| `impl Trait` is not allowed in path parameters. | |
| Erroneous code example: | |
| ```compile_fail,E0667 | |
| fn some_fn(mut x: impl Iterator) -> <impl Iterator>::Item { // error! | |
| x.next().unwrap() | |
| } | |
| ``` | |
| You cannot use `impl Trait` in path parameters. If you want something | |
| equivalent, you can do this instead: | |
| ``` | |
| fn some_fn<T: Iterator>(mut x: T) -> T::Item { // ok! | |
| x.next().unwrap() | |
| } | |
| ``` |