X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGadt.lhs;h=3761c68fada484fa600e215005bb306fbcaf7f36;hb=2423c249f5ca7785d0ec89eb33e72662da7561c1;hp=4129df5a1af44074cebf69b93f56c806028bd62c;hpb=1166c7d62f3fa9acd2084c90df6585cbbf868ceb;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs
index 4129df5..3761c68 100644
--- a/compiler/typecheck/TcGadt.lhs
+++ b/compiler/typecheck/TcGadt.lhs
@@ -11,8 +11,9 @@
 
 \begin{code}
 module TcGadt (
-	Refinement, emptyRefinement, gadtRefine, 
-	refineType, refineResType,
+	Refinement, emptyRefinement, isEmptyRefinement, 
+	gadtRefine, 
+	refineType, refinePred, refineResType,
 	dataConCanMatch,
 	tcUnifyTys, BindFlag(..)
   ) where
@@ -21,6 +22,8 @@ module TcGadt (
 
 import HsSyn
 import Coercion
+import Type
+
 import TypeRep
 import DataCon
 import Var
@@ -30,11 +33,11 @@ import ErrUtils
 import Maybes
 import Control.Monad
 import Outputable
+import TcType
 
 #ifdef DEBUG
 import Unique
 import UniqFM
-import TcType
 #endif
 \end{code}
 
@@ -47,6 +50,8 @@ 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 +63,8 @@ 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 +81,17 @@ 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 +157,7 @@ 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 +175,16 @@ 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}
 
 %************************************************************************
 %*									*
@@ -222,12 +242,15 @@ fixTvSubstEnv in_scope env
     fixpt = mapVarEnv (substTy (mkTvSubst in_scope fixpt)) env
 
 ----------------------------
-dataConCanMatch :: DataCon -> [Type] -> Bool
+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 con tys
+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))
@@ -252,11 +275,6 @@ 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