Fix a nasty bug in RULE matching: Trac #4814

[ghc-hetmet.git] / compiler / basicTypes / VarEnv.lhs

diff --git a/compiler/basicTypes/VarEnv.lhs b/compiler/basicTypes/VarEnv.lhs
index cd6f031..f275714 100644 (file)
--- a/compiler/basicTypes/VarEnv.lhs
+++ b/compiler/basicTypes/VarEnv.lhs
@@ -36,7 +36,8 @@ module VarEnv (
        
        -- ** Operations on RnEnv2s
        mkRnEnv2, rnBndr2, rnBndrs2, rnOccL, rnOccR, inRnEnvL, inRnEnvR,
-       rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR, extendRnInScopeList,
+        rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR,
+        addRnInScopeSet,
         rnEtaL, rnEtaR,
        rnInScope, rnInScopeSet, lookupRnInScope,
 
@@ -204,9 +205,10 @@ mkRnEnv2 vars = RV2        { envL     = emptyVarEnv
                        , envR     = emptyVarEnv
                        , in_scope = vars }
 
-extendRnInScopeList :: RnEnv2 -> [Var] -> RnEnv2
-extendRnInScopeList env vs
-  = env { in_scope = extendInScopeSetList (in_scope env) vs }
+addRnInScopeSet :: RnEnv2 -> VarEnv Var -> RnEnv2
+addRnInScopeSet env vs
+  | isEmptyVarEnv vs = env
+  | otherwise        = env { in_scope = extendInScopeSetSet (in_scope env) vs }
 
 rnInScope :: Var -> RnEnv2 -> Bool
 rnInScope x env = x `elemInScopeSet` in_scope env