{"ast_node_type":"variable","tokens":[{"end":70,"kind":"keyword","start":0,"text":"let"}]}
                    let default = type_param.default_type().map(|it| {
                    let name = type_param.name().map_or_else(Name::missing, |it| it.as_name());
                        ec.lower_type_ref(it, &mut ExprCollector::impl_trait_error_allocator)