error[E0119]: conflicting implementations of trait `Trait<_>`
  --> $DIR/opaques.rs:30:1
   |
LL | impl<T> Trait<T> for T {
   | ---------------------- first implementation here
...
LL | impl<T> Trait<T> for defining_scope::Alias<T> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation

error[E0282]: type annotations needed
  --> $DIR/opaques.rs:13:20
   |
LL |     pub fn cast<T>(x: Container<Alias<T>, T>) -> Container<T, T> {
   |                    ^ cannot infer type for associated type `<T as Trait<T>>::Assoc`

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0119, E0282.
For more information about an error, try `rustc --explain E0119`.