warning: this `Deref` implementation is covered by an implicit supertrait coercion
  --> $DIR/deref-lint-regions.rs:8:1
   |
LL | impl<'a> Deref for dyn Foo<'a> {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn Foo<'_>` implements `Deref<Target = dyn Bar<'_>>` which conflicts with supertrait `Bar<'_>`
LL |
LL |     type Target = dyn Bar<'a>;
   |     -------------------------- target type is a supertrait of `dyn Foo<'_>`
   |
   = help: consider removing this implementation or replacing it with a method instead
   = note: `#[warn(deref_into_dyn_supertrait)]` on by default

warning: 1 warning emitted