{"ast_node_type":"other","tokens":[{"end":53,"kind":"keyword","start":0,"text":"walk_flat_map_field_def(self,"}]}
                    walk_flat_map_field_def(self, fd)
                fn flat_map_field_def(&mut self, fd: FieldDef) -> SmallVec<[FieldDef; 1]> {
                }