error: future cannot be sent between threads safely --> $DIR/issue-68112.rs:37:5 | LL | require_send(send_fut); | ^^^^^^^^^^^^ future created by async block is not `Send` | = help: the trait `Sync` is not implemented for `RefCell<i32>` = note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead note: future is not `Send` as it awaits another future which is not `Send` --> $DIR/issue-68112.rs:34:17 | LL | let _ = non_send_fut.await; | ^^^^^^^^^^^^ await occurs here on type `impl Future<Output = Arc<RefCell<i32>>>`, which is not `Send` note: required by a bound in `require_send` --> $DIR/issue-68112.rs:14:25 | LL | fn require_send(_: impl Send) {} | ^^^^ required by this bound in `require_send` error: future cannot be sent between threads safely --> $DIR/issue-68112.rs:46:5 | LL | require_send(send_fut); | ^^^^^^^^^^^^ future created by async block is not `Send` | = help: the trait `Sync` is not implemented for `RefCell<i32>` = note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead note: future is not `Send` as it awaits another future which is not `Send` --> $DIR/issue-68112.rs:43:17 | LL | let _ = make_non_send_future1().await; | ^^^^^^^^^^^^^^^^^^^^^^^ await occurs here on type `impl Future<Output = Arc<RefCell<i32>>>`, which is not `Send` note: required by a bound in `require_send` --> $DIR/issue-68112.rs:14:25 | LL | fn require_send(_: impl Send) {} | ^^^^ required by this bound in `require_send` error[E0277]: `RefCell<i32>` cannot be shared between threads safely --> $DIR/issue-68112.rs:65:5 | LL | require_send(send_fut); | ^^^^^^^^^^^^ `RefCell<i32>` cannot be shared between threads safely | = help: the trait `Sync` is not implemented for `RefCell<i32>` = note: if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead = note: required for `Arc<RefCell<i32>>` to implement `Send` note: required because it's used within this `async fn` body --> $DIR/issue-68112.rs:50:31 | LL | async fn ready2<T>(t: T) -> T { | _______________________________^ LL | | t LL | | } | |_^ note: required because it appears within the type `impl Future<Output = Arc<RefCell<i32>>>` --> $DIR/issue-68112.rs:53:31 | LL | fn make_non_send_future2() -> impl Future<Output = Arc<RefCell<i32>>> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ = note: required because it captures the following types: `impl Future<Output = Arc<RefCell<i32>>>`, `Ready<i32>` note: required because it's used within this `async` block --> $DIR/issue-68112.rs:60:20 | LL | let send_fut = async { | ____________________^ LL | | let non_send_fut = make_non_send_future2(); LL | | let _ = non_send_fut.await; LL | | ready(0).await; LL | | }; | |_____^ note: required by a bound in `require_send` --> $DIR/issue-68112.rs:14:25 | LL | fn require_send(_: impl Send) {} | ^^^^ required by this bound in `require_send` error: aborting due to 3 previous errors For more information about this error, try `rustc --explain E0277`.