1 files changed, 7 insertions, 1 deletions
diff --git a/typesystem.h b/typesystem.h
index 5b0e7ca7b..bd99fd6c6 100644
--- a/typesystem.h
+++ b/typesystem.h
@@ -109,7 +109,13 @@ struct ArgumentOwner
         Add         = 0x01,
         Remove      = 0x02
     };
-    ArgumentOwner() : action(ArgumentOwner::Invalid), index(-2) {}
+    enum {
+        InvalidIndex = -2,
+        ThisIndex = -1,
+        ReturnIndex = 0,
+        FirstArgumentIndex = 1
+    };
+    ArgumentOwner() : action(ArgumentOwner::Invalid), index(ArgumentOwner::InvalidIndex) {}
 
     Action action;
     int index;