 C:\Documents\Uni>darcs get http://www.cs.york.ac.uk/fp/darcs/derive
 Directory 'C:/Documents/Uni/derive' already exists, creating repository as
 'C:/D
 ocuments/Uni/derive_0'
 Copying patch 349 of 349... done!
 Applying patch 349 of 349... done.
 Finished getting.

 C:\Documents\Uni>cd derive_0

 C:\Documents\Uni\derive_0>runhaskell Setup configure
 Configuring derive-0.1...

 C:\Documents\Uni\derive_0>runhaskell Setup build
 Preprocessing library derive-0.1...
 Preprocessing executables for derive-0.1...
 Building derive-0.1...
 [ 1 of 40] Compiling Language.Haskell.TH.SYB ( Language/Haskell/TH/SYB.hs,
 dist\
 build/Language/Haskell/TH/SYB.o )
 [ 2 of 40] Compiling Language.Haskell.TH.FixedPpr (
 Language/Haskell/TH/FixedPpr
 .hs, dist\build/Language/Haskell/TH/FixedPpr.o )
 [ 3 of 40] Compiling Language.Haskell.TH.Data (
 Language/Haskell/TH/Data.hs, dis
 t\build/Language/Haskell/TH/Data.o )
 [ 4 of 40] Compiling Language.Haskell.TH.Helper (
 Language/Haskell/TH/Helper.hs,
  dist\build/Language/Haskell/TH/Helper.o )
 [ 5 of 40] Compiling Language.Haskell.TH.Peephole (
 Language/Haskell/TH/Peephole
 .hs, dist\build/Language/Haskell/TH/Peephole.o )
 [ 6 of 40] Compiling Language.Haskell.TH.All ( Language/Haskell/TH/All.hs,
 dist\
 build/Language/Haskell/TH/All.o )

 Language/Haskell/TH/All.hs:8:4:
     Warning: The export item `module Language.Haskell.TH.SYB' exports
 nothing
 [ 7 of 40] Compiling Data.Derive.Uniplate ( Data/Derive/Uniplate.hs,
 dist\build/
 Data/Derive/Uniplate.o )
 [ 8 of 40] Compiling Data.Derive.Typeable ( Data/Derive/Typeable.hs,
 dist\build/
 Data/Derive/Typeable.o )
 [ 9 of 40] Compiling Data.Derive.TTypeable ( Data/Derive/TTypeable.hs,
 dist\buil
 d/Data/Derive/TTypeable.o )
 [10 of 40] Compiling Data.Derive.Show ( Data/Derive/Show.hs,
 dist\build/Data/Der
 ive/Show.o )
 [11 of 40] Compiling Data.Derive.Set  ( Data/Derive/Set.hs,
 dist\build/Data/Deri
 ve/Set.o )
 [12 of 40] Compiling Data.Derive.Serial ( Data/Derive/Serial.hs,
 dist\build/Data
 /Derive/Serial.o )

 C:\Documents\Uni\derive_0>head Language\Haskell\TH\All.hs
 {-# OPTIONS_GHC -w #-}

 module Language.Haskell.TH.All (
     module Language.Haskell.TH.All,
     module Language.Haskell.TH.Syntax, module
 Language.Haskell.TH.Peephole,
     module Language.Haskell.TH.Helper, module
 Language.Haskell.TH.FixedPpr,
     module Language.Haskell.TH.Data,
     module Language.Haskell.TH.SYB
     ) where
 }}}

 i.e. using the Derive darcs version, there is a warning being raised for
 Language.Haskell.TH.All even though -w is being specified. In the module
 Language.Haskell.TH.SYB (which is indeed empty after CPP'ing) an identical
 error is raised, which can be removed with -fno-warn-unused-imports.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1942>
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