diff --git a/checks/Check.hs b/checks/Check.hs
index 94f7fcd..1ee80eb 100644
--- a/checks/Check.hs
+++ b/checks/Check.hs
@@ -299,19 +299,34 @@ foldUnionVarsBK
 checkPlainVarUsage :: forall m. (MonadIO m, Die m, CSMR m) => NameAttr -> (Meta, ParItems (BK, UsageLabel)) -> m ()
 checkPlainVarUsage sharedAttr (m, p) = check p
   where
-    addBK :: BK -> Vars -> VarsBK
-    addBK bk vs = VarsBK (Map.fromAscList $ zip (Set.toAscList $ readVars vs) (repeat bk))
-                         ((Map.map (\me -> (maybeToList me, bk)) $ writtenVars vs)
-                          `Map.union` Map.fromAscList (zip (Set.toAscList $ usedVars
-                            vs) (repeat ([], bk))))
+    addBK :: BK -> Vars -> m VarsBK
+    addBK bk vs
+      = do let read = Map.fromAscList $ zip (Set.toAscList $ readVars vs) (repeat bk)
+           splitUsed <- splitEnds' $ Set.toList $ usedVars vs
+           splitWritten <- concatMapM splitEnds (Map.toList $ writtenVars vs) >>* Map.fromList
+           let used = Map.fromList (zip splitUsed (repeat ([], bk)))
+           return $ VarsBK read
+                      ((Map.map (\me -> (maybeToList me, bk)) splitWritten)
+                         `Map.union` used)
+
+    splitEnds' = liftM (map fst) . concatMapM splitEnds . flip zip (repeat ())
+
+    splitEnds :: (Var, a) -> m [(Var, a)]
+    splitEnds (Var v, x)
+      = do t <- astTypeOf v
+           case t of
+             A.Chan {} -> return
+               [(Var $ A.DirectedVariable (findMeta v) dir v, x)
+               | dir <- [A.DirInput, A.DirOutput]]
+             _ -> return [(Var v, x)]
 
     reps (RepParItem r p) = r : reps p
     reps (SeqItems _) = []
     reps (ParItems ps) = concatMap reps ps
 
-    getVars :: ParItems (BK, UsageLabel) -> Map.Map Var (Maybe BK, Maybe BK)
-    getVars (SeqItems ss) = foldUnionVarsBK $ [addBK bk $ nodeVars u | (bk, u) <- ss]
-    getVars (ParItems ps) = foldl (Map.unionWith join) Map.empty (map getVars ps)
+    getVars :: ParItems (BK, UsageLabel) -> m (Map.Map Var (Maybe BK, Maybe BK))
+    getVars (SeqItems ss) = liftM foldUnionVarsBK $ sequence [addBK bk $ nodeVars u | (bk, u) <- ss]
+    getVars (ParItems ps) = liftM (foldl (Map.unionWith join) Map.empty) (mapM getVars ps)
       where
         join a b = (f (fst a) (fst b), f (snd a) (snd b))
         f Nothing x = x
@@ -344,13 +359,21 @@ checkPlainVarUsage sharedAttr (m, p) = check p
     -- A quick way to do this is to do a fold-union across all the maps, turning
     -- the values into lists that can then be scanned for any problems.
     check (ParItems ps)
-      = do sharedNames <- getCompState >>* csNameAttr >>* Map.filter (Set.member sharedAttr)
-             >>* Map.keysSet >>* (Set.map $ UsageCheckUtils.Var . A.Variable emptyMeta . A.Name emptyMeta)
+      = do rawSharedNames <- getCompState >>* csNameAttr >>* Map.filter (Set.member sharedAttr)
+             >>* Map.keysSet
+           -- We add in the directed versions of each (channel or not) so that
+           -- we make sure to ignore c? when c is shared:
+           let allSharedNames
+                 = Set.fromList $ concatMap (map UsageCheckUtils.Var .
+                    flip applyAll [id, A.DirectedVariable emptyMeta A.DirInput
+                                     , A.DirectedVariable emptyMeta A.DirOutput]
+                    . A.Variable emptyMeta . A.Name emptyMeta) $ Set.toList rawSharedNames
            let decl = concatMap getDecl ps
            filt <- filterPlain
+           vars <- mapM getVars ps
            let examineVars =
-                 map (filterMapByKey filt . (`difference` (Set.fromList decl `Set.union` sharedNames)))
-                   (map getVars ps)
+                 map (filterMapByKey filt . (`difference` (Set.fromList decl `Set.union` allSharedNames)))
+                   vars
            checkCREW examineVars
       where
         difference m s = m `Map.difference` (Map.fromAscList $ zip (Set.toAscList
diff --git a/frontends/OccamPasses.hs b/frontends/OccamPasses.hs
index 4b0433f..5aa1778 100644
--- a/frontends/OccamPasses.hs
+++ b/frontends/OccamPasses.hs
@@ -147,6 +147,8 @@ checkConstants = occamOnlyPass "Check mandatory constants"
               return o
     doOption o = return o
 
+-- | Turns things like cs[0]? into cs?[0], which helps later on in the usage checking
+-- (as we can consider cs? a different array than cs!).
 pushUpDirections :: Pass
 pushUpDirections = occamOnlyPass "Push up direction specifiers on arrays"
   [] []
diff --git a/frontends/OccamTypes.hs b/frontends/OccamTypes.hs
index a79bae9..270639f 100644
--- a/frontends/OccamTypes.hs
+++ b/frontends/OccamTypes.hs
@@ -769,6 +769,8 @@ inferTypes = occamOnlyPass "Infer types"
                     A.Array _ (A.ChanEnd dir _ _) ->
                                          do v'' <- makeEnd m dir v'
                                             return (t', v'')
+                    -- TODO infer direction of IS channel type
+                    -- We will need the body!
                     _ -> return (t', v')
                   return $ A.Is m am' t'' v''
             A.IsExpr m am t e ->