Visitor trait `visit_arg` is never called

[jvllmr]

When using the Visitor trait I realized that the default values of arguments are never visited. This is because the visit_arg function is never actuall called:

Parser/ast/src/gen/visitor.rs

Line 737 in 4588ea5

fn visit_arg(&mut self, node: Arg<R>) {

I also could not see an implementation for visiting the default value of an arg.