error: bound modifier `?` can only be applied to `Sized`
  --> $DIR/opt-out-bound-not-satisfied.rs:5:18
   |
LL | fn foo() -> impl ?Future<Output = impl Send> {
   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: bound modifier `?` can only be applied to `Sized`
  --> $DIR/opt-out-bound-not-satisfied.rs:5:18
   |
LL | fn foo() -> impl ?Future<Output = impl Send> {
   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: aborting due to 2 previous errors