LL | inner(x)
| ^^^^^^^^ expected trait `std::iter::Iterator<Item = ()>`, found trait `std::iter::Iterator<Item = ()> + std::marker::Send`
|
- = note: expected type `std::option::Option<&dyn std::iter::Iterator<Item = ()>>`
- found type `std::option::Option<&dyn std::iter::Iterator<Item = ()> + std::marker::Send>`
+ = note: expected enum `std::option::Option<&dyn std::iter::Iterator<Item = ()>>`
+ found enum `std::option::Option<&dyn std::iter::Iterator<Item = ()> + std::marker::Send>`
error: aborting due to previous error