1 // run-rustfix 2 3 // Point at the captured immutable outer variable 4 foo(mut f: Box<dyn FnMut()>)5fn foo(mut f: Box<dyn FnMut()>) { 6 f(); 7 } 8 main()9fn main() { 10 let y = true; 11 foo(Box::new(move || y = !y) as Box<_>); 12 //~^ ERROR cannot assign to `y`, as it is not declared as mutable 13 } 14