Merge pull request #388 from bgamari/master

Compatibility with GHC 8.0

Author: kosmikus

servant-server/servant-server.cabal

@@ -66,7 +66,7 @@ library
       , system-filepath    >= 0.4  && < 0.5
       , filepath           >= 1
       , text               >= 1.2  && < 1.3
-      , transformers       >= 0.3  && < 0.5
+      , transformers       >= 0.3  && < 0.6
       , transformers-compat>= 0.4
       , wai                >= 3.0  && < 3.3
       , wai-app-static     >= 3.0  && < 3.2

servant/src/Servant/API/ContentTypes.hs

@@ -169,7 +169,7 @@ class (AllMime list) => AllCTRender (list :: [*]) a where
     handleAcceptH :: Proxy list -> AcceptHeader -> a -> Maybe (ByteString, ByteString)
 
 instance OVERLAPPABLE_
-         (AllMimeRender (ct ': cts) a) => AllCTRender (ct ': cts) a where
+         (Accept ct, AllMime cts, AllMimeRender (ct ': cts) a) => AllCTRender (ct ': cts) a where
     handleAcceptH _ (AcceptHeader accept) val = M.mapAcceptMedia lkup accept
       where pctyps = Proxy :: Proxy (ct ': cts)
             amrs = allMimeRender pctyps val