error[E0277]: the trait bound `DefaultAllocator: Allocator` is not satisfied
  --> $DIR/wf-packed-on-proj-of-type-as-unimpl-trait.rs:28:12
   |
LL | struct Foo(Matrix<<DefaultAllocator as Allocator>::Buffer>);
   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Allocator` is not implemented for `DefaultAllocator`
   |
help: this trait has no implementations, consider adding one
  --> $DIR/wf-packed-on-proj-of-type-as-unimpl-trait.rs:23:1
   |
LL | pub trait Allocator { type Buffer; }
   | ^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.