Hide "internal" instances

This fixes #37 (http://trac.haskell.org/haddock/ticket/37)

Precisely, we show an instance iff its class and all the types are exported by
non-hidden modules.

2 files changed, 55 insertions, 7 deletions

diff --git a/src/Haddock/Interface.hs b/src/Haddock/Interface.hs
index 09f01883..0003cba2 100644
--- a/src/Haddock/Interface.hs
+++ b/src/Haddock/Interface.hs
@@ -43,6 +43,7 @@ import Haddock.Utils
 import Control.Monad
 import Data.List
 import qualified Data.Map as Map
+import qualified Data.Set as Set
 import Distribution.Verbosity
 import System.Directory
 import System.FilePath
@@ -71,8 +72,12 @@ processModules verbosity modules flags extIfaces = do
                                    , iface <- ifInstalledIfaces ext ]
   interfaces <- createIfaces0 verbosity modules flags instIfaceMap
 
+  let exportedNames =
+        Set.unions $ map (Set.fromList . ifaceExports) $
+        filter (\i -> not $ OptHide `elem` ifaceOptions i) interfaces
+      mods = Set.fromList $ map ifaceMod interfaces
   out verbosity verbose "Attaching instances..."
-  interfaces' <- attachInstances interfaces instIfaceMap
+  interfaces' <- attachInstances (exportedNames, mods) interfaces instIfaceMap
 
   out verbosity verbose "Building cross-linking environment..."
   -- Combine the link envs of the external packages into one
diff --git a/src/Haddock/Interface/AttachInstances.hs b/src/Haddock/Interface/AttachInstances.hs
index c012f2e0..089f31b4 100644
--- a/src/Haddock/Interface/AttachInstances.hs
+++ b/src/Haddock/Interface/AttachInstances.hs
@@ -20,6 +20,7 @@ import Haddock.Convert
 import Control.Arrow
 import Data.List
 import qualified Data.Map as Map
+import qualified Data.Set as Set
 
 import GHC
 import Name
@@ -36,21 +37,24 @@ import PrelNames
 import FastString
 #define FSLIT(x) (mkFastString# (x#))
 
+type ExportedNames = Set.Set Name
+type Modules = Set.Set Module
+type ExportInfo = (ExportedNames, Modules)
 
-attachInstances :: [Interface] -> InstIfaceMap -> Ghc [Interface]
-attachInstances ifaces instIfaceMap = mapM attach ifaces
+attachInstances :: ExportInfo -> [Interface] -> InstIfaceMap -> Ghc [Interface]
+attachInstances expInfo ifaces instIfaceMap = mapM attach ifaces
   where
     -- TODO: take an IfaceMap as input
     ifaceMap = Map.fromList [ (ifaceMod i, i) | i <- ifaces ]
 
     attach iface = do
-      newItems <- mapM (attachToExportItem iface ifaceMap instIfaceMap)
+      newItems <- mapM (attachToExportItem expInfo iface ifaceMap instIfaceMap)
                        (ifaceExportItems iface)
       return $ iface { ifaceExportItems = newItems }
 
 
-attachToExportItem :: Interface -> IfaceMap -> InstIfaceMap -> ExportItem Name -> Ghc (ExportItem Name)
-attachToExportItem iface ifaceMap instIfaceMap export =
+attachToExportItem :: ExportInfo -> Interface -> IfaceMap -> InstIfaceMap -> ExportItem Name -> Ghc (ExportItem Name)
+attachToExportItem expInfo iface ifaceMap instIfaceMap export =
   case export of
     ExportDecl { expItemDecl = L _ (TyClD d) } -> do
       mb_info <- getAllInfo (unLoc (tcdLName d))
@@ -59,7 +63,8 @@ attachToExportItem iface ifaceMap instIfaceMap export =
               expItemInstances =
                 case mb_info of
                   Just (_, _, instances) ->
-                    let insts = map (first synifyInstHead) $ sortImage (first instHead)
+                    let insts = map (first synifyInstHead) $ sortImage (first instHead) $
+                                filter (\((_,_,cls,tys),_) -> not $ isInstanceHidden expInfo cls tys)
                                 [ (instanceHead i, getName i) | i <- instances ]
                     in [ (inst, lookupInstDoc name iface ifaceMap instIfaceMap)
                        | (inst, name) <- insts ]
@@ -140,3 +145,41 @@ funTyConName = mkWiredInName gHC_PRIM
                         funTyConKey
                         (ATyCon funTyCon)       -- Relevant TyCon
                         BuiltInSyntax
+
+--------------------------------------------------------------------------------
+-- Filtering hidden instances
+--------------------------------------------------------------------------------
+
+-- | A class or data type is hidden iff
+--
+-- * it is defined in one of the modules that are being processed
+--
+-- * and it is not exported by any non-hidden module
+isNameHidden :: ExportInfo -> Name -> Bool
+isNameHidden (names, modules) name =
+  nameModule name `Set.member` modules &&
+  not (name `Set.member` names)
+
+-- | We say that an instance is «hidden» iff its class or any (part)
+-- of its type(s) is hidden.
+isInstanceHidden :: ExportInfo -> Class -> [Type] -> Bool
+isInstanceHidden expInfo cls tys =
+    instClassHidden || instTypeHidden
+  where
+    instClassHidden :: Bool
+    instClassHidden = isNameHidden expInfo $ getName cls
+
+    instTypeHidden :: Bool
+    instTypeHidden = any typeHidden tys
+
+    nameHidden :: Name -> Bool
+    nameHidden = isNameHidden expInfo
+
+    typeHidden :: Type -> Bool
+    typeHidden t =
+      case t of
+        TyVarTy {} -> False
+        AppTy t1 t2 -> typeHidden t1 || typeHidden t2
+        TyConApp tcon args -> nameHidden (getName tcon) || any typeHidden args
+        FunTy t1 t2 -> typeHidden t1 || typeHidden t2
+        ForAllTy _ ty -> typeHidden ty