pub struct CrateId { local_path: String, junk: String, } impl CrateId { fn new(s: &str) -> CrateId { CrateId { local_path: s.to_string(), junk: "wutevs".to_string() } } } pub fn remove_package_from_database() { let mut lines_to_use: Vec<&CrateId> = Vec::new(); //~^ NOTE `lines_to_use` declared here, outside of the closure body let push_id = |installed_id: &CrateId| { //~^ NOTE `installed_id` is a reference that is only valid in the closure body lines_to_use.push(installed_id); //~^ ERROR borrowed data escapes outside of closure //~| NOTE `installed_id` escapes the closure body here }; list_database(push_id); for l in &lines_to_use { println!("{}", l.local_path); } } pub fn list_database(mut f: F) where F: FnMut(&CrateId), { let stuff = ["foo", "bar"]; for l in &stuff { f(&CrateId::new(*l)); } } pub fn main() { remove_package_from_database(); }