X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGadt.lhs;h=48b2b0623cd6455cba11c982be5e06cdc096cdfe;hb=72d043c04c1b0db0896e2c876a1544434f0428ec;hp=3761c68fada484fa600e215005bb306fbcaf7f36;hpb=e68a891932d615590d9b1ab5752ada8142db5053;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs
index 3761c68..48b2b06 100644
--- a/compiler/typecheck/TcGadt.lhs
+++ b/compiler/typecheck/TcGadt.lhs
@@ -10,11 +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, isEmptyRefinement, 
 	gadtRefine, 
 	refineType, refinePred, refineResType,
-	dataConCanMatch,
 	tcUnifyTys, BindFlag(..)
   ) where
 
@@ -25,7 +31,6 @@ import Coercion
 import Type
 
 import TypeRep
-import DataCon
 import Var
 import VarEnv
 import VarSet
@@ -34,11 +39,8 @@ import Maybes
 import Control.Monad
 import Outputable
 import TcType
-
-#ifdef DEBUG
 import Unique
 import UniqFM
-#endif
 \end{code}
 
 
@@ -235,36 +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}
 
 
@@ -275,7 +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
@@ -288,7 +274,6 @@ badReftElts env
 		     | otherwise = False
 	where
 	  (ty1,ty2) = coercionKind co
-#endif
 
 emptyInternalReft :: InternalReft
 emptyInternalReft = emptyVarEnv