warning: impl trait in impl method signature does not match trait method signature
  --> $DIR/async-example-desugared-manual.rs:22:22
   |
LL |     async fn foo(&self) -> i32;
   |     --------------------------- return type from trait method defined here
...
LL |     fn foo(&self) -> MyFuture {
   |                      ^^^^^^^^
   |
   = note: add `#[allow(refining_impl_trait)]` if it is intended for this to be part of the public API of this crate
   = note: we are soliciting feedback, see issue #121718 <https://github.com/rust-lang/rust/issues/121718> for more information
note: the lint level is defined here
  --> $DIR/async-example-desugared-manual.rs:21:12
   |
LL |     #[warn(refining_impl_trait)]
   |            ^^^^^^^^^^^^^^^^^^^
   = note: `#[warn(refining_impl_trait_reachable)]` implied by `#[warn(refining_impl_trait)]`
help: replace the return type so that it matches the trait
   |
LL |     fn foo(&self) -> impl Future<Output = i32> {
   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~

warning: 1 warning emitted