X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGadt.lhs;h=5bad13e0a4bf0e043be38a0fef55da50e9d1289d;hb=f515d87a510f9cd3d416d83e95e6e0f0298f7d18;hp=87f2c8db957efc1985d5a47fd7d0102ea5179720;hpb=e6d057711f4d6d6ff6342c39fa2b9e44d25447f1;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs
index 87f2c8d..5bad13e 100644
--- a/compiler/typecheck/TcGadt.lhs
+++ b/compiler/typecheck/TcGadt.lhs
@@ -1,4 +1,5 @@
 %
+% (c) The University of Glasgow 2006
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
 
@@ -16,29 +17,25 @@ module TcGadt (
 	tcUnifyTys, BindFlag(..)
   ) where
 
-import HsSyn	( HsWrapper(..), idHsWrapper, isIdHsWrapper )
-import Coercion	( Coercion, mkSymCoercion, mkTransCoercion, mkUnsafeCoercion,
-		  mkLeftCoercion, mkRightCoercion, mkCoKind, coercionKindPredTy,
-		  splitCoercionKind, decomposeCo, coercionKind )
-import TcType	( TvSubst(..), TvSubstEnv, substTy, mkTvSubst, 
-		  substTyVar, zipTopTvSubst, typeKind,
-		  eqKind, isSubKind, repSplitAppTy_maybe,
-		  tcView, tcGetTyVar_maybe
-		)
-import Type	( Type, tyVarsOfType, tyVarsOfTypes, tcEqType, mkTyVarTy )
-import TypeRep	( Type(..), PredType(..) )
-import DataCon	( DataCon, dataConUnivTyVars, dataConEqSpec )
-import Var	( CoVar, TyVar, tyVarKind, varUnique )
+#include "HsVersions.h"
+
+import HsSyn
+import Coercion
+import TypeRep
+import DataCon
+import Var
 import VarEnv
 import VarSet
-import ErrUtils		( Message )
-import Maybes		( MaybeErr(..), isJust )
-import Control.Monad	( foldM )
+import ErrUtils
+import Maybes
+import Control.Monad
 import Outputable
-import Unique		( Unique )
-import UniqFM		( ufmToList )
+import TcType
 
-#include "HsVersions.h"
+#ifdef DEBUG
+import Unique
+import UniqFM
+#endif
 \end{code}
 
 
@@ -50,6 +47,8 @@ import UniqFM		( ufmToList )
 
 \begin{code}
 data Refinement = Reft InScopeSet InternalReft 
+
+type InternalReft = TyVarEnv (Coercion, Type)
 -- INVARIANT:   a->(co,ty)   then   co :: (a:=:ty)
 -- Not necessarily idemopotent
 
@@ -62,16 +61,17 @@ emptyRefinement :: Refinement
 emptyRefinement = (Reft emptyInScopeSet emptyVarEnv)
 
 
-refineType :: Refinement -> Type -> (HsWrapper, Type)
+refineType :: Refinement -> Type -> Maybe (Coercion, Type)
 -- Apply the refinement to the type.
 -- If (refineType r ty) = (co, ty')
 -- Then co :: ty:=:ty'
+-- Nothing => the refinement does nothing to this type
 refineType (Reft in_scope env) ty
   | not (isEmptyVarEnv env),		-- Common case
     any (`elemVarEnv` env) (varSetElems (tyVarsOfType ty))
-  = (WpCo (substTy co_subst ty), substTy tv_subst ty)
+  = Just (substTy co_subst ty, substTy tv_subst ty)
   | otherwise
-  = (idHsWrapper, ty)	-- The type doesn't mention any refined type variables
+  = 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)
@@ -80,11 +80,11 @@ refineResType :: Refinement -> Type -> (HsWrapper, Type)
 -- Like refineType, but returns the 'sym' coercion
 -- If (refineResType r ty) = (co, ty')
 -- Then co :: ty':=:ty
+-- It's convenient to return a HsWrapper here
 refineResType reft ty
   = case refineType reft ty of
-	(WpCo co, ty1) -> (WpCo (mkSymCoercion co), ty1)
-	(id_co,   ty1) -> ASSERT( isIdHsWrapper id_co )
-			  (idHsWrapper, ty1)
+	Just (co, ty1) -> (WpCo (mkSymCoercion co), ty1)
+	Nothing	       -> (idHsWrapper, 	    ty)
 \end{code}
 
 
@@ -141,7 +141,7 @@ 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) )
@@ -159,9 +159,11 @@ 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
@@ -208,15 +210,13 @@ fixTvCoEnv in_scope env
   where
     fixpt         = mapVarEnv step env
 
-    step (co, ty) = (co1, ty')
+    step (co, ty) = case refineType (Reft in_scope fixpt) ty of
+			Nothing 	-> (co, 		    ty)
+			Just (co', ty') -> (mkTransCoercion co co', ty')
       -- Apply fixpt one step:
       -- Use refineType to get a substituted type, ty', and a coercion, co_fn,
       -- which justifies the substitution.  If the coercion is not the identity
       -- then use transitivity with the original coercion
-      where
-        (co_fn, ty') = refineType (Reft in_scope fixpt) ty
-        co1 | WpCo co'' <- co_fn = mkTransCoercion co co''
-            | otherwise          = ASSERT( isIdHsWrapper co_fn ) co 
 
 -----------------------------
 fixTvSubstEnv :: InScopeSet -> TvSubstEnv -> TvSubstEnv
@@ -256,11 +256,7 @@ 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
@@ -273,6 +269,7 @@ badReftElts env
 		     | otherwise = False
 	where
 	  (ty1,ty2) = coercionKind co
+#endif
 
 emptyInternalReft :: InternalReft
 emptyInternalReft = emptyVarEnv
@@ -552,4 +549,4 @@ kindMisMatch tv1 t2
 occursCheck tv ty
   = hang (ptext SLIT("Can't construct the infinite type"))
        2 (ppr tv <+> equals <+> ppr ty)
-\end{code}
\ No newline at end of file
+\end{code}