1 // Test that a by-ref `FnMut` closure gets an error when it tries to
2 // mutate a value.
3
call<F>(f: F) where F : Fn()4 fn call<F>(f: F) where F : Fn() {
5 f();
6 }
7
main()8 fn main() {
9 let mut counter = 0;
10 call(|| {
11 counter += 1;
12 //~^ ERROR cannot assign to `counter`
13 });
14 }
15