:art: remove warnings in ast

diff --git a/ast b/ast
index 6ffab44c6801d98fc81700927a47471ea607a73d..b940c8d513654ebf3902b4e4d10e6acf6124e08d 160000 (submodule)
--- a/ast
+++ b/ast
@@ -1 +1 @@
-Subproject commit 6ffab44c6801d98fc81700927a47471ea607a73d
+Subproject commit b940c8d513654ebf3902b4e4d10e6acf6124e08d