Implement simple effect typing for variables

src/types.h

Index: src/types.h
diff --git a/src/types.h b/src/types.h
index b2eb60c69203b990a575346ab7eb41a3001405c0..fc69c785295a23b6ca976ab91c15b9a8a43a58f2 100644
--- a/src/types.h
+++ b/src/types.h
@@ -303,6 +303,11 @@ struct Bounds {
   explicit Bounds(Handle<Type> t) : lower(t), upper(t) {}
   Bounds(Type* t, Isolate* isl) : lower(t, isl), upper(t, isl) {}
 
+  // Unrestricted bounds.
+  static Bounds Unbounded(Isolate* isl) {
+    return Bounds(Type::None(), Type::Any(), isl);
+  }
+
   // Meet: both b1 and b2 are known to hold.
   static Bounds Both(Bounds b1, Bounds b2, Isolate* isl) {
     return Bounds(