Document what feature everything requires
diff --git a/codegen/src/main.rs b/codegen/src/main.rs
index ac674a0..7f24774 100644
--- a/codegen/src/main.rs
+++ b/codegen/src/main.rs
@@ -1026,6 +1026,8 @@
/// 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 {{
{fold_trait}
}}
@@ -1086,6 +1088,8 @@
/// See the [module documentation] for details.
///
/// [module documentation]: index.html
+///
+/// *This trait is available if Syn is built with the `\"visit\"` feature.*
pub trait Visit<'ast> {{
{visit_trait}
}}
@@ -1122,6 +1126,8 @@
/// See the [module documentation] for details.
///
/// [module documentation]: index.html
+///
+/// *This trait is available if Syn is built with the `\"visit-mut\"` feature.*
pub trait VisitMut {{
{visit_mut_trait}
}}