[project @ 2000-10-17 13:22:10 by simonmar]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcUnify.lhs

diff --git a/ghc/compiler/typecheck/TcUnify.lhs b/ghc/compiler/typecheck/TcUnify.lhs
index a026827..aa0a869 100644 (file)
--- a/ghc/compiler/typecheck/TcUnify.lhs
+++ b/ghc/compiler/typecheck/TcUnify.lhs
@@ -17,20 +17,20 @@ module TcUnify ( unifyTauTy, unifyTauTyList, unifyTauTyLists,
 -- friends: 
 import TcMonad
 import TypeRep ( Type(..), PredType(..) )  -- friend
-import Type    ( funTyCon, Kind, unboxedTypeKind, boxedTypeKind, openTypeKind, 
-                 superBoxity, typeCon, openKindCon, hasMoreBoxityInfo, 
+import Type    ( unboxedTypeKind, boxedTypeKind, openTypeKind, 
+                 typeCon, openKindCon, hasMoreBoxityInfo, 
                  tyVarsOfType, typeKind,
-                 mkTyVarTy, mkFunTy, splitFunTy_maybe, splitTyConApp_maybe,
+                 mkFunTy, splitFunTy_maybe, splitTyConApp_maybe,
                   isNotUsgTy, splitAppTy_maybe, mkTyConApp, 
                  tidyOpenType, tidyOpenTypes, tidyTyVar
                )
 import TyCon   ( TyCon, isTupleTyCon, tupleTyConBoxity, tyConArity )
-import Name    ( hasBetterProv )
-import Var     ( TyVar, tyVarKind, varName, isSigTyVar )
+import Var     ( tyVarKind, varName, isSigTyVar )
 import VarSet  ( varSetElems )
 import TcType  ( TcType, TcTauType, TcTyVar, TcKind, newBoxityVar,
                  newTyVarTy, newTyVarTys, tcGetTyVar, tcPutTyVar, zonkTcType
                )
+import Name    ( isSystemName )
 
 -- others:
 import BasicTypes ( Arity, Boxity, isBoxed )
@@ -316,7 +316,7 @@ uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2@(TyVarTy tv2)
                                -- Don't unify a signature type variable if poss
                        || k2 == openTypeKind
                                -- Try to get rid of open type variables as soon as poss
-                       || varName tv1 `hasBetterProv` varName tv2 
+                       || isSystemName (varName tv2)
                                -- Try to update sys-y type variables in preference to sig-y ones
 
        -- Second one isn't a type variable