AstBuilder: generate with mutability

src/main.rs

@@ -20,7 +20,9 @@ struct Args {
 fn main() {
     let args = Args::parse();
     let params = Params::parse(&args.config);
-    let builder = AstBuilder::from(params);
+    let mut builder = AstBuilder::from(params);
+
+    builder.generate();
 
     println!("{}", builder.to_string());
 }