some GHC 8.0.1 fixes

Language/Haskell/GhcMod/FillSig.hs

@@ -134,7 +134,7 @@ getSignature modSum lineNo colNo = do
             Just (clsName,loc) -> obtainClassInfo minfo clsName loc
             _                  -> return Nothing
 #if __GLASGOW_HASKELL__ >= 800
-      [L loc (G.TyClD (G.FamDecl (G.FamilyDecl info (L _ name) (G.HsQTvs _ vars) _ _)))] -> do
+      [L loc (G.TyClD (G.FamDecl (G.FamilyDecl info (L _ name) (G.HsQTvs _ vars _) _ _)))] -> do
 #elif __GLASGOW_HASKELL__ >= 708
       [L loc (G.TyClD (G.FamDecl (G.FamilyDecl info (L _ name) (G.HsQTvs _ vars) _)))] -> do
 #elif __GLASGOW_HASKELL__ >= 706

Language/Haskell/GhcMod/SrcUtils.hs

@@ -1,4 +1,5 @@
-{-# LANGUAGE TupleSections, FlexibleInstances, Rank2Types, ImpredicativeTypes #-}
+-- TODO: remove CPP once Gap(ed)
+{-# LANGUAGE CPP, TupleSections, FlexibleInstances, Rank2Types, ImpredicativeTypes #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module Language.Haskell.GhcMod.SrcUtils where
@@ -106,7 +107,12 @@ collectSpansTypes withConstraints tcs lc =
         -- list of constraints
         preds = concatMap fst ctys
         -- Type variable substitutions
+#if __GLASGOW_HASKELL__ >= 800
+ -- TODO: move to Gap
+        subs  = G.mkTvSubstPrs $ concatMap snd ctys
+#else
         subs  = G.mkTopTvSubst $ concatMap snd ctys
+#endif
         -- Constrained type
         ty    = G.substTy subs $ G.mkFunTys preds genTyp
       in [(spn, ty)]

NotCPP/Declarations.hs

@@ -133,7 +133,7 @@ boundNames decl =
 #endif
           map ((,) TcClsName) (conNames ctor)
 
-      InstanceD _ _ty _ ->
+      InstanceD {}  -> -- _ _ty _
           error "notcpp: Instance declarations are not supported yet"
       ForeignD _ ->
           error "notcpp: Foreign declarations are not supported yet"