warning: this `Deref` implementation is covered by an implicit supertrait coercion
  --> $DIR/migrate-lint-different-substs.rs:11:1
   |
LL | impl<'a> Deref for dyn Foo + 'a {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn Foo` implements `Deref<Target = dyn Bar<u32>>` which conflicts with supertrait `Bar<i32>`
...
LL |     type Target = dyn Bar<u32> + 'a;
   |     -------------------------------- target type is a supertrait of `dyn Foo`
   |
   = warning: this will change its meaning in a future release!
   = note: for more information, see issue #89460 <https://github.com/rust-lang/rust/issues/89460>
   = note: `#[warn(deref_into_dyn_supertrait)]` on by default

warning: 1 warning emitted