From 6fff76e304a7aa037d49e098db960630ef0e36ce Mon Sep 17 00:00:00 2001
From: Oleg Grenrus <oleg.grenrus@iki.fi>
Date: Mon, 15 May 2017 19:45:14 +0300
Subject: [PATCH] Add regression test for #734

---
 servant/servant.cabal                   |  1 +
 servant/test/Servant/Utils/EnterSpec.hs | 32 +++++++++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 servant/test/Servant/Utils/EnterSpec.hs

diff --git a/servant/servant.cabal b/servant/servant.cabal
index 64039227..94d22668 100644
--- a/servant/servant.cabal
+++ b/servant/servant.cabal
@@ -112,6 +112,7 @@ test-suite spec
       Servant.API.ContentTypesSpec
       Servant.API.ResponseHeadersSpec
       Servant.Utils.LinksSpec
+      Servant.Utils.EnterSpec
   build-depends:
       base == 4.*
     , base-compat
diff --git a/servant/test/Servant/Utils/EnterSpec.hs b/servant/test/Servant/Utils/EnterSpec.hs
new file mode 100644
index 00000000..0453f83a
--- /dev/null
+++ b/servant/test/Servant/Utils/EnterSpec.hs
@@ -0,0 +1,32 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeOperators #-}
+module Servant.Utils.EnterSpec where
+
+import Test.Hspec (Spec)
+
+import Servant.API
+import Servant.Utils.Enter
+
+-------------------------------------------------------------------------------
+-- https://github.com/haskell-servant/servant/issues/734
+-------------------------------------------------------------------------------
+
+-- This didn't fail if executed in GHCi; cannot have as a doctest.
+
+data App a
+
+f :: App :~> App
+f = NT id
+
+server :: App Int :<|> (String -> App Bool)
+server = undefined
+
+server' :: App Int :<|> (String -> App Bool)
+server' = enter f server
+
+-------------------------------------------------------------------------------
+-- Spec
+-------------------------------------------------------------------------------
+
+spec :: Spec
+spec = return ()