Fix renaming after instance signature specializing (#660)

* rework rename

* Add regression test for Bug 613

* update tests

* update changelog

5 files changed, 418 insertions, 170 deletions

diff --git a/CHANGES.md b/CHANGES.md
index bf60817a..5050339d 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -2,6 +2,8 @@
 
  * to be released
 
+ * Fix renaming of type variables after specializing instance method signatures (#613)
+
  * Move markup related data types to haddock-library
 
 ## Changes in version 2.18.1
diff --git a/haddock-api/src/Haddock/Interface/Specialize.hs b/haddock-api/src/Haddock/Interface/Specialize.hs
index da8c3e7b..84168151 100644
--- a/haddock-api/src/Haddock/Interface/Specialize.hs
+++ b/haddock-api/src/Haddock/Interface/Specialize.hs
@@ -17,7 +17,6 @@ import Name
 import FastString
 
 import Control.Monad
-import Control.Monad.Trans.Reader
 import Control.Monad.Trans.State
 
 import Data.Data
@@ -204,7 +203,7 @@ setInternalOccName occ name =
 
 -- | Compute set of free variables of given type.
 freeVariables :: forall name. (NamedThing name, DataId name)
-              => HsType name -> Set NameRep
+              => HsType name -> Set Name
 freeVariables =
     everythingWithState Set.empty Set.union query
   where
@@ -213,7 +212,7 @@ freeVariables =
             (Set.empty, Set.union ctx (bndrsNames bndrs))
         Just (HsTyVar _ (L _ name))
             | getName name `Set.member` ctx -> (Set.empty, ctx)
-            | otherwise -> (Set.singleton $ getNameRep name, ctx)
+            | otherwise -> (Set.singleton $ getName name, ctx)
         _ -> (Set.empty, ctx)
     bndrsNames = Set.fromList . map (getName . tyVarName . unLoc)
 
@@ -225,33 +224,36 @@ freeVariables =
 -- @(a -> b)@ we get @(a -> b) -> b@ where first occurrence of @b@ refers to
 -- different type variable than latter one. Applying 'rename' function
 -- will fix that type to be visually unambiguous again (making it something
--- like @(a -> c) -> b@).
-rename :: SetName name => Set NameRep -> HsType name -> HsType name
-rename fv typ = runReader (renameType typ) $ RenameEnv
-    { rneFV = fv
-    , rneCtx = Map.empty
-    }
-
+-- like @(a -> b0) -> b@).
+rename :: (Eq name, DataId name, SetName name)
+       => Set Name -> HsType name -> HsType name
+rename fv typ = evalState (renameType typ) env
+  where
+    env = RenameEnv
+      { rneHeadFVs = Map.fromList . map mkPair . Set.toList $ fv
+      , rneSigFVs = Set.map getNameRep $ freeVariables typ
+      , rneCtx = Map.empty
+      }
+    mkPair name = (getNameRep name, name)
 
 -- | Renaming monad.
-type Rename name = Reader (RenameEnv name)
-
--- | Binding generation monad.
-type Rebind name = State (RenameEnv name)
+type Rename name = State (RenameEnv name)
 
 data RenameEnv name = RenameEnv
-    { rneFV :: Set NameRep
-    , rneCtx :: Map Name name
-    }
+  { rneHeadFVs :: Map NameRep Name
+  , rneSigFVs :: Set NameRep
+  , rneCtx :: Map Name name
+  }
 
 
-renameType :: SetName name => HsType name -> Rename name (HsType name)
-renameType (HsForAllTy bndrs lt) = rebind bndrs $ \bndrs' ->
+renameType :: (Eq name, SetName name)
+           => HsType name -> Rename name (HsType name)
+renameType (HsForAllTy bndrs lt) =
     HsForAllTy
-        <$> pure bndrs'
+        <$> mapM (located renameBinder) bndrs
         <*> renameLType lt
 renameType (HsQualTy lctxt lt) =
-  HsQualTy
+    HsQualTy
         <$> located renameContext lctxt
         <*> renameLType lt
 renameType (HsTyVar ip name) = HsTyVar ip <$> located renameName name
@@ -281,85 +283,61 @@ renameType (HsWildCardTy wc) = pure (HsWildCardTy wc)
 renameType (HsAppsTy _) = error "HsAppsTy: Only used before renaming"
 
 
-renameLType :: SetName name => LHsType name -> Rename name (LHsType name)
+renameLType :: (Eq name, SetName name)
+            => LHsType name -> Rename name (LHsType name)
 renameLType = located renameType
 
 
-renameLTypes :: SetName name => [LHsType name] -> Rename name [LHsType name]
+renameLTypes :: (Eq name, SetName name)
+             => [LHsType name] -> Rename name [LHsType name]
 renameLTypes = mapM renameLType
 
 
-renameContext :: SetName name => HsContext name -> Rename name (HsContext name)
+renameContext :: (Eq name, SetName name)
+              => HsContext name -> Rename name (HsContext name)
 renameContext = renameLTypes
 
-{-
-renameLTyOp :: SetName name => LHsTyOp name -> Rename name (LHsTyOp name)
-renameLTyOp (wrap, lname) = (,) wrap <$> located renameName lname
--}
-
-
-renameName :: SetName name => name -> Rename name name
-renameName name = do
-    RenameEnv { rneCtx = ctx } <- ask
-    pure $ fromMaybe name (Map.lookup (getName name) ctx)
-
-
-rebind :: SetName name
-       => [LHsTyVarBndr name] -> ([LHsTyVarBndr name] -> Rename name a)
-       -> Rename name a
-rebind lbndrs action = do
-    (lbndrs', env') <- runState (rebindLTyVarBndrs lbndrs) <$> ask
-    local (const env') (action lbndrs')
-
 
-rebindLTyVarBndrs :: SetName name
-                  => [LHsTyVarBndr name] -> Rebind name [LHsTyVarBndr name]
-rebindLTyVarBndrs lbndrs = mapM (located rebindTyVarBndr) lbndrs
+renameBinder :: (Eq name, SetName name)
+             => HsTyVarBndr name -> Rename name (HsTyVarBndr name)
+renameBinder (UserTyVar lname) = UserTyVar <$> located renameName lname
+renameBinder (KindedTyVar lname lkind) =
+  KindedTyVar <$> located renameName lname <*> located renameType lkind
 
 
-rebindTyVarBndr :: SetName name
-                => HsTyVarBndr name -> Rebind name (HsTyVarBndr name)
-rebindTyVarBndr (UserTyVar (L l name)) =
-    UserTyVar . L l <$> rebindName name
-rebindTyVarBndr (KindedTyVar name kinds) =
-    KindedTyVar <$> located rebindName name <*> pure kinds
-
-
-rebindName :: SetName name => name -> Rebind name name
-rebindName name = do
+-- | Core renaming logic.
+renameName :: (Eq name, SetName name) => name -> Rename name name
+renameName name = do
     RenameEnv { .. } <- get
-    taken <- takenNames
     case Map.lookup (getName name) rneCtx of
-        Just name' -> pure name'
-        Nothing | getNameRep name `Set.member` taken -> freshName name
-        Nothing -> reuseName name
+      Nothing
+        | Just headTv <- Map.lookup (getNameRep name) rneHeadFVs
+        , headTv /= getName name -> freshName name
+      Just name' -> return name'
+      _ -> return name
 
 
 -- | Generate fresh occurrence name, put it into context and return.
-freshName :: SetName name => name -> Rebind name name
+freshName :: SetName name => name -> Rename name name
 freshName name = do
-    env@RenameEnv { .. } <- get
     taken <- takenNames
     let name' = setInternalNameRep (findFreshName taken rep) name
-    put $ env { rneCtx = Map.insert nname name' rneCtx }
+    modify $ \rne -> rne
+      { rneCtx = Map.insert (getName name) name' (rneCtx rne) }
     return name'
   where
     nname = getName name
     rep = getNameRep nname
 
 
-reuseName :: SetName name => name -> Rebind name name
-reuseName name = do
-    env@RenameEnv { .. } <- get
-    put $ env { rneCtx = Map.insert (getName name) name rneCtx }
-    return name
-
-
-takenNames :: NamedThing name => Rebind name (Set NameRep)
+takenNames :: NamedThing name => Rename name (Set NameRep)
 takenNames = do
     RenameEnv { .. } <- get
-    return $ Set.union rneFV (ctxElems rneCtx)
+    return $ headReps rneHeadFVs `Set.union`
+             rneSigFVs `Set.union`
+             ctxElems rneCtx
   where
+    headReps = Set.fromList . Map.keys
     ctxElems = Set.fromList . map getNameRep . Map.elems
 
 
@@ -371,15 +349,7 @@ findFreshName taken =
 
 
 alternativeNames :: NameRep -> [NameRep]
-alternativeNames name
-    | [_] <- nameRepString name = letterNames ++ alternativeNames' name
-  where
-    letterNames = map (stringNameRep . pure) ['a'..'z']
-alternativeNames name = alternativeNames' name
-
-
-alternativeNames' :: NameRep -> [NameRep]
-alternativeNames' name =
+alternativeNames name =
     [ stringNameRep $ str ++ show i | i :: Int <- [0..] ]
   where
     str = nameRepString name
diff --git a/html-test/ref/Bug613.html b/html-test/ref/Bug613.html
new file mode 100644
index 00000000..924f37d4
--- /dev/null
+++ b/html-test/ref/Bug613.html
@@ -0,0 +1,260 @@
+<html xmlns="http://www.w3.org/1999/xhtml"
+><head
+  ><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"
+     /><title
+    >Bug613</title
+    ><link href="#" rel="stylesheet" type="text/css" title="Ocean"
+     /><script src="haddock-util.js" type="text/javascript"
+    ></script
+    ><script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-AMS-MML_HTMLorMML" type="text/javascript"
+    ></script
+    ><script type="text/javascript"
+    >//
+window.onload = function () {pageLoad();};
+//
+</script
+    ></head
+  ><body
+  ><div id="package-header"
+    ><ul class="links" id="page-menu"
+      ><li
+	><a href="#"
+	  >Contents</a
+	  ></li
+	><li
+	><a href="#"
+	  >Index</a
+	  ></li
+	></ul
+      ><p class="caption empty"
+      ></p
+      ></div
+    ><div id="content"
+    ><div id="module-header"
+      ><table class="info"
+	><tr
+	  ><th
+	    >Safe Haskell</th
+	    ><td
+	    >Safe</td
+	    ></tr
+	  ></table
+	><p class="caption"
+	>Bug613</p
+	></div
+      ><div id="synopsis"
+      ><p id="control.syn" class="caption expander" onclick="toggleSection('syn')"
+	>Synopsis</p
+	><ul id="section.syn" class="hide" onclick="toggleSection('syn')"
+	><li class="src short"
+	  ><span class="keyword"
+	    >class</span
+	    > <a href="#"
+	    >Functor</a
+	    > f <span class="keyword"
+	    >where</span
+	    ><ul class="subs"
+	    ></ul
+	    ></li
+	  ><li class="src short"
+	  ><span class="keyword"
+	    >data</span
+	    > <a href="#"
+	    >ThreeVars</a
+	    > a0 a b = <a href="#"
+	    >ThreeVars</a
+	    > a b</li
+	  ></ul
+	></div
+      ><div id="interface"
+      ><h1
+	>Documentation</h1
+	><div class="top"
+	><p class="src"
+	  ><span class="keyword"
+	    >class</span
+	    > <a id="t:Functor" class="def"
+	    >Functor</a
+	    > f <span class="keyword"
+	    >where</span
+	    > <a href="#" class="selflink"
+	    >#</a
+	    ></p
+	  ><div class="subs minimal"
+	  ><p class="caption"
+	    >Minimal complete definition</p
+	    ><p class="src"
+	    ><a href="#"
+	      >fmap</a
+	      ></p
+	    ></div
+	  ><div class="subs methods"
+	  ><p class="caption"
+	    >Methods</p
+	    ><p class="src"
+	    ><a id="v:fmap" class="def"
+	      >fmap</a
+	      > :: (a -&gt; b) -&gt; f a -&gt; f b <a href="#" class="selflink"
+	      >#</a
+	      ></p
+	    ></div
+	  ><div class="subs instances"
+	  ><p id="control.i:Functor" class="caption collapser" onclick="toggleSection('i:Functor')"
+	    >Instances</p
+	    ><div id="section.i:Functor" class="show"
+	    ><table
+	      ><tr
+		><td class="src clearfix"
+		  ><span class="inst-left"
+		    ><span id="control.i:ic:Functor:Functor:1" class="instance expander" onclick="toggleSection('i:ic:Functor:Functor:1')"
+		      ></span
+		      > <a href="#"
+		      >Functor</a
+		      > (<a href="#"
+		      >Either</a
+		      > a)</span
+		    > <a href="#" class="selflink"
+		    >#</a
+		    ></td
+		  ><td class="doc empty"
+		  ></td
+		  ></tr
+		><tr
+		><td colspan="2"
+		  ><div id="section.i:ic:Functor:Functor:1" class="inst-details hide"
+		    ><div class="subs methods"
+		      ><p class="caption"
+			>Methods</p
+			><p class="src"
+			><a href="#"
+			  >fmap</a
+			  > :: (a0 -&gt; b) -&gt; <a href="#"
+			  >Either</a
+			  > a a0 -&gt; <a href="#"
+			  >Either</a
+			  > a b <a href="#" class="selflink"
+			  >#</a
+			  ></p
+			></div
+		      ></div
+		    ></td
+		  ></tr
+		><tr
+		><td class="src clearfix"
+		  ><span class="inst-left"
+		    ><span id="control.i:ic:Functor:Functor:2" class="instance expander" onclick="toggleSection('i:ic:Functor:Functor:2')"
+		      ></span
+		      > <a href="#"
+		      >Functor</a
+		      > (<a href="#"
+		      >ThreeVars</a
+		      > a0 a)</span
+		    > <a href="#" class="selflink"
+		    >#</a
+		    ></td
+		  ><td class="doc empty"
+		  ></td
+		  ></tr
+		><tr
+		><td colspan="2"
+		  ><div id="section.i:ic:Functor:Functor:2" class="inst-details hide"
+		    ><div class="subs methods"
+		      ><p class="caption"
+			>Methods</p
+			><p class="src"
+			><a href="#"
+			  >fmap</a
+			  > :: (a1 -&gt; b) -&gt; <a href="#"
+			  >ThreeVars</a
+			  > a0 a a1 -&gt; <a href="#"
+			  >ThreeVars</a
+			  > a0 a b <a href="#" class="selflink"
+			  >#</a
+			  ></p
+			></div
+		      ></div
+		    ></td
+		  ></tr
+		></table
+	      ></div
+	    ></div
+	  ></div
+	><div class="top"
+	><p class="src"
+	  ><span class="keyword"
+	    >data</span
+	    > <a id="t:ThreeVars" class="def"
+	    >ThreeVars</a
+	    > a0 a b <a href="#" class="selflink"
+	    >#</a
+	    ></p
+	  ><div class="doc"
+	  ><p
+	    >Phantom type a0 is added to block the first renaming from a to a0. This ensures that the renamer doesn't create a new conflict</p
+	    ></div
+	  ><div class="subs constructors"
+	  ><p class="caption"
+	    >Constructors</p
+	    ><table
+	    ><tr
+	      ><td class="src"
+		><a id="v:ThreeVars" class="def"
+		  >ThreeVars</a
+		  > a b</td
+		><td class="doc empty"
+		></td
+		></tr
+	      ></table
+	    ></div
+	  ><div class="subs instances"
+	  ><p id="control.i:ThreeVars" class="caption collapser" onclick="toggleSection('i:ThreeVars')"
+	    >Instances</p
+	    ><div id="section.i:ThreeVars" class="show"
+	    ><table
+	      ><tr
+		><td class="src clearfix"
+		  ><span class="inst-left"
+		    ><span id="control.i:id:ThreeVars:Functor:1" class="instance expander" onclick="toggleSection('i:id:ThreeVars:Functor:1')"
+		      ></span
+		      > <a href="#"
+		      >Functor</a
+		      > (<a href="#"
+		      >ThreeVars</a
+		      > a0 a)</span
+		    > <a href="#" class="selflink"
+		    >#</a
+		    ></td
+		  ><td class="doc empty"
+		  ></td
+		  ></tr
+		><tr
+		><td colspan="2"
+		  ><div id="section.i:id:ThreeVars:Functor:1" class="inst-details hide"
+		    ><div class="subs methods"
+		      ><p class="caption"
+			>Methods</p
+			><p class="src"
+			><a href="#"
+			  >fmap</a
+			  > :: (a1 -&gt; b) -&gt; <a href="#"
+			  >ThreeVars</a
+			  > a0 a a1 -&gt; <a href="#"
+			  >ThreeVars</a
+			  > a0 a b <a href="#" class="selflink"
+			  >#</a
+			  ></p
+			></div
+		      ></div
+		    ></td
+		  ></tr
+		></table
+	      ></div
+	    ></div
+	  ></div
+	></div
+      ></div
+    ><div id="footer"
+    ></div
+    ></body
+  ></html
+>
\ No newline at end of file
diff --git a/html-test/ref/Instances.html b/html-test/ref/Instances.html
index b014e8df..c9ca6f82 100644
--- a/html-test/ref/Instances.html
+++ b/html-test/ref/Instances.html
@@ -102,9 +102,9 @@ window.onload = function () {pageLoad();};
 			  >&lt;~~</a
 			  > <a href="#"
 			  >Int</a
-			  >) -&gt; a -&gt; a <a href="#"
+			  >) -&gt; a0 -&gt; a <a href="#"
 			  >&lt;~~</a
-			  > a <a href="#" class="selflink"
+			  > a0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -114,7 +114,7 @@ window.onload = function () {pageLoad();};
 			  >&lt;~~</a
 			  > (a <a href="#"
 			  >&lt;~~</a
-			  > a)) -&gt; <a href="#"
+			  > a0)) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; a <a href="#"
 			  >&lt;~~</a
@@ -298,9 +298,9 @@ window.onload = function () {pageLoad();};
 			  >Either</a
 			  > a <a href="#"
 			  >Int</a
-			  > -&gt; a -&gt; <a href="#"
+			  > -&gt; a0 -&gt; <a href="#"
 			  >Either</a
-			  > a a <a href="#" class="selflink"
+			  > a a0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -310,7 +310,7 @@ window.onload = function () {pageLoad();};
 			  >Either</a
 			  > a (<a href="#"
 			  >Either</a
-			  > a a) -&gt; <a href="#"
+			  > a a0) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; <a href="#"
 			  >Either</a
@@ -356,13 +356,13 @@ window.onload = function () {pageLoad();};
 			  >foo</a
 			  > :: (f a, <a href="#"
 			  >Int</a
-			  >) -&gt; a -&gt; (f a, a) <a href="#" class="selflink"
+			  >) -&gt; a0 -&gt; (f a, a0) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >foo'</a
-			  > :: (f a, (f a, a)) -&gt; <a href="#"
+			  > :: (f a, (f a, a0)) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; (f a, (f a, <a href="#"
 			  >Int</a
@@ -402,9 +402,9 @@ window.onload = function () {pageLoad();};
 			  >&lt;~~</a
 			  > <a href="#"
 			  >Int</a
-			  >) -&gt; a -&gt; a <a href="#"
+			  >) -&gt; a0 -&gt; a <a href="#"
 			  >&lt;~~</a
-			  > a <a href="#" class="selflink"
+			  > a0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -414,7 +414,7 @@ window.onload = function () {pageLoad();};
 			  >&lt;~~</a
 			  > (a <a href="#"
 			  >&lt;~~</a
-			  > a)) -&gt; <a href="#"
+			  > a0)) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; a <a href="#"
 			  >&lt;~~</a
@@ -456,13 +456,13 @@ window.onload = function () {pageLoad();};
 			  >foo</a
 			  > :: (a, a, <a href="#"
 			  >Int</a
-			  >) -&gt; a -&gt; (a, a, a) <a href="#" class="selflink"
+			  >) -&gt; a0 -&gt; (a, a, a0) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >foo'</a
-			  > :: (a, a, (a, a, a)) -&gt; <a href="#"
+			  > :: (a, a, (a, a, a0)) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; (a, a, (a, a, <a href="#"
 			  >Int</a
@@ -502,9 +502,9 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b <a href="#"
 			  >Int</a
-			  > -&gt; a -&gt; <a href="#"
+			  > -&gt; a0 -&gt; <a href="#"
 			  >Quux</a
-			  > a b a <a href="#" class="selflink"
+			  > a b a0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -514,7 +514,7 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b (<a href="#"
 			  >Quux</a
-			  > a b a) -&gt; <a href="#"
+			  > a b a0) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; <a href="#"
 			  >Quux</a
@@ -562,11 +562,11 @@ window.onload = function () {pageLoad();};
 			  >LiftedRep</a
 			  >) a <a href="#"
 			  >Int</a
-			  > -&gt; a -&gt; (<a href="#"
+			  > -&gt; a0 -&gt; (<a href="#"
 			  >LiftedRep</a
 			  > -&gt; <a href="#"
 			  >LiftedRep</a
-			  >) a a <a href="#" class="selflink"
+			  >) a a0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -580,7 +580,7 @@ window.onload = function () {pageLoad();};
 			  >LiftedRep</a
 			  > -&gt; <a href="#"
 			  >LiftedRep</a
-			  >) a a) -&gt; <a href="#"
+			  >) a a0) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; (<a href="#"
 			  >LiftedRep</a
@@ -1002,19 +1002,19 @@ window.onload = function () {pageLoad();};
 			><p class="src"
 			><a href="#"
 			  >bar'</a
-			  > :: (a, b, (a, b, (a, b, a))) -&gt; (a, b, (a, b, (a, b, b))) <a href="#" class="selflink"
+			  > :: (a, b, (a, b, (a, b, a))) -&gt; (a, b, (a, b, (a, b, b0))) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >bar0</a
-			  > :: ((a, b, (a, b, a)), (a, b, (a, b, a))) -&gt; ((a, b, b), (a, b, c)) <a href="#" class="selflink"
+			  > :: ((a, b, (a, b, a)), (a, b, (a, b, a))) -&gt; ((a, b, b0), (a, b, c)) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >bar1</a
-			  > :: ((a, b, (a, b, a)), (a, b, (a, b, a))) -&gt; ((a, b, b), (a, b, c)) <a href="#" class="selflink"
+			  > :: ((a, b, (a, b, a)), (a, b, (a, b, a))) -&gt; ((a, b, b0), (a, b, c)) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1076,7 +1076,7 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a c (<a href="#"
 			  >Quux</a
-			  > a c b)) <a href="#" class="selflink"
+			  > a c b0)) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -1092,9 +1092,9 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b c)) -&gt; (<a href="#"
 			  >Quux</a
-			  > a c b, <a href="#"
+			  > a c b0, <a href="#"
 			  >Quux</a
-			  > a c c) <a href="#" class="selflink"
+			  > a c c0) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -1110,9 +1110,9 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b c)) -&gt; (<a href="#"
 			  >Quux</a
-			  > a c b, <a href="#"
+			  > a c b0, <a href="#"
 			  >Quux</a
-			  > a c c) <a href="#" class="selflink"
+			  > a c c0) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1202,7 +1202,7 @@ window.onload = function () {pageLoad();};
 			  >forall</span
 			  > a. a -&gt; a) -&gt; (b, <span class="keyword"
 			  >forall</span
-			  > a. a -&gt; [c]) -&gt; (b, c) <a href="#" class="selflink"
+			  > c0. c0 -&gt; [c]) -&gt; (b, c1) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -1222,9 +1222,9 @@ window.onload = function () {pageLoad();};
 			  >forall</span
 			  > b. (<span class="keyword"
 			  >forall</span
-			  > a. a -&gt; [c]) -&gt; c) -&gt; <span class="keyword"
+			  > b. b -&gt; [c]) -&gt; c0) -&gt; <span class="keyword"
 			  >forall</span
-			  > a. a -&gt; b <a href="#" class="selflink"
+			  > c1. c1 -&gt; b <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1256,31 +1256,31 @@ window.onload = function () {pageLoad();};
 			  >baz</a
 			  > :: (a -&gt; b) -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. c -&gt; c) -&gt; (b, <span class="keyword"
+			  > a0. a0 -&gt; a0) -&gt; (b0, <span class="keyword"
 			  >forall</span
-			  > c. c -&gt; a -&gt; b) -&gt; (b, c) <a href="#" class="selflink"
+			  > c. c -&gt; a -&gt; b) -&gt; (b0, c) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz'</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. c -&gt; a -&gt; b) -&gt; (<span class="keyword"
+			  > b1. b1 -&gt; a -&gt; b) -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. c -&gt; a -&gt; b) -&gt; [(b, a -&gt; b)] <a href="#" class="selflink"
+			  > b2. b2 -&gt; a -&gt; b) -&gt; [(b0, a -&gt; b)] <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz''</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. (<span class="keyword"
+			  > b1. (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; a -&gt; b) -&gt; c) -&gt; <span class="keyword"
+			  > b2. b2 -&gt; a -&gt; b) -&gt; c) -&gt; <span class="keyword"
 			  >forall</span
-			  > c. c -&gt; b <a href="#" class="selflink"
+			  > c. c -&gt; b0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1312,31 +1312,31 @@ window.onload = function () {pageLoad();};
 			  >baz</a
 			  > :: (a, b, c) -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; d) -&gt; (b, <span class="keyword"
+			  > a0. a0 -&gt; a0) -&gt; (b0, <span class="keyword"
 			  >forall</span
-			  > d. d -&gt; (a, b, c)) -&gt; (b, c) <a href="#" class="selflink"
+			  > c0. c0 -&gt; (a, b, c)) -&gt; (b0, c1) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz'</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; (a, b, c)) -&gt; (<span class="keyword"
+			  > b1. b1 -&gt; (a, b, c)) -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; (a, b, c)) -&gt; [(b, (a, b, c))] <a href="#" class="selflink"
+			  > b2. b2 -&gt; (a, b, c)) -&gt; [(b0, (a, b, c))] <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz''</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. (<span class="keyword"
+			  > b1. (<span class="keyword"
 			  >forall</span
-			  > e. e -&gt; (a, b, c)) -&gt; c) -&gt; <span class="keyword"
+			  > b2. b2 -&gt; (a, b, c)) -&gt; c0) -&gt; <span class="keyword"
 			  >forall</span
-			  > d. d -&gt; b <a href="#" class="selflink"
+			  > c1. c1 -&gt; b0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1372,25 +1372,25 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b c -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; d) -&gt; (b, <span class="keyword"
+			  > a0. a0 -&gt; a0) -&gt; (b0, <span class="keyword"
 			  >forall</span
-			  > d. d -&gt; <a href="#"
+			  > c0. c0 -&gt; <a href="#"
 			  >Quux</a
-			  > a b c) -&gt; (b, c) <a href="#" class="selflink"
+			  > a b c) -&gt; (b0, c1) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz'</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; <a href="#"
+			  > b1. b1 -&gt; <a href="#"
 			  >Quux</a
 			  > a b c) -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; <a href="#"
+			  > b2. b2 -&gt; <a href="#"
 			  >Quux</a
-			  > a b c) -&gt; [(b, <a href="#"
+			  > a b c) -&gt; [(b0, <a href="#"
 			  >Quux</a
 			  > a b c)] <a href="#" class="selflink"
 			  >#</a
@@ -1398,15 +1398,15 @@ window.onload = function () {pageLoad();};
 			><p class="src"
 			><a href="#"
 			  >baz''</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. (<span class="keyword"
+			  > b1. (<span class="keyword"
 			  >forall</span
-			  > e. e -&gt; <a href="#"
+			  > b2. b2 -&gt; <a href="#"
 			  >Quux</a
-			  > a b c) -&gt; c) -&gt; <span class="keyword"
+			  > a b c) -&gt; c0) -&gt; <span class="keyword"
 			  >forall</span
-			  > d. d -&gt; b <a href="#" class="selflink"
+			  > c1. c1 -&gt; b0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1438,31 +1438,31 @@ window.onload = function () {pageLoad();};
 			  >baz</a
 			  > :: (a, [b], b, a) -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. c -&gt; c) -&gt; (b, <span class="keyword"
+			  > a0. a0 -&gt; a0) -&gt; (b0, <span class="keyword"
 			  >forall</span
-			  > c. c -&gt; (a, [b], b, a)) -&gt; (b, c) <a href="#" class="selflink"
+			  > c. c -&gt; (a, [b], b, a)) -&gt; (b0, c) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz'</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. c -&gt; (a, [b], b, a)) -&gt; (<span class="keyword"
+			  > b1. b1 -&gt; (a, [b], b, a)) -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. c -&gt; (a, [b], b, a)) -&gt; [(b, (a, [b], b, a))] <a href="#" class="selflink"
+			  > b2. b2 -&gt; (a, [b], b, a)) -&gt; [(b0, (a, [b], b, a))] <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz''</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > c. (<span class="keyword"
+			  > b1. (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; (a, [b], b, a)) -&gt; c) -&gt; <span class="keyword"
+			  > b2. b2 -&gt; (a, [b], b, a)) -&gt; c) -&gt; <span class="keyword"
 			  >forall</span
-			  > c. c -&gt; b <a href="#" class="selflink"
+			  > c. c -&gt; b0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1546,9 +1546,9 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b <a href="#"
 			  >Int</a
-			  > -&gt; a -&gt; <a href="#"
+			  > -&gt; a0 -&gt; <a href="#"
 			  >Quux</a
-			  > a b a <a href="#" class="selflink"
+			  > a b a0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -1558,7 +1558,7 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b (<a href="#"
 			  >Quux</a
-			  > a b a) -&gt; <a href="#"
+			  > a b a0) -&gt; <a href="#"
 			  >Int</a
 			  > -&gt; <a href="#"
 			  >Quux</a
@@ -1628,7 +1628,7 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a c (<a href="#"
 			  >Quux</a
-			  > a c b)) <a href="#" class="selflink"
+			  > a c b0)) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -1644,9 +1644,9 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b c)) -&gt; (<a href="#"
 			  >Quux</a
-			  > a c b, <a href="#"
+			  > a c b0, <a href="#"
 			  >Quux</a
-			  > a c c) <a href="#" class="selflink"
+			  > a c c0) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
@@ -1662,9 +1662,9 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b c)) -&gt; (<a href="#"
 			  >Quux</a
-			  > a c b, <a href="#"
+			  > a c b0, <a href="#"
 			  >Quux</a
-			  > a c c) <a href="#" class="selflink"
+			  > a c c0) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
@@ -1700,25 +1700,25 @@ window.onload = function () {pageLoad();};
 			  >Quux</a
 			  > a b c -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; d) -&gt; (b, <span class="keyword"
+			  > a0. a0 -&gt; a0) -&gt; (b0, <span class="keyword"
 			  >forall</span
-			  > d. d -&gt; <a href="#"
+			  > c0. c0 -&gt; <a href="#"
 			  >Quux</a
-			  > a b c) -&gt; (b, c) <a href="#" class="selflink"
+			  > a b c) -&gt; (b0, c1) <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			><p class="src"
 			><a href="#"
 			  >baz'</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; <a href="#"
+			  > b1. b1 -&gt; <a href="#"
 			  >Quux</a
 			  > a b c) -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. d -&gt; <a href="#"
+			  > b2. b2 -&gt; <a href="#"
 			  >Quux</a
-			  > a b c) -&gt; [(b, <a href="#"
+			  > a b c) -&gt; [(b0, <a href="#"
 			  >Quux</a
 			  > a b c)] <a href="#" class="selflink"
 			  >#</a
@@ -1726,15 +1726,15 @@ window.onload = function () {pageLoad();};
 			><p class="src"
 			><a href="#"
 			  >baz''</a
-			  > :: b -&gt; (<span class="keyword"
+			  > :: b0 -&gt; (<span class="keyword"
 			  >forall</span
-			  > d. (<span class="keyword"
+			  > b1. (<span class="keyword"
 			  >forall</span
-			  > e. e -&gt; <a href="#"
+			  > b2. b2 -&gt; <a href="#"
 			  >Quux</a
-			  > a b c) -&gt; c) -&gt; <span class="keyword"
+			  > a b c) -&gt; c0) -&gt; <span class="keyword"
 			  >forall</span
-			  > d. d -&gt; b <a href="#" class="selflink"
+			  > c1. c1 -&gt; b0 <a href="#" class="selflink"
 			  >#</a
 			  ></p
 			></div
diff --git a/html-test/src/Bug613.hs b/html-test/src/Bug613.hs
new file mode 100644
index 00000000..effef695
--- /dev/null
+++ b/html-test/src/Bug613.hs
@@ -0,0 +1,16 @@
+module Bug613  where
+
+import Prelude (Either(Left, Right))
+
+class Functor f where
+  fmap :: (a -> b) -> f a -> f b
+
+instance Functor (Either a) where
+  fmap _ (Left x) = Left x
+  fmap f (Right y) = Right (f y)
+
+-- | Phantom type a0 is added to block the first renaming from a to a0. This ensures that the renamer doesn't create a new conflict
+data ThreeVars a0 a b = ThreeVars a b
+
+instance Functor (ThreeVars a0 a) where
+  fmap f (ThreeVars a b) = ThreeVars a (f b)