1error[E0277]: expected a `Fn<()>` closure, found `extern "C" fn() {f}`
2  --> $DIR/extern-wrong-value-type.rs:9:11
3   |
4LL |     is_fn(f);
5   |     ----- ^ expected an `Fn<()>` closure, found `extern "C" fn() {f}`
6   |     |
7   |     required by a bound introduced by this call
8   |
9   = help: the trait `Fn<()>` is not implemented for `extern "C" fn() {f}`
10   = note: wrap the `extern "C" fn() {f}` in a closure with no arguments: `|| { /* code */ }`
11note: required by a bound in `is_fn`
12  --> $DIR/extern-wrong-value-type.rs:4:28
13   |
14LL | fn is_fn<F>(_: F) where F: Fn() {}
15   |                            ^^^^ required by this bound in `is_fn`
16
17error: aborting due to previous error
18
19For more information about this error, try `rustc --explain E0277`.
20