haskell-mueval has been fixed upstream.

  # Patch to consider NIX_GHC just like xmonad does

  dyre = appendPatch super.dyre ./dyre-nix.patch;

  # https://github.com/gwern/mueval/issues/9

  mueval = appendPatch (appendPatch super.mueval ./mueval-fix.patch) ./mueval-nix.patch;

  # Test suite won't compile against tasty-hunit 0.9.x.

  zlib = dontCheck super.zlib;

diff --git a/Mueval/ArgsParse.hs b/Mueval/ArgsParse.hs

index 05c8fd9..0c32e27 100644

--- a/Mueval/ArgsParse.hs

+++ b/Mueval/ArgsParse.hs

@@ -1,10 +1,9 @@

+{-# LANGUAGE CPP #-}

 module Mueval.ArgsParse (Options(..), interpreterOpts, getOptions) where

 import Control.Monad (liftM)

 import System.Console.GetOpt

-import qualified Codec.Binary.UTF8.String as Codec (decodeString)

-

 import Mueval.Context (defaultModules, defaultPackages)

 -- | See the results of --help for information on what each option means.

@@ -98,4 +97,11 @@ header = "Usage: mueval [OPTION...] --expression EXPRESSION..."

 -- | Just give us the end result options; this parsing for

 --   us. Bonus points for handling UTF.

 getOptions :: [String] -> Either (Bool, String) Options

-getOptions = interpreterOpts . map Codec.decodeString

\ No newline at end of file

+getOptions = interpreterOpts . map decodeString

+

+decodeString :: String -> String

+#if __GLASGOW_HASKELL__ >= 702

+decodeString = id

+#else

+decodeString = Codec.decodeString

+#endif

diff --git a/Mueval/Context.hs b/Mueval/Context.hs

index 78925cf..548514c 100644

--- a/Mueval/Context.hs

+++ b/Mueval/Context.hs

@@ -1,3 +1,4 @@

+{-# LANGUAGE CPP #-}

 module Mueval.Context (

   cleanModules,

   defaultModules,

@@ -32,7 +33,9 @@ defaultModules = ["Prelude",

                   "Control.Monad.Error",

                   "Control.Monad.Fix",

                   "Control.Monad.Identity",

+#if !MIN_VERSION_base(4,7,0)

                   "Control.Monad.Instances",

+#endif

                   "Control.Monad.RWS",

                   "Control.Monad.Reader",

                   "Control.Monad.State",

diff --git a/Mueval/Interpreter.hs b/Mueval/Interpreter.hs

index 29b771f..6c39482 100644

--- a/Mueval/Interpreter.hs

+++ b/Mueval/Interpreter.hs

@@ -1,4 +1,5 @@

 {-# LANGUAGE PatternGuards #-}

+{-# LANGUAGE FlexibleContexts #-}

 -- TODO: suggest the convenience functions be put into Hint proper?

 module Mueval.Interpreter where

@@ -12,8 +13,6 @@ import System.Exit (exitFailure)

 import System.FilePath.Posix (takeFileName)

 import qualified Control.Exception.Extensible as E (evaluate,catch,SomeException(..))

-import qualified System.IO.UTF8 as UTF (putStrLn)

-

 import Language.Haskell.Interpreter (eval, set, reset, setImportsQ, loadModules, liftIO,

                                      installedModulesInScope, languageExtensions,

                                      typeOf, setTopLevelModules, runInterpreter, glasgowExtensions,

@@ -100,7 +99,7 @@ mvload lfl = do canonfile <- makeRelativeToCurrentDirectory lfl

 -- flooding. Lambdabot has a similar limit.

 sayIO :: String -> IO ()

 sayIO str = do (out,b) <- render 1024 str

-               UTF.putStrLn out

+               putStrLn out

                when b exitFailure

 -- | Oh no, something has gone wrong. If it's a compilation error pretty print

diff --git a/mueval.cabal b/mueval.cabal

index 3f9406d..b86d796 100644

--- a/mueval.cabal

+++ b/mueval.cabal

@@ -32,7 +32,7 @@ library

         exposed-modules:     Mueval.Parallel, Mueval.Context, Mueval.Interpreter,

                              Mueval.ArgsParse, Mueval.Resources

         build-depends:       base>=4 && < 5, containers, directory, mtl>2, filepath, unix, process,

-                             hint>=0.3.1, show>=0.3, utf8-string, Cabal, extensible-exceptions, simple-reflect

+                             hint>=0.3.1, show>=0.3, Cabal, extensible-exceptions, simple-reflect

         ghc-options:         -Wall -static

 executable mueval-core

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 ->