X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FUnify.lhs;h=f99c56c0d4f1fcb1d45093cb5fc5294c6e29fb32;hb=ff8e1d01524b48e028b09e2b04b2e5303cb6d95f;hp=9f5b405415f5d0e9235a53f60c8bcb9e9d532861;hpb=c76c69c5b62f1ca4fa52d75b0dfbd37b7eddbb09;p=ghc-hetmet.git

diff --git a/compiler/types/Unify.lhs b/compiler/types/Unify.lhs
index 9f5b405..f99c56c 100644
--- a/compiler/types/Unify.lhs
+++ b/compiler/types/Unify.lhs
@@ -1,23 +1,23 @@
+%
+% (c) The University of Glasgow 2006
+%
+
 \begin{code}
 module Unify ( 
 	-- Matching of types: 
 	--	the "tc" prefix indicates that matching always
 	--	respects newtypes (rather than looking through them)
-	tcMatchTys, tcMatchTyX, ruleMatchTyX, tcMatchPreds, MatchEnv(..)
+	tcMatchTy, tcMatchTys, tcMatchTyX, 
+	ruleMatchTyX, tcMatchPreds, MatchEnv(..)
    ) where
 
 #include "HsVersions.h"
 
-import Var		( Var, TyVar, tyVarKind )
+import Var
 import VarEnv
 import VarSet
-import Type		( typeKind, tyVarsOfType, tyVarsOfTypes, tyVarsOfTheta, mkTyVarTys,
-			  TvSubstEnv, emptyTvSubstEnv, TvSubst(..), substTy, tcEqTypeX,
-			  mkOpenTvSubst, tcView, isSubKind, eqKind, repSplitAppTy_maybe )
-import TypeRep          ( Type(..), PredType(..), funTyCon )
-import DataCon 		( DataCon, dataConResTys )
-import Util		( snocView )
-import ErrUtils		( Message )
+import Type
+import TypeRep
 import Outputable
 import Maybes
 \end{code}
@@ -58,10 +58,26 @@ data MatchEnv
  	, me_env   :: RnEnv2	-- Renaming envt for nested foralls
 	}			--   In-scope set includes template tyvars
 
+tcMatchTy :: TyVarSet		-- Template tyvars
+	  -> Type		-- Template
+	  -> Type		-- Target
+	  -> Maybe TvSubst	-- One-shot; in principle the template
+				-- variables could be free in the target
+
+tcMatchTy tmpls ty1 ty2
+  = case match menv emptyTvSubstEnv ty1 ty2 of
+	Just subst_env -> Just (TvSubst in_scope subst_env)
+	Nothing	       -> Nothing
+  where
+    menv     = ME { me_tmpls = tmpls, me_env = mkRnEnv2 in_scope }
+    in_scope = mkInScopeSet (tmpls `unionVarSet` tyVarsOfType ty2)
+	-- We're assuming that all the interesting 
+	-- tyvars in tys1 are in tmpls
+
 tcMatchTys :: TyVarSet		-- Template tyvars
-	 -> [Type]		-- Template
-	 -> [Type]		-- Target
-	 -> Maybe TvSubst	-- One-shot; in principle the template
+	   -> [Type]		-- Template
+	   -> [Type]		-- Target
+	   -> Maybe TvSubst	-- One-shot; in principle the template
 				-- variables could be free in the target
 
 tcMatchTys tmpls tys1 tys2
@@ -121,24 +137,26 @@ match :: MatchEnv	-- For the most part this is pushed downwards
 -- it respects NewTypes and PredType
 
 match menv subst ty1 ty2 | Just ty1' <- tcView ty1 = match menv subst ty1' ty2
-match menv subst ty1 ty2 | Just ty2' <- tcView ty2 = match menv subst ty1 ty2'
+			  | Just ty2' <- tcView ty2 = match menv subst ty1 ty2'
 
 match menv subst (TyVarTy tv1) ty2
-  | tv1 `elemVarSet` me_tmpls menv
+  | tv1' `elemVarSet` me_tmpls menv
   = case lookupVarEnv subst tv1' of
-	Nothing | any (inRnEnvR rn_env) (varSetElems (tyVarsOfType ty2))
-		-> Nothing	-- Occurs check
-		| not (typeKind ty2 `isSubKind` tyVarKind tv1)
-		-> Nothing	-- Kind mis-match
-		| otherwise
-		-> Just (extendVarEnv subst tv1 ty2)
-
-	Just ty1' | tcEqTypeX (nukeRnEnvL rn_env) ty1' ty2
+	Nothing 	-- No existing binding
+	    | any (inRnEnvR rn_env) (varSetElems (tyVarsOfType ty2))
+	    -> Nothing	-- Occurs check
+	    | not (typeKind ty2 `isSubKind` tyVarKind tv1)
+	    -> Nothing	-- Kind mis-match
+	    | otherwise
+	    -> Just (extendVarEnv subst tv1' ty2)
+
+	Just ty1' 	-- There is an existing binding; check whether ty2 matches it
+	    | tcEqTypeX (nukeRnEnvL rn_env) ty1' ty2
 		-- ty1 has no locally-bound variables, hence nukeRnEnvL
 		-- Note tcEqType...we are doing source-type matching here
-		  -> Just subst
-
-	other -> Nothing
+	    -> Just subst
+	    | otherwise	-> Nothing	-- ty2 doesn't match
+	    
 
    | otherwise	-- tv1 is not a template tyvar
    = case ty2 of
@@ -162,6 +180,7 @@ match menv subst (FunTy ty1a ty1b) (FunTy ty2a ty2b)
        ; match menv subst' ty1b ty2b }
 match menv subst (AppTy ty1a ty1b) ty2
   | Just (ty2a, ty2b) <- repSplitAppTy_maybe ty2
+	-- 'repSplit' used because the tcView stuff is done above
   = do { subst' <- match menv subst ty1a ty2a
        ; match menv subst' ty1b ty2b }