{"ast_node_type":"other","tokens":[{"end":35,"kind":"keyword","start":0,"text":"type"}]}
            type Extra = $extra_ty;
        impl<$vis_ty: MutVisitor> MutVisitable<$vis_ty> for $self_ty {
            fn visit_mut(&mut $self, $vis: &mut $vis_ty, $extra: Self::Extra) -> V::Result {