error[E0277]: `impl Future<Output = ()>` cannot be sent between threads safely
  --> $DIR/send-on-async-fn-in-trait.rs:13:16
   |
LL |     needs_send(T::test());
   |     ---------- ^^^^^^^^^ `impl Future<Output = ()>` cannot be sent between threads safely
   |     |
   |     required by a bound introduced by this call
   |
   = help: the trait `Send` is not implemented for `impl Future<Output = ()>`
note: required by a bound in `needs_send`
  --> $DIR/send-on-async-fn-in-trait.rs:12:27
   |
LL |     fn needs_send(_: impl Send) {}
   |                           ^^^^ required by this bound in `needs_send`
help: `Send` can be made part of the associated future's guarantees for all implementations of `Foo::test`
   |
LL -     async fn test() -> () {}
LL +     fn test() -> impl std::future::Future<Output = ()> + Send { async {} }
   |

error[E0277]: `impl Future<Output = i32>` cannot be sent between threads safely
  --> $DIR/send-on-async-fn-in-trait.rs:15:16
   |
LL |     needs_send(T::test2());
   |     ---------- ^^^^^^^^^^ `impl Future<Output = i32>` cannot be sent between threads safely
   |     |
   |     required by a bound introduced by this call
   |
   = help: the trait `Send` is not implemented for `impl Future<Output = i32>`
note: required by a bound in `needs_send`
  --> $DIR/send-on-async-fn-in-trait.rs:12:27
   |
LL |     fn needs_send(_: impl Send) {}
   |                           ^^^^ required by this bound in `needs_send`
help: `Send` can be made part of the associated future's guarantees for all implementations of `Foo::test2`
   |
LL -     async fn test2() -> i32 { 1 + 2 }
LL +     fn test2() -> impl std::future::Future<Output = i32> + Send {async { 1 + 2 } }
   |

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.