error[E0277]: the `?` operator can only be used on `Result`s, not `Option`s, in a function that returns `Result`
  --> $DIR/try-on-option.rs:5:6
   |
LL | fn foo() -> Result<u32, ()> {
   | --------------------------- this function returns a `Result`
LL |     let x: Option<u32> = None;
LL |     x?;
   |      ^ use `.ok_or(...)?` to provide an error compatible with `Result<u32, ()>`
   |
   = help: the trait `FromResidual<Option<Infallible>>` is not implemented for `Result<u32, ()>`
   = help: the trait `FromResidual<Result<Infallible, E>>` is implemented for `Result<T, F>`

error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
  --> $DIR/try-on-option.rs:11:6
   |
LL | fn bar() -> u32 {
   | --------------- this function should return `Result` or `Option` to accept `?`
LL |     let x: Option<u32> = None;
LL |     x?;
   |      ^ cannot use the `?` operator in a function that returns `u32`
   |
   = help: the trait `FromResidual<Option<Infallible>>` is not implemented for `u32`

error: aborting due to 2 previous errors

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