[Hackage] #471: check for ambigious module names

[Hackage]

#471: check for ambigious module names
---------------------------------+------------------------------------------
  Reporter:  duncan              |        Owner:         
      Type:  defect              |       Status:  new    
  Priority:  normal              |    Milestone:         
 Component:  cabal-install tool  |      Version:  1.6.0.1
  Severity:  normal              |     Keywords:         
Difficulty:  unknown             |   Ghcversion:         
  Platform:                      |  
---------------------------------+------------------------------------------
 Consider an example:

 {{{
 build-depends:
   base, extensible-exceptions
 }}}

 The package `base-4.0.0.0` and `extensible-exceptions-0.1.1.0` both
 provide the module `Control.Exception`. This means it is impossible to
 pick both packages as direct dependencies of any single package.

 We should check for this situation at configure time and/or in cabal-
 install when planning an installation plan.

 Actually trying to avoid this situation may be rather tricky and it is not
 expected to occur often. So a simple check may be sufficient. If it starts
 to occur often in practice then we could consider trying to get the
 constraint solver to avoid the situation (perhaps by adding it to the
 checks for if a package is installable at all, see #420).

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/471>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects