Implement simple effect typing for variables

src/zone.h

Index: src/zone.h
diff --git a/src/zone.h b/src/zone.h
index a12ed79312333b896277a1ec2067f505d4055b3c..a61099c6bf69c1f758b0fc4fbd2c16ad33e9f00b 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -177,6 +177,7 @@ struct ZoneAllocationPolicy {
   explicit ZoneAllocationPolicy(Zone* zone) : zone_(zone) { }
   INLINE(void* New(size_t size));
   INLINE(static void Delete(void *pointer)) { }
+  Zone* zone() { return zone_; }
 
  private:
   Zone* zone_;
@@ -246,6 +247,8 @@ class ZoneSplayTree: public SplayTree<Config, ZoneAllocationPolicy> {
   explicit ZoneSplayTree(Zone* zone)
       : SplayTree<Config, ZoneAllocationPolicy>(ZoneAllocationPolicy(zone)) {}
   ~ZoneSplayTree();
+
+  INLINE(void* operator new(size_t size, Zone* zone));
 };