[Hackage] #831: Strange message

Hackage cvs-ghc at haskell.org
Mon Apr 18 13:44:42 CEST 2011

#831: Strange message
  Reporter:  Ptharien's Flame    |        Owner:                                        
      Type:  defect              |       Status:  new                                   
  Priority:  normal              |    Milestone:                                        
 Component:  cabal-install tool  |      Version:                              
  Severity:  normal              |     Keywords:  base, cabal, install, ghc, version, no
Difficulty:  unknown             |   Ghcversion:                                        
  Platform:  Mac OS              |  

Comment(by duncan):

 Apparently your `base` package is broken, probably missing dependencies.
 Run `ghc-pkg check`.

 Cabal interprets broken packages as if they did not exist at all, so
 that's why instead of saying that base is broken, it says that it is
 missing. The improvement we could make here would be to add custom reasons
 for constraints, so that when constraints cannot be met, the associated
 reasons are given. Technically here we have a constraint conflict between
 the constraint 'must use an installed instance of base' and 'do not use
 base version-x.y'. What we need to do is attach a reason 'because it is
 broken' to the latter constraint. Then we could improve the error message.
 We should also say why we need base, which will be because `ObjectIO` (and
 everything else) depends on it.

Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/831#comment:1>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects

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