error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
  --> $DIR/issue-87258_a.rs:19:21
   |
LL |     fn foo<'a>() -> Self::FooFuture<'a> {
   |                     ^^^^^^^^^^^^^^^^^^^
   |
   = note: hidden type `Struct<'_>` captures lifetime '_#7r

error: aborting due to previous error

For more information about this error, try `rustc --explain E0700`.