Make recursion and RULES interact better

[ghc-hetmet.git] / compiler / main / TidyPgm.lhs

diff --git a/compiler/main/TidyPgm.lhs b/compiler/main/TidyPgm.lhs
index 4e01fd3..aee6743 100644 (file)
--- a/compiler/main/TidyPgm.lhs
+++ b/compiler/main/TidyPgm.lhs
@@ -451,9 +451,10 @@ addExternal (id,rhs) needed
   = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
                 id show_unfold
   where
-    add_occ id needed = extendVarEnv needed id False
+    add_occ id needed | id `elemVarEnv` needed = needed
+                     | otherwise              = extendVarEnv needed id False
        -- "False" because we don't know we need the Id's unfolding
-       -- We'll override it later when we find the binding site
+       -- Don't override existing bindings; we might have already set it to True
 
     new_needed_ids = worker_ids        `unionVarSet`
                     unfold_ids `unionVarSet`