From b624393ea5d75a7ef87b2abb6508035d9f2f3eef Mon Sep 17 00:00:00 2001
From: Joshua Potter <jrpotter2112@gmail.com>
Date: Sat, 13 Jan 2018 23:55:47 -0800
Subject: [PATCH] Add undefined definition.

---
 postlude.cabal  |  1 +
 src/Postlude.hs | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/postlude.cabal b/postlude.cabal
index c78cf54..4b5405d 100644
--- a/postlude.cabal
+++ b/postlude.cabal
@@ -21,6 +21,7 @@ library
                        bytestring == 0.10.8.1,
                        exceptions == 0.8.3,
                        free == 4.12.4,
+                       ghc-prim == 0.5.0.0,
                        mtl == 2.2.1,
                        text == 1.2.2.2,
                        transformers == 0.5.5.0
diff --git a/src/Postlude.hs b/src/Postlude.hs
index cd2c376..fa69e93 100644
--- a/src/Postlude.hs
+++ b/src/Postlude.hs
@@ -1,4 +1,6 @@
 {-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE TypeInType #-}
 
 -- The following maps all imports into a single module alias for easy exporting.
 -- In all cases, we choose to explicitly list all exports (and avoid the use of
@@ -304,3 +306,11 @@ import System.IO as X
 import Text.Read as X
   ( read
   )
+
+import qualified GHC.Err as Err
+import qualified GHC.Stack.Types as Stack.Types
+import qualified GHC.Types as GHC.Types
+
+undefined :: forall (r :: GHC.Types.RuntimeRep). forall (a :: GHC.Types.TYPE r).
+             Stack.Types.HasCallStack => a
+undefined = Err.error "Postlude.undefined"