error[E0507]: cannot move out of `*v`, as `v` is a 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)) | -- ^^ move occurs because `*v` has type `T`, which does not implement the `Copy` trait | | | captured by this `FnMut` closure error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0507`.