Big tidy-up of deriving code

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

diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs
index 480357e..d81278a 100644 (file)
--- a/compiler/types/Type.lhs
+++ b/compiler/types/Type.lhs
@@ -55,6 +55,7 @@ module Type (
 
        -- Source types
        predTypeRep, mkPredTy, mkPredTys,
+       tyConOrigHead,
 
        -- Newtypes
        splitRecNewType_maybe, newTyConInstRhs,
@@ -91,7 +92,7 @@ module Type (
 
        -- Performing substitution on types
        substTy, substTys, substTyWith, substTheta, 
-       substPred, substTyVar, substTyVarBndr, deShadowTy, lookupTyVar,
+       substPred, substTyVar, substTyVars, substTyVarBndr, deShadowTy, lookupTyVar,
 
        -- Pretty-printing
        pprType, pprParendType, pprTyThingCategory, pprForAll,
@@ -410,7 +411,6 @@ splitNewTyConApp_maybe other              = Nothing
 newTyConInstRhs :: TyCon -> [Type] -> Type
 newTyConInstRhs tycon tys =
     let (tvs, ty) = newTyConRhs tycon in substTyWith tvs tys ty
-
 \end{code}
 
 
@@ -602,6 +602,13 @@ 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}
 
 
@@ -1305,6 +1312,9 @@ substTyVar subst@(TvSubst in_scope env) tv
                Just ty -> ty   -- See Note [Apply Once]
     } 
 
+substTyVars :: TvSubst -> [TyVar] -> [Type]
+substTyVars subst tvs = map (substTyVar subst) tvs
+
 lookupTyVar :: TvSubst -> TyVar  -> Maybe Type
        -- See Note [Extending the TvSubst]
 lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv