error[E0507]: cannot move out of captured variable in an `FnMut` closure --> $DIR/issue-4335.rs:6:20 | LL | fn f<'r, T>(v: &'r T) -> Box T + 'r> { | - captured outer variable LL | id(Box::new(|| *v)) | ^^ cannot move out of captured variable in an `FnMut` closure error[E0373]: closure may outlive the current function, but it borrows `v`, which is owned by the current function --> $DIR/issue-4335.rs:6:17 | LL | id(Box::new(|| *v)) | ^^ - `v` is borrowed here | | | may outlive borrowed value `v` | note: closure is returned here --> $DIR/issue-4335.rs:6:5 | LL | id(Box::new(|| *v)) | ^^^^^^^^^^^^^^^^^^^ help: to force the closure to take ownership of `v` (and any other referenced variables), use the `move` keyword | LL | id(Box::new(move || *v)) | ^^^^^^^ error: aborting due to 2 previous errors Some errors occurred: E0373, E0507. For more information about an error, try `rustc --explain E0373`.