Type families: new algorithm to solve equalities

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

diff --git a/compiler/types/Type.lhs b/compiler/types/Type.lhs
index 63633e9..d80bd52 100644 (file)
--- a/compiler/types/Type.lhs
+++ b/compiler/types/Type.lhs
@@ -39,7 +39,7 @@ module Type (
         splitNewTyConApp_maybe, splitNewTyConApp,
 
         mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys, 
-       applyTy, applyTys, isForAllTy, dropForAlls,
+       applyTy, applyTys, applyTysD, isForAllTy, dropForAlls,
        
        -- (Newtypes)
        newTyConInstRhs,
@@ -128,7 +128,7 @@ module Type (
         isEmptyTvSubst,
 
        -- ** Performing substitution on types
-       substTy, substTys, substTyWith, substTheta, 
+       substTy, substTys, substTyWith, substTysWith, substTheta, 
        substPred, substTyVar, substTyVars, substTyVarBndr, deShadowTy, lookupTyVar,
 
        -- * Pretty-printing
@@ -742,15 +742,18 @@ applyTys :: Type -> [Type] -> Type
 -- > foo = case undefined :: R of
 -- >            R f -> f ()
 
-applyTys orig_fun_ty []      = orig_fun_ty
-applyTys orig_fun_ty arg_tys 
+applyTys ty args = applyTysD empty ty args
+
+applyTysD :: SDoc -> Type -> [Type] -> Type    -- Debug version
+applyTysD _   orig_fun_ty []      = orig_fun_ty
+applyTysD doc orig_fun_ty arg_tys 
   | n_tvs == n_args    -- The vastly common case
   = substTyWith tvs arg_tys rho_ty
   | n_tvs > n_args     -- Too many for-alls
   = substTyWith (take n_args tvs) arg_tys 
                (mkForAllTys (drop n_args tvs) rho_ty)
   | otherwise          -- Too many type args
-  = ASSERT2( n_tvs > 0, ppr orig_fun_ty )      -- Zero case gives infnite loop!
+  = ASSERT2( n_tvs > 0, doc $$ ppr orig_fun_ty )       -- Zero case gives infnite loop!
     applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
             (drop n_tvs arg_tys)
   where
@@ -1511,6 +1514,12 @@ substTyWith :: [TyVar] -> [Type] -> Type -> Type
 substTyWith tvs tys = ASSERT( length tvs == length tys )
                      substTy (zipOpenTvSubst tvs tys)
 
+-- | Type substitution making use of an 'TvSubst' that
+-- is assumed to be open, see 'zipOpenTvSubst'
+substTysWith :: [TyVar] -> [Type] -> [Type] -> [Type]
+substTysWith tvs tys = ASSERT( length tvs == length tys )
+                      substTys (zipOpenTvSubst tvs tys)
+
 -- | Substitute within a 'Type'
 substTy :: TvSubst -> Type  -> Type
 substTy subst ty | isEmptyTvSubst subst = ty