1error[E0594]: cannot assign to `counter`, as it is a captured variable in a `Fn` closure
2  --> $DIR/unboxed-closures-mutated-upvar-from-fn-closure.rs:11:9
3   |
4LL |   fn call<F>(f: F) where F : Fn() {
5   |                 - change this to accept `FnMut` instead of `Fn`
6...
7LL |       call(|| {
8   |  _____----_-
9   | |     |
10   | |     expects `Fn` instead of `FnMut`
11LL | |         counter += 1;
12   | |         ^^^^^^^^^^^^ cannot assign
13LL | |
14LL | |     });
15   | |_____- in this closure
16
17error: aborting due to previous error
18
19For more information about this error, try `rustc --explain E0594`.
20