diff --git a/tools/genast.py b/tools/genast.py
index e4d6bf9..27cc726 100755
--- a/tools/genast.py
+++ b/tools/genast.py
@@ -53,7 +53,7 @@ def define_visitor(wr: FileWriter, base: str, type_lines: list[str]):
 
     for type, members in types:
         wr.line(
-            f"    fn visit_{type.lower()}_{base.lower()}(&mut self, {base.lower()}: &{type}{base});"
+            f"    fn visit_{type.lower()}_{base.lower()}(&mut self, {base.lower()}: &{type}{base}) -> Result<(), Box<dyn std::error::Error>>;"
         )
     wr.line("}")
     wr.line()
@@ -69,7 +69,9 @@ def define_ast(wr: FileWriter, base: str, type_lines: list[str]):
     visitor = f"{base}Visitor"
 
     wr.line(f"pub trait {base}: Debug + Any " + "{")
-    wr.line(f"    fn accept(&self, visitor: &mut dyn {visitor});")
+    wr.line(
+        f"    fn accept(&self, visitor: &mut dyn {visitor}) -> Result<(), Box<dyn std::error::Error>>;"
+    )
     wr.line("    fn as_any(self: Box<Self>) -> Box<dyn Any>;")
     wr.line("    fn as_any_ref(&self) -> &dyn Any;")
     wr.line("}")
@@ -85,8 +87,11 @@ def define_ast(wr: FileWriter, base: str, type_lines: list[str]):
         wr.line("}")
         wr.line()
         wr.line(f"impl {base} for {type}{base} " + "{")
-        wr.line(f"    fn accept(&self, visitor: &mut dyn {visitor})" + "{")
-        wr.line(f"        visitor.visit_{type.lower()}_{base.lower()}(self);")
+        wr.line(
+            f"    fn accept(&self, visitor: &mut dyn {visitor}) -> Result<(), Box<dyn std::error::Error>>"
+            + "{"
+        )
+        wr.line(f"        visitor.visit_{type.lower()}_{base.lower()}(self)")
         wr.line("    }")
         wr.line()
         wr.line("    fn as_any(self: Box<Self>) -> Box<dyn Any> {")
@@ -111,10 +116,12 @@ def main():
 
     wr = FileWriter(path)
 
+    # File headers
     wr.line(
         "// This is an auto-generated file. Any changes made to this file may be overwritten."
     )
     wr.line("// This file was created at: " + time.strftime("%Y-%m-%d %H:%M:%S"))
+    wr.line("#![allow(dead_code)]")
 
     # Imports
     wr.line("use std::fmt::Debug;")