[Hackage] #773: Default value for flag ignored, but explicit flag assignment is honored

Hackage cvs-ghc at haskell.org
Fri Dec 3 12:19:18 CET 2010


#773: Default value for flag ignored, but explicit flag assignment is honored
----------------------------+-----------------------------------------------
  Reporter:  guest          |        Owner:         
      Type:  defect         |       Status:  new    
  Priority:  normal         |    Milestone:         
 Component:  Cabal library  |      Version:  1.8.0.6
  Severity:  normal         |     Keywords:         
Difficulty:  unknown        |   Ghcversion:         
  Platform:                 |  
----------------------------+-----------------------------------------------

Comment(by malcolm.wallace@…):

 This is not a bug, it is a design feature.  The "default" value of a flag
 is only a hint to the constraint solver that it should try using that flag
 value first, before trying other values.  If the constraint solver was
 unable to find a valid solution to the dependencies using your default
 value of "True", then it continues looking with the value "False", and
 then apparently does find a valid solution respecting all dependencies
 listed there.

 However, if you specify a flag value on the command-line, the constraint
 solver will not try using other values for flags: it trusts that the user
 really wants what they explicitly asked for.  In your case, I think if you
 specify True for the value of the flag on the commandline, the solver will
 probably fail to find a solution, and tell you why.

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/773#comment:1>
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