X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FUnify.lhs;h=7c8ad9dbb2f4b4db4d7c9ab49d4f8e24c234847e;hb=a385f0af5ea320a18d580f6a36c59c55b3516efd;hp=9137150cc3fe84164c905a38fcc2ce320fb288ae;hpb=3d5970436af5ab73957278671059e00d1a52c616;p=ghc-hetmet.git

diff --git a/compiler/types/Unify.lhs b/compiler/types/Unify.lhs
index 9137150..7c8ad9d 100644
--- a/compiler/types/Unify.lhs
+++ b/compiler/types/Unify.lhs
@@ -158,23 +158,19 @@ match menv subst ty1 ty2 | Just ty1' <- coreView ty1 = match menv subst ty1' ty2
 			 | Just ty2' <- coreView ty2 = match menv subst ty1 ty2'
 
 match menv subst (TyVarTy tv1) ty2
+  | Just ty1' <- lookupVarEnv subst tv1'	-- tv1' is already bound
+  = if tcEqTypeX (nukeRnEnvL rn_env) ty1' ty2
+	-- ty1 has no locally-bound variables, hence nukeRnEnvL
+	-- Note tcEqType...we are doing source-type matching here
+    then Just subst
+    else Nothing	-- ty2 doesn't match
+
   | tv1' `elemVarSet` me_tmpls menv
-  = case lookupVarEnv subst tv1' of
-	Nothing 	-- No existing binding
-	    | any (inRnEnvR rn_env) (varSetElems (tyVarsOfType ty2))
-	    -> Nothing	-- Occurs check
-	    | otherwise	
-	    -> do { subst1 <- match_kind menv subst tv1 ty2
-		  ; return (extendVarEnv subst1 tv1' ty2) }
+  = if any (inRnEnvR rn_env) (varSetElems (tyVarsOfType ty2))
+    then Nothing	-- Occurs check
+    else do { subst1 <- match_kind menv subst tv1 ty2
 			-- Note [Matching kinds]
-
-	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
-	    | otherwise	-> Nothing	-- ty2 doesn't match
-	    
+	    ; return (extendVarEnv subst1 tv1' ty2) }
 
    | otherwise	-- tv1 is not a template tyvar
    = case ty2 of
@@ -393,7 +389,7 @@ type InternalReft = TyVarEnv (Coercion, Type)
 
 instance Outputable Refinement where
   ppr (Reft _in_scope env)
-    = ptext SLIT("Refinement") <+>
+    = ptext (sLit "Refinement") <+>
         braces (ppr env)
 
 emptyRefinement :: Refinement
@@ -771,23 +767,23 @@ maybeErrToMaybe (Failed _)    = Nothing
 \begin{code}
 misMatch :: Type -> Type -> SDoc
 misMatch t1 t2
-  = ptext SLIT("Can't match types") <+> quotes (ppr t1) <+> 
-    ptext SLIT("and") <+> quotes (ppr t2)
+  = ptext (sLit "Can't match types") <+> quotes (ppr t1) <+> 
+    ptext (sLit "and") <+> quotes (ppr t2)
 
 lengthMisMatch :: [Type] -> [Type] -> SDoc
 lengthMisMatch tys1 tys2
-  = sep [ptext SLIT("Can't match unequal length lists"), 
+  = sep [ptext (sLit "Can't match unequal length lists"), 
 	 nest 2 (ppr tys1), nest 2 (ppr tys2) ]
 
 kindMisMatch :: TyVar -> Type -> SDoc
 kindMisMatch tv1 t2
-  = vcat [ptext SLIT("Can't match kinds") <+> quotes (ppr (tyVarKind tv1)) <+> 
-	    ptext SLIT("and") <+> quotes (ppr (typeKind t2)),
-	  ptext SLIT("when matching") <+> quotes (ppr tv1) <+> 
-		ptext SLIT("with") <+> quotes (ppr t2)]
+  = vcat [ptext (sLit "Can't match kinds") <+> quotes (ppr (tyVarKind tv1)) <+> 
+	    ptext (sLit "and") <+> quotes (ppr (typeKind t2)),
+	  ptext (sLit "when matching") <+> quotes (ppr tv1) <+> 
+		ptext (sLit "with") <+> quotes (ppr t2)]
 
 occursCheck :: TyVar -> Type -> SDoc
 occursCheck tv ty
-  = hang (ptext SLIT("Can't construct the infinite type"))
+  = hang (ptext (sLit "Can't construct the infinite type"))
        2 (ppr tv <+> equals <+> ppr ty)
 \end{code}