error[E0038]: the trait `Baz` cannot be made into an object
  --> $DIR/object-safety-supertrait-mentions-Self.rs:16:31
   |
LL | fn make_baz<T:Baz>(t: &T) -> &dyn Baz {
   |                               ^^^^^^^ `Baz` cannot be made into an object
   |
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
  --> $DIR/object-safety-supertrait-mentions-Self.rs:8:13
   |
LL | trait Baz : Bar<Self> {
   |       ---   ^^^^^^^^^ ...because it uses `Self` as a type parameter
   |       |
   |       this trait cannot be made into an object...
help: consider using an opaque type instead
   |
LL | fn make_baz<T:Baz>(t: &T) -> &impl Baz {
   |                               ~~~~

error[E0277]: the size for values of type `Self` cannot be known at compilation time
  --> $DIR/object-safety-supertrait-mentions-Self.rs:8:13
   |
LL | trait Baz : Bar<Self> {
   |             ^^^^^^^^^ doesn't have a size known at compile-time
   |
note: required by a bound in `Bar`
  --> $DIR/object-safety-supertrait-mentions-Self.rs:4:11
   |
LL | trait Bar<T> {
   |           ^ required by this bound in `Bar`
help: consider further restricting `Self`
   |
LL | trait Baz : Bar<Self> + Sized {
   |                       +++++++
help: consider relaxing the implicit `Sized` restriction
   |
LL | trait Bar<T: ?Sized> {
   |            ++++++++

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0038, E0277.
For more information about an error, try `rustc --explain E0038`.