error[E0658]: `impl Trait` in type aliases is unstable
  --> $DIR/drop_elaboration_with_errors2.rs:5:25
   |
LL |     pub type Alias<T> = impl Sized;
   |                         ^^^^^^^^^^
   |
   = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
   = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0119]: conflicting implementations of trait `Trait<_>`
  --> $DIR/drop_elaboration_with_errors2.rs:26:1
   |
LL | impl<T> Trait<T> for T {
   | ---------------------- first implementation here
...
LL | impl<T> Trait<T> for defining_scope::Alias<T> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation

error: unconstrained opaque type
  --> $DIR/drop_elaboration_with_errors2.rs:5:25
   |
LL |     pub type Alias<T> = impl Sized;
   |                         ^^^^^^^^^^
   |
   = note: `Alias` must be used in combination with a concrete type within the same crate

error[E0308]: mismatched types
  --> $DIR/drop_elaboration_with_errors2.rs:10:9
   |
LL |     pub type Alias<T> = impl Sized;
   |                         ---------- the found opaque type
...
LL |     pub fn cast<T>(x: Container<Alias<T>, T>) -> Container<T, T> {
   |                 - expected this type parameter   --------------- expected `Container<T, T>` because of return type
LL |         x
   |         ^ expected `Container<T, T>`, found `Container<Alias<T>, T>`
   |
   = note: expected struct `Container<T, _>`
              found struct `Container<Alias<T>, _>`
   = help: type parameters must be constrained to match other types
   = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0119, E0308, E0658.
For more information about an error, try `rustc --explain E0119`.