Update generated code with added comments
diff --git a/src/gen/fold.rs b/src/gen/fold.rs
index c6fb1a3..60935a9 100644
--- a/src/gen/fold.rs
+++ b/src/gen/fold.rs
@@ -30,6 +30,8 @@
 /// See the [module documentation] for details.
 ///
 /// [module documentation]: index.html
+///
+/// *This trait is available if Syn is built with the `"fold"` feature.*
 pub trait Fold {
 # [ cfg ( any ( feature = "full" , feature = "derive" ) ) ]
 fn fold_abi(&mut self, i: Abi) -> Abi { fold_abi(self, i) }