#![feature(box_patterns)] fn arg_item(box ref x: Box) -> &'static isize { x //~ ERROR cannot return value referencing function parameter } fn with(f: F) -> R where F: FnOnce(Box) -> R { f(Box::new(3)) } fn arg_closure() -> &'static isize { with(|box ref x| x) //~ ERROR cannot return value referencing function parameter } fn main() {}