X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGadt.lhs;h=48b2b0623cd6455cba11c982be5e06cdc096cdfe;hb=4cf7988f740ee799bbdb0b6e653c096099378085;hp=4c1f70ecf153e8a44a09bcc4d17c9657527b3f35;hpb=7a327c1297615a9498e7117a0017b09ff2458d53;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs
index 4c1f70e..48b2b06 100644
--- a/compiler/typecheck/TcGadt.lhs
+++ b/compiler/typecheck/TcGadt.lhs
@@ -10,10 +10,17 @@
 %************************************************************************
 
 \begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
 module TcGadt (
-	Refinement, emptyRefinement, gadtRefine, 
-	refineType, refineResType,
-	dataConCanMatch,
+	Refinement, emptyRefinement, isEmptyRefinement, 
+	gadtRefine, 
+	refineType, refinePred, refineResType,
 	tcUnifyTys, BindFlag(..)
   ) where
 
@@ -22,8 +29,8 @@ module TcGadt (
 import HsSyn
 import Coercion
 import Type
+
 import TypeRep
-import DataCon
 import Var
 import VarEnv
 import VarSet
@@ -32,11 +39,8 @@ import Maybes
 import Control.Monad
 import Outputable
 import TcType
-
-#ifdef DEBUG
 import Unique
 import UniqFM
-#endif
 \end{code}
 
 
@@ -61,6 +65,8 @@ instance Outputable Refinement where
 emptyRefinement :: Refinement
 emptyRefinement = (Reft emptyInScopeSet emptyVarEnv)
 
+isEmptyRefinement :: Refinement -> Bool
+isEmptyRefinement (Reft _ env) = isEmptyVarEnv env
 
 refineType :: Refinement -> Type -> Maybe (Coercion, Type)
 -- Apply the refinement to the type.
@@ -77,6 +83,17 @@ refineType (Reft in_scope env) ty
     tv_subst = mkTvSubst in_scope (mapVarEnv snd env)
     co_subst = mkTvSubst in_scope (mapVarEnv fst env)
  
+refinePred :: Refinement -> PredType -> Maybe (Coercion, PredType)
+refinePred (Reft in_scope env) pred
+  | not (isEmptyVarEnv env),		-- Common case
+    any (`elemVarEnv` env) (varSetElems (tyVarsOfPred pred))
+  = Just (mkPredTy (substPred co_subst pred), substPred tv_subst pred)
+  | otherwise
+  = Nothing	-- The type doesn't mention any refined type variables
+  where
+    tv_subst = mkTvSubst in_scope (mapVarEnv snd env)
+    co_subst = mkTvSubst in_scope (mapVarEnv fst env)
+ 
 refineResType :: Refinement -> Type -> (HsWrapper, Type)
 -- Like refineType, but returns the 'sym' coercion
 -- If (refineResType r ty) = (co, ty')
@@ -169,7 +186,7 @@ gadtRefine (Reft in_scope env1)
     do_one reft co_var = unify reft (TyVarTy co_var) ty1 ty2
 	where
 	   (ty1,ty2) = splitCoercionKind (tyVarKind co_var)
-\end{code} 
+\end{code}
 
 %************************************************************************
 %*									*
@@ -220,36 +237,21 @@ fixTvCoEnv in_scope env
       -- then use transitivity with the original coercion
 
 -----------------------------
+-- XXX Can we do this more nicely, by exploiting laziness?
+-- Or avoid needing it in the first place?
 fixTvSubstEnv :: InScopeSet -> TvSubstEnv -> TvSubstEnv
-fixTvSubstEnv in_scope env
-  = fixpt 
-  where
-    fixpt = mapVarEnv (substTy (mkTvSubst in_scope fixpt)) env
-
-----------------------------
-dataConCanMatch :: [Type] -> DataCon -> Bool
--- Returns True iff the data con can match a scrutinee of type (T tys)
---		    where T is the type constructor for the data con
---
--- Instantiate the equations and try to unify them
-dataConCanMatch tys con
-  | null eq_spec      = True	-- Common
-  | all isTyVarTy tys = True	-- Also common
-  | otherwise
-  = isJust (tcUnifyTys (\tv -> BindMe) 
-	   	       (map (substTyVar subst . fst) eq_spec)
-		       (map snd eq_spec))
+fixTvSubstEnv in_scope env = f env
   where
-    dc_tvs  = dataConUnivTyVars con
-    eq_spec = dataConEqSpec con
-    subst   = zipTopTvSubst dc_tvs tys
+    f e = let e' = mapUFM (substTy (mkTvSubst in_scope e)) e
+          in if and $ eltsUFM $ intersectUFM_C tcEqType e e'
+             then e
+             else f e'
 
 ----------------------------
 tryToBind :: TyVarSet -> TyVar -> BindFlag
 tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe
 		    | otherwise	             = AvoidMe
 
-
 \end{code}
 
 
@@ -260,7 +262,6 @@ tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe
 %************************************************************************
 
 \begin{code}
-#ifdef DEBUG
 badReftElts :: InternalReft -> [(Unique, (Coercion,Type))]
 -- Return the BAD elements of the refinement
 -- Should be empty; used in asserions only
@@ -273,7 +274,6 @@ badReftElts env
 		     | otherwise = False
 	where
 	  (ty1,ty2) = coercionKind co
-#endif
 
 emptyInternalReft :: InternalReft
 emptyInternalReft = emptyVarEnv