[Hackage] #594: Unhelpful error message for "module found in multiple packages"

Hackage trac at galois.com
Tue Sep 29 15:00:36 EDT 2009

#594: Unhelpful error message for "module found in multiple packages"
  Reporter:  guest               |        Owner:         
      Type:  enhancement         |       Status:  new    
  Priority:  normal              |    Milestone:         
 Component:  cabal-install tool  |      Version:
  Severity:  normal              |     Keywords:         
Difficulty:  unknown             |   Ghcversion:         
  Platform:                      |  
 I was checking whether cabal-install would install my "extcore" package,
 and got:
 $ sudo cabal install extcore --enable-library-profiling --reinstall
 Resolving dependencies...
 Configuring extcore-0.3...
 Preprocessing library extcore-0.3...
 Building extcore-0.3...

     Could not find module `Data.Generics':
       it was found in multiple packages: base- syb
 cabal: Error: some packages failed to install:
 extcore-0.3 failed during the building phase. The exception was:
 exit: ExitFailure 1

 This is an unhelpful error message because it gives the user no
 information about what they have to do to continue. Since I'm the package
 author, I was able to figure out that I needed to change the .cabal file
 to depend on base >= 4. In general, the error message should explain that
 this is a bug in the package description and to report it to the package

 cabal-install 0.6.2, library version

Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/594>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects

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