X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGadt.lhs;h=9d2658d103fd8b530f3b9edcc8a4306130ca7f88;hp=5bad13e0a4bf0e043be38a0fef55da50e9d1289d;hb=17b297d97d327620ed6bfab942f8992b2446f1bf;hpb=0d1fca153fa5426d793a4b16acdf57e409b9193f

diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs
index 5bad13e..9d2658d 100644
--- a/compiler/typecheck/TcGadt.lhs
+++ b/compiler/typecheck/TcGadt.lhs
@@ -10,10 +10,17 @@
 %************************************************************************
 
 \begin{code}
+{-# OPTIONS_GHC -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/WorkingConventions#Warnings
+-- for details
+
 module TcGadt (
-	Refinement, emptyRefinement, gadtRefine, 
-	refineType, refineResType,
-	dataConCanMatch,
+	Refinement, emptyRefinement, isEmptyRefinement, 
+	gadtRefine, 
+	refineType, refinePred, refineResType,
 	tcUnifyTys, BindFlag(..)
   ) where
 
@@ -21,8 +28,9 @@ module TcGadt (
 
 import HsSyn
 import Coercion
+import Type
+
 import TypeRep
-import DataCon
 import Var
 import VarEnv
 import VarSet
@@ -60,6 +68,8 @@ 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.
@@ -76,6 +86,17 @@ 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')
@@ -168,7 +189,7 @@ 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}
 
 %************************************************************************
 %*									*
@@ -226,26 +247,10 @@ fixTvSubstEnv in_scope env
     fixpt = mapVarEnv (substTy (mkTvSubst in_scope fixpt)) env
 
 ----------------------------
-dataConCanMatch :: DataCon -> [Type] -> 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 con tys
-  = isJust (tcUnifyTys (\tv -> BindMe) 
-	   	       (map (substTyVar subst . fst) eq_spec)
-		       (map snd eq_spec))
-  where
-    dc_tvs  = dataConUnivTyVars con
-    eq_spec = dataConEqSpec con
-    subst   = zipTopTvSubst dc_tvs tys
-
-----------------------------
 tryToBind :: TyVarSet -> TyVar -> BindFlag
 tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe
 		    | otherwise	             = AvoidMe
 
-
 \end{code}