[project @ 1999-03-17 10:06:21 by simonpj]

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

diff --git a/ghc/compiler/typecheck/TcUnify.lhs b/ghc/compiler/typecheck/TcUnify.lhs
index 6fd0ba7..f7a78e5 100644 (file)
--- a/ghc/compiler/typecheck/TcUnify.lhs
+++ b/ghc/compiler/typecheck/TcUnify.lhs
@@ -24,7 +24,7 @@ import Type   ( Type(..), tyVarsOfType, funTyCon,
                )
 import TyCon   ( TyCon, isTupleTyCon, isUnboxedTupleTyCon, 
                  tyConArity )
-import Name    ( isSystemName )
+import Name    ( hasBetterProv )
 import Var     ( TyVar, tyVarKind, varName )
 import VarEnv  
 import VarSet  ( varSetElems )
@@ -272,8 +272,7 @@ uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2@(TyVarTy tv2)
        Nothing -> checkKinds swapped tv1 ty2                   `thenTc_`
 
                        -- Try to update sys-y type variables in preference to sig-y ones
-                       -- (the latter respond False to isSystemName)
-                  if isSystemName (varName tv2) then
+                  if varName tv1 `hasBetterProv` varName tv2 then
                        tcPutTyVar tv2 (TyVarTy tv1)                            `thenNF_Tc_`
                        returnTc ()
                   else