error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
  --> $DIR/try-on-option-diagnostics.rs:7:5
   |
LL | / fn a_function() -> u32 {
LL | |     let x: Option<u32> = None;
LL | |     x?;
   | |     ^^ cannot use the `?` operator in a function that returns `u32`
LL | |     22
LL | | }
   | |_- this function should return `Result` or `Option` to accept `?`
   |
   = help: the trait `std::ops::Try` is not implemented for `u32`
   = note: required by `std::ops::Try::from_error`

error[E0277]: the `?` operator can only be used in a closure that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
  --> $DIR/try-on-option-diagnostics.rs:14:9
   |
LL |       let a_closure = || {
   |  _____________________-
LL | |         let x: Option<u32> = None;
LL | |         x?;
   | |         ^^ cannot use the `?` operator in a closure that returns `{integer}`
LL | |         22
LL | |     };
   | |_____- this function should return `Result` or `Option` to accept `?`
   |
   = help: the trait `std::ops::Try` is not implemented for `{integer}`
   = note: required by `std::ops::Try::from_error`

error[E0277]: the `?` operator can only be used in a method that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
  --> $DIR/try-on-option-diagnostics.rs:26:13
   |
LL | /         fn a_method() {
LL | |             let x: Option<u32> = None;
LL | |             x?;
   | |             ^^ cannot use the `?` operator in a method that returns `()`
LL | |         }
   | |_________- this function should return `Result` or `Option` to accept `?`
   |
   = help: the trait `std::ops::Try` is not implemented for `()`
   = note: required by `std::ops::Try::from_error`

error[E0277]: the `?` operator can only be used in a trait method that returns `Result` or `Option` (or another type that implements `std::ops::Try`)
  --> $DIR/try-on-option-diagnostics.rs:39:13
   |
LL | /         fn a_trait_method() {
LL | |             let x: Option<u32> = None;
LL | |             x?;
   | |             ^^ cannot use the `?` operator in a trait method that returns `()`
LL | |         }
   | |_________- this function should return `Result` or `Option` to accept `?`
   |
   = help: the trait `std::ops::Try` is not implemented for `()`
   = note: required by `std::ops::Try::from_error`

error: aborting due to 4 previous errors

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