warning: use the `?` operator instead of an `and_then` call
  --> src/main.rs:11:38
   |
11 |         } else if let Some(parent) = b.and_then(|p| p.parent()) {
   |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#return_and_then
note: the lint level is defined here
  --> src/main.rs:1:9
   |
1  | #![warn(clippy::return_and_then)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^
help: try
   |
11 ~         } else if let Some(parent) = {
12 +             let p = b?;
13 +             p.parent()
14 ~         } {
   |

error[E0277]: the `?` operator can only be used in a closure that returns `Result` or `Option` (or another type that implements `FromResidual`)
  --> src/main.rs:12:22
   |
8  |     func: |check, a, b| {
   |           ------------- this function should return `Result` or `Option` to accept `?`
...
12 |             let p = b?;
   |                      ^ cannot use the `?` operator in a closure that returns `()`

For more information about this error, try `rustc --explain E0277`.