Add ComprehensiVeAPI test for servant-foreign

servant-foreign/servant-foreign.cabal

@@ -67,6 +67,7 @@ test-suite spec
   other-modules:     Servant.ForeignSpec
   build-depends:     base
                    , hspec >= 2.1.8
+                   , servant
                    , servant-foreign
   default-language:  Haskell2010
   default-extensions:  ConstraintKinds

servant-foreign/test/Servant/ForeignSpec.hs

@@ -6,9 +6,11 @@ module Servant.ForeignSpec where
 import Data.Monoid ((<>))
 import Data.Proxy
 import Servant.Foreign
+import Servant.API.Internal.Test.ComprehensiveAPI
 
 import Test.Hspec
 
+
 spec :: Spec
 spec = describe "Servant.Foreign" $ do
   camelCaseSpec
@@ -22,6 +24,10 @@ camelCaseSpec = describe "camelCase" $ do
     camelCase (FunctionName ["get", "hyphen-ated", "counter"])
       `shouldBe` "getHyphen-atedCounter"
 
+----------------------------------------------------------------------
+
+-- This declaration simply checks that all instances are in place.
+_ = listFromAPI (Proxy :: Proxy LangX) (Proxy :: Proxy String) comprehensiveAPIWithoutRaw
 
 ----------------------------------------------------------------------
 
@@ -30,6 +36,9 @@ data LangX
 instance HasForeignType LangX String NoContent where
   typeFor _ _ _ = "voidX"
 
+instance HasForeignType LangX String (Headers ctyps NoContent) where
+  typeFor _ _ _ = "voidX"
+
 instance HasForeignType LangX String Int where
   typeFor _ _ _ = "intX"