error[E0433]: failed to resolve: `Self` is only available in impls, traits, and type definitions
  --> $DIR/unreachable-issue-121455.rs:1:13
   |
LL | fn test(s: &Self::Id) {
   |             ^^^^ `Self` is only available in impls, traits, and type definitions

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0433`.