diff --git a/tasks/ast_codegen/src/schema.rs b/tasks/ast_codegen/src/schema.rs
index a4ff8d2a554a57..9054a7c7e02376 100644
--- a/tasks/ast_codegen/src/schema.rs
+++ b/tasks/ast_codegen/src/schema.rs
@@ -154,9 +154,15 @@ impl RType {
     }
 
     pub fn set_visitable(&mut self, value: bool) -> Result<()> {
+        macro_rules! assign {
+            ($it:ident) => {{
+                debug_assert!($it.meta.ast, "only ast types can be visitable!");
+                $it.meta.visitable = value;
+            }};
+        }
         match self {
-            RType::Enum(it) => it.meta.visitable = value,
-            RType::Struct(it) => it.meta.visitable = value,
+            RType::Enum(it) => assign!(it),
+            RType::Struct(it) => assign!(it),
             _ => return Err("Unsupported type!".to_string()),
         }
         Ok(())