exceptional xmonad layout instances are rare

exceptions.hs

module Main where

import System.Process
import Data.Char

import Text.PrettyPrint

listModules :: String -> IO [String]
listModules pkgName = 
    -- remove empty lines (possible?) or the exposed-modules: heading
    filter (\x -> not (null x) && isUpper (head x)) . words
    <$> readProcess "ghc-pkg" [  "field", pkgName, "exposed-modules"] ""


mkMod :: [String] -- ^ module names
  -> Doc
mkMod ms = text "{-# LANGUAGE TemplateHaskell #-}\nmodule Main where"
    $$ vcat [ text "import qualified" <+> text m | m <- "XMonad":"IPPrint":"Language.Haskell.TH as TH":ms ]
    $$ hang (text "main = do") 2 (vcat stmts)

 where stmts = [text $ "putStrLn $(TH.reify ''XMonad.LayoutClass" ++
                       ">>= \\ (TH.ClassI _ insts) -> TH.stringE (unlines [ TH.pprint i | i@(TH.InstanceD ctxt _ _) <- insts, not (null ctxt) ]))"]


main = do
    contribs <- listModules "xmonad-contrib"
    writeFile "tmp1.hs" (show (mkMod contribs))
    system "runghc tmp1.hs"


{- these are instances of LayoutClass that have an instance body/constraints
(the part before the =>).

instance (XMonad.Layout.ZoomRow.EQF f_0 a_1,
          GHC.Show.Show a_1,
          GHC.Read.Read a_1,
          GHC.Show.Show (f_0 a_1),
          GHC.Read.Read (f_0 a_1)) => XMonad.Core.LayoutClass (XMonad.Layout.ZoomRow.ZoomRow f_0)
                                                              a_1
instance (XMonad.Core.LayoutClass lt_0 a_1,
          XMonad.Core.LayoutClass lf_2
                                  a_1) => XMonad.Core.LayoutClass (XMonad.Layout.ToggleLayouts.ToggleLayouts lt_0
                                                                                                             lf_2)
                                                                  a_1
instance (XMonad.Core.LayoutClass l1_0 a_1,
          XMonad.Core.LayoutClass l2_2 a_1,
          GHC.Show.Show a_1) => XMonad.Core.LayoutClass (XMonad.Layout.PerWorkspace.PerWorkspace l1_0
                                                                                                 l2_2)
                                                        a_1
instance (XMonad.Core.LayoutClass l1_0 a_1,
          XMonad.Core.LayoutClass l2_2 a_1,
          GHC.Show.Show a_1) => XMonad.Core.LayoutClass (XMonad.Layout.PerScreen.PerScreen l1_0
                                                                                           l2_2)
                                                        a_1
instance (XMonad.Core.LayoutClass l1_0 a_1,
          XMonad.Core.LayoutClass l2_2 a_1,
          GHC.Show.Show a_1) => XMonad.Core.LayoutClass (XMonad.Layout.OnHost.OnHost l1_0
                                                                                     l2_2)
                                                        a_1
instance (Data.Typeable.Internal.Typeable a_0,
          GHC.Show.Show ts_1,
          XMonad.Layout.MultiToggle.HList ts_1 a_0,
          XMonad.Core.LayoutClass l_2
                                  a_0) => XMonad.Core.LayoutClass (XMonad.Layout.MultiToggle.MultiToggle ts_1
                                                                                                         l_2)
                                                                  a_0
instance (XMonad.Core.Message m_0,
          XMonad.Core.LayoutClass l_1
                                  w_2) => XMonad.Core.LayoutClass (XMonad.Layout.MessageControl.Ignore m_0
                                                                                                       l_1)
                                                                  w_2
instance (XMonad.Layout.LayoutModifier.LayoutModifier m_0 a_1,
          XMonad.Core.LayoutClass l_2
                                  a_1) => XMonad.Core.LayoutClass (XMonad.Layout.LayoutModifier.ModifiedLayout m_0
                                                                                                               l_2)
                                                                  a_1
instance (XMonad.Core.LayoutClass l1_0 a_1,
          XMonad.Core.LayoutClass l2_2
                                  a_1) => XMonad.Core.LayoutClass (XMonad.Layout.LayoutCombinators.NewSelect l1_0
                                                                                                             l2_2)
                                                                  a_1
instance (XMonad.Core.LayoutClass l1_0 w_1,
          XMonad.Core.LayoutClass l2_2 w_1,
          XMonad.Layout.LayoutBuilderP.Predicate p_3 w_1,
          GHC.Show.Show w_1,
          GHC.Read.Read w_1,
          GHC.Classes.Eq w_1,
          Data.Typeable.Internal.Typeable w_1,
          GHC.Show.Show p_3) => XMonad.Core.LayoutClass (XMonad.Layout.LayoutBuilderP.LayoutP p_3
                                                                                              l1_0
                                                                                              l2_2)
                                                        w_1
instance (XMonad.Core.LayoutClass l1_0 a_1,
          XMonad.Core.LayoutClass l2_2 a_1,
          GHC.Read.Read a_1,
          GHC.Show.Show a_1,
          GHC.Classes.Eq a_1,
          Data.Typeable.Internal.Typeable a_1) => XMonad.Core.LayoutClass (XMonad.Layout.LayoutBuilder.LayoutN l1_0
                                                                                                               l2_2)
                                                                          a_1
instance (XMonad.Core.LayoutClass l1_0 a_1,
          XMonad.Core.LayoutClass l2_2
                                  a_1) => XMonad.Core.LayoutClass (XMonad.Layout.IfMax.IfMax l1_0
                                                                                             l2_2)
                                                                  a_1
instance XMonad.Core.LayoutClass l_0
                                 a_1 => XMonad.Core.LayoutClass (XMonad.Layout.Groups.WithID l_0)
                                                                a_1
instance (XMonad.Core.LayoutClass l_0 Graphics.X11.Types.Window,
          XMonad.Core.LayoutClass l2_1
                                  (XMonad.Layout.Groups.Group l_0
                                                              Graphics.X11.Types.Window)) => XMonad.Core.LayoutClass (XMonad.Layout.Groups.Groups l_0
                                                                                                                                                  l2_1)
                                                                                                                     Graphics.X11.Types.Window
instance (XMonad.Core.LayoutClass l_0 (),
          XMonad.Core.LayoutClass l1_1 Graphics.X11.Types.Window,
          XMonad.Core.LayoutClass l2_2
                                  Graphics.X11.Types.Window) => XMonad.Core.LayoutClass (XMonad.Layout.ComboP.CombineTwoP (l_0 ())
                                                                                                                          l1_1
                                                                                                                          l2_2)
                                                                                        Graphics.X11.Types.Window
instance (XMonad.Core.LayoutClass l_0 (),
          XMonad.Core.LayoutClass l1_1 a_2,
          XMonad.Core.LayoutClass l2_3 a_2,
          GHC.Read.Read a_2,
          GHC.Show.Show a_2,
          GHC.Classes.Eq a_2,
          Data.Typeable.Internal.Typeable a_2) => XMonad.Core.LayoutClass (XMonad.Layout.Combo.CombineTwo (l_0 ())
                                                                                                          l1_1
                                                                                                          l2_3)
                                                                          a_2
-}