error[E0521]: borrowed data escapes outside of closure --> $DIR/regions-escape-unboxed-closure.rs:5:23 | LL | let mut x: Option<&isize> = None; | ----- `x` declared here, outside of the closure body LL | with_int(&mut |y| x = Some(y)); | - ^^^^^^^^^^^ `y` escapes the closure body here | | | `y` is a reference that is only valid in the closure body error: aborting due to previous error For more information about this error, try `rustc --explain E0521`.