warning: the feature `type_alias_impl_trait` is incomplete and may not be safe to use and/or cause compiler crashes
  --> $DIR/declared_but_not_defined_in_scope.rs:3:32
   |
LL | #![cfg_attr(full_tait, feature(type_alias_impl_trait))]
   |                                ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[warn(incomplete_features)]` on by default
   = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information

error: could not find defining uses
  --> $DIR/declared_but_not_defined_in_scope.rs:10:20
   |
LL |     pub type Boo = impl ::std::fmt::Debug;
   |                    ^^^^^^^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
  --> $DIR/declared_but_not_defined_in_scope.rs:14:5
   |
LL |     pub type Boo = impl ::std::fmt::Debug;
   |                    ---------------------- the expected opaque type
...
LL | fn bomp() -> boo::Boo {
   |              -------- expected `impl Debug` because of return type
LL |     ""
   |     ^^ expected opaque type, found `&str`
   |
   = note: expected opaque type `impl Debug`
                found reference `&'static str`

error: aborting due to 2 previous errors; 1 warning emitted

For more information about this error, try `rustc --explain E0308`.