Deriving for indexed data types

[ghc-hetmet.git] / compiler / types / Type.lhs

diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs
index de0215e..cdc54a1 100644 (file)
--- a/compiler/types/Type.lhs
+++ b/compiler/types/Type.lhs
@@ -48,13 +48,14 @@ module Type (
        splitTyConApp_maybe, splitTyConApp, 
         splitNewTyConApp_maybe, splitNewTyConApp,
 
-       repType, typePrimRep, coreView, tcView, kindView,
+       repType, repType', typePrimRep, coreView, tcView, kindView,
 
        mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys, 
        applyTy, applyTys, isForAllTy, dropForAlls,
 
        -- Source types
        predTypeRep, mkPredTy, mkPredTys,
+       tyConOrigHead,
 
        -- Newtypes
        splitRecNewType_maybe, newTyConInstRhs,
@@ -457,6 +458,16 @@ repType (TyConApp tc tys)
                           repType (new_type_rep tc tys)
 repType ty = ty
 
+-- repType' aims to be a more thorough version of repType
+-- For now it simply looks through the TyConApp args too
+repType' ty -- | pprTrace "repType'" (ppr ty $$ ppr (go1 ty)) False = undefined
+            | otherwise = go1 ty 
+ where 
+        go1 = go . repType
+        go (TyConApp tc tys) = mkTyConApp tc (map repType' tys)
+        go ty = ty
+
+
 -- new_type_rep doesn't ask any questions: 
 -- it just expands newtype, whether recursive or not
 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
@@ -592,6 +603,13 @@ predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
        -- Result might be a newtype application, but the consumer will
        -- look through that too if necessary
 predTypeRep (EqPred ty1 ty2) = pprPanic "predTypeRep" (ppr (EqPred ty1 ty2))
+
+-- The original head is the tycon and its variables for a vanilla tycon and it
+-- is the family tycon and its type indexes for a family instance.
+tyConOrigHead :: TyCon -> (TyCon, [Type])
+tyConOrigHead tycon = case tyConFamInst_maybe tycon of
+                       Nothing      -> (tycon, mkTyVarTys (tyConTyVars tycon))
+                       Just famInst -> famInst
 \end{code}