X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGadt.lhs;h=48b2b0623cd6455cba11c982be5e06cdc096cdfe;hb=288213d7c2c65fa68ca466c1a1a3378e24fa1151;hp=4129df5a1af44074cebf69b93f56c806028bd62c;hpb=1166c7d62f3fa9acd2084c90df6585cbbf868ceb;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs
index 4129df5..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
 
@@ -21,8 +28,9 @@ module TcGadt (
 
 import HsSyn
 import Coercion
+import Type
+
 import TypeRep
-import DataCon
 import Var
 import VarEnv
 import VarSet
@@ -30,12 +38,9 @@ import ErrUtils
 import Maybes
 import Control.Monad
 import Outputable
-
-#ifdef DEBUG
+import TcType
 import Unique
 import UniqFM
-import TcType
-#endif
 \end{code}
 
 
@@ -47,6 +52,8 @@ import TcType
 
 \begin{code}
 data Refinement = Reft InScopeSet InternalReft 
+
+type InternalReft = TyVarEnv (Coercion, Type)
 -- INVARIANT:   a->(co,ty)   then   co :: (a:=:ty)
 -- Not necessarily idemopotent
 
@@ -58,6 +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.
@@ -74,6 +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')
@@ -139,7 +159,7 @@ gadtRefine (Reft in_scope env1)
 	   ex_tvs co_vars
 -- Precondition: fvs( co_vars ) # env1
 -- That is, the kinds of the co_vars are a
--- fixed point of the  incoming refinement
+-- fixed point of the incoming refinement
 
   = ASSERT2( not $ any (`elemVarEnv` env1) (varSetElems $ tyVarsOfTypes $ map tyVarKind co_vars),
 	     ppr env1 $$ ppr co_vars $$ ppr (map tyVarKind co_vars) )
@@ -157,14 +177,16 @@ gadtRefine (Reft in_scope env1)
   where
     tv_set = mkVarSet ex_tvs
     in_scope' = foldr extend in_scope co_vars
+
+	-- For each co_var, add it *and* the tyvars it mentions, to in_scope
     extend co_var in_scope
-	= extendInScopeSetSet (extendInScopeSet in_scope co_var)
-			      (tyVarsOfType (tyVarKind co_var))
+	= extendInScopeSetSet in_scope $
+	  extendVarSet (tyVarsOfType (tyVarKind co_var)) co_var
 	
     do_one reft co_var = unify reft (TyVarTy co_var) ty1 ty2
 	where
 	   (ty1,ty2) = splitCoercionKind (tyVarKind co_var)
-\end{code} 
+\end{code}
 
 %************************************************************************
 %*									*
@@ -215,33 +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 :: 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))
+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}
 
 
@@ -252,12 +262,6 @@ tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe
 %************************************************************************
 
 \begin{code}
-type InternalReft = TyVarEnv (Coercion, Type)
-
--- INVARIANT:   a->(co,ty)   then   co :: (a:=:ty)
--- Not necessarily idemopotent
-
-#ifdef DEBUG
 badReftElts :: InternalReft -> [(Unique, (Coercion,Type))]
 -- Return the BAD elements of the refinement
 -- Should be empty; used in asserions only
@@ -270,7 +274,6 @@ badReftElts env
 		     | otherwise = False
 	where
 	  (ty1,ty2) = coercionKind co
-#endif
 
 emptyInternalReft :: InternalReft
 emptyInternalReft = emptyVarEnv