never executed always true always false

    1 {-# LANGUAGE DeriveGeneric #-}
    2 module Distribution.Client.Dependency.Types (
    3     PreSolver(..),
    4     Solver(..),
    5     PackagesPreferenceDefault(..),
    6   ) where
    7 
    8 import Distribution.Client.Compat.Prelude
    9 import Prelude ()
   10 
   11 import Text.PrettyPrint (text)
   12 
   13 import qualified Distribution.Compat.CharParsing as P
   14 
   15 
   16 -- | All the solvers that can be selected.
   17 data PreSolver = AlwaysModular
   18   deriving (Eq, Ord, Show, Bounded, Enum, Generic)
   19 
   20 -- | All the solvers that can be used.
   21 data Solver = Modular
   22   deriving (Eq, Ord, Show, Bounded, Enum, Generic)
   23 
   24 instance Binary PreSolver
   25 instance Binary Solver
   26 
   27 instance Structured PreSolver
   28 instance Structured Solver
   29 
   30 instance Pretty PreSolver where
   31     pretty AlwaysModular = text "modular"
   32 
   33 instance Parsec PreSolver where
   34     parsec = do
   35         name <- P.munch1 isAlpha
   36         case map toLower name of
   37             "modular" -> return AlwaysModular
   38             _         -> P.unexpected $ "PreSolver: " ++ name
   39 
   40 -- | Global policy for all packages to say if we prefer package versions that
   41 -- are already installed locally or if we just prefer the latest available.
   42 --
   43 data PackagesPreferenceDefault =
   44 
   45      -- | Always prefer the latest version irrespective of any existing
   46      -- installed version.
   47      --
   48      -- * This is the standard policy for upgrade.
   49      --
   50      PreferAllLatest
   51 
   52      -- | Always prefer the installed versions over ones that would need to be
   53      -- installed. Secondarily, prefer latest versions (eg the latest installed
   54      -- version or if there are none then the latest source version).
   55    | PreferAllInstalled
   56 
   57      -- | Prefer the latest version for packages that are explicitly requested
   58      -- but prefers the installed version for any other packages.
   59      --
   60      -- * This is the standard policy for install.
   61      --
   62    | PreferLatestForSelected
   63   deriving Show