Cleanup up GHC flags in `.cabal` files

  * enable more useful warning flags in `haddock-api`, handle the new
    warnings generated

  * remove `-fwarn-tabs` (now we'd use `-Wtabs`, but this has been in
    `-Wall` for a while now)

3 files changed, 10 insertions, 6 deletions

diff --git a/haddock-api/haddock-api.cabal b/haddock-api/haddock-api.cabal
index 54255e09..4abfd984 100644
--- a/haddock-api/haddock-api.cabal
+++ b/haddock-api/haddock-api.cabal
@@ -63,10 +63,14 @@ library
 
   hs-source-dirs: src
 
-  ghc-options: -funbox-strict-fields -Wall -fwarn-tabs -O2
-  ghc-options: -Wall
-  if impl(ghc >= 8.0)
-    ghc-options: -Wcompat -Wnoncanonical-monad-instances
+  ghc-options: -funbox-strict-fields -O2
+               -Wall
+               -Wcompat
+               -Widentities
+               -Wredundant-constraints
+               -Wnoncanonical-monad-instances
+               -Wmissing-home-modules
+
 
   exposed-modules:
     Documentation.Haddock
diff --git a/haddock-api/src/Haddock/Interface/Specialize.hs b/haddock-api/src/Haddock/Interface/Specialize.hs
index 19b03596..492818bd 100644
--- a/haddock-api/src/Haddock/Interface/Specialize.hs
+++ b/haddock-api/src/Haddock/Interface/Specialize.hs
@@ -295,7 +295,7 @@ renameBinder (KindedTyVar x lname lkind) =
 renameBinder (XTyVarBndr nec) = noExtCon nec
 
 -- | Core renaming logic.
-renameName :: (Eq name, SetName name) => name -> Rename name name
+renameName :: SetName name => name -> Rename name name
 renameName name = do
     RenameEnv { .. } <- get
     case Map.lookup (getName name) rneCtx of
diff --git a/haddock-api/src/Haddock/InterfaceFile.hs b/haddock-api/src/Haddock/InterfaceFile.hs
index 7b0f29f4..cb60fb00 100644
--- a/haddock-api/src/Haddock/InterfaceFile.hs
+++ b/haddock-api/src/Haddock/InterfaceFile.hs
@@ -158,7 +158,7 @@ writeInterfaceFile filename iface = do
 type NameCacheAccessor m = (m NameCache, NameCache -> m ())
 
 
-nameCacheFromGhc :: forall m. (GhcMonad m, MonadIO m) => NameCacheAccessor m
+nameCacheFromGhc :: GhcMonad m => NameCacheAccessor m
 nameCacheFromGhc = ( read_from_session , write_to_session )
   where
     read_from_session = do