error: item does not constrain `Foo::{opaque#0}`, but has it in its signature
  --> $DIR/issue-70877.rs:30:12
   |
LL |     pub fn oof(_: Foo) -> impl std::fmt::Debug {
   |            ^^^
   |
   = note: consider moving the opaque type's declaration and defining uses into a separate module
note: this opaque type is in the signature
  --> $DIR/issue-70877.rs:26:20
   |
LL |     pub type Foo = impl Iterator<Item = super::FooItem>;
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error