nixpkgs/pkgs/development/haskell-modules/mueval-nix.patch

diff --git a/Mueval/Interpreter.hs b/Mueval/Interpreter.hs
index 29b771f..6360ee3 100644
--- a/Mueval/Interpreter.hs
+++ b/Mueval/Interpreter.hs
@@ -8,6 +8,7 @@ import Control.Monad.Writer (Any(..),runWriterT,tell)
 import Data.Char (isDigit)
 import Data.List (stripPrefix)
 import System.Directory (copyFile, makeRelativeToCurrentDirectory, removeFile, setCurrentDirectory)
+import System.Environment (lookupEnv)
 import System.Exit (exitFailure)
 import System.FilePath.Posix (takeFileName)
 import qualified Control.Exception.Extensible as E (evaluate,catch,SomeException(..))
@@ -47,6 +48,10 @@ interpreter Options { extensions = exts, namedExtensions = nexts,
                                   -- Explicitly adding ImplicitPrelude because of
                                   -- http://darcsden.com/jcpetruzza/hint/issue/1
                                   unless (null lexts) $ set [languageExtensions := (UnknownExtension "ImplicitPrelude" : lexts)]
+                                  pkgs' <- liftIO $ lookupEnv "NIX_GHC_LIBDIR"
+                                  case pkgs' of
+                                    Just pkgs -> unsafeSetGhcOption ("-package-db " ++ pkgs ++ "/package.conf.d")
+                                    Nothing -> return ()
                                   when trust $ do
                                     unsafeSetGhcOption "-fpackage-trust"
                                     forM_ (trustPkgs >>= words) $ \pkg ->