error[E0220]: associated type `Proj` not found for `Family<Option<()>>` in the current scope
  --> $DIR/not-found-self-type-differs.rs:17:34
   |
LL | struct Family<T>(T);
   | ---------------- associated item `Proj` not found for this struct
...
LL | type Alias = Family<Option<()>>::Proj;
   |                                  ^^^^ associated item not found in `Family<Option<()>>`
   |
   = note: the associated type was found for
           - `Family<()>`
           - `Family<Result<T, ()>>`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0220`.