error[E0321]: traits with a default impl, like `Trait`, cannot be implemented for type alias `Alias`
  --> $DIR/impl_for_weak_alias.rs:7:1
   |
LL | impl Trait for Alias {}
   | ^^^^^^^^^^^^^^^^^^^^
   |
   = note: a trait object implements `Trait` if and only if `Trait` is one of the trait object's trait bounds

error: aborting due to previous error

For more information about this error, try `rustc --explain E0321`.