error[E0277]: `dyn Future<Output = ()> + Send` cannot be shared between threads safely
  --> tests/ui/arg_not_sync.rs:13:20
   |
13 |     assert_is_sync(send_not_sync());
   |     -------------- ^^^^^^^^^^^^^^^ `dyn Future<Output = ()> + Send` cannot be shared between threads safely
   |     |
   |     required by a bound introduced by this call
   |
   = help: the trait `Sync` is not implemented for `dyn Future<Output = ()> + Send`, which is required by `Pin<Box<dyn Future<Output = ()> + Send>>: Sync`
   = note: required for `Unique<dyn Future<Output = ()> + Send>` to implement `Sync`
note: required because it appears within the type `Box<dyn Future<Output = ()> + Send>`
  --> $RUST/alloc/src/boxed.rs
   |
   | pub struct Box<
   |            ^^^
note: required because it appears within the type `Pin<Box<dyn Future<Output = ()> + Send>>`
  --> $RUST/core/src/pin.rs
   |
   | pub struct Pin<Ptr> {
   |            ^^^
note: required by a bound in `assert_is_sync`
  --> tests/ui/arg_not_sync.rs:3:27
   |
3  | fn assert_is_sync(_: impl Sync) {}
   |                           ^^^^ required by this bound in `assert_is_sync`

error[E0277]: `dyn Future<Output = ()>` cannot be shared between threads safely
  --> tests/ui/arg_not_sync.rs:14:20
   |
14 |     assert_is_sync(not_send_not_sync());
   |     -------------- ^^^^^^^^^^^^^^^^^^^ `dyn Future<Output = ()>` cannot be shared between threads safely
   |     |
   |     required by a bound introduced by this call
   |
   = help: the trait `Sync` is not implemented for `dyn Future<Output = ()>`, which is required by `Pin<Box<dyn Future<Output = ()>>>: Sync`
   = note: required for `Unique<dyn Future<Output = ()>>` to implement `Sync`
note: required because it appears within the type `Box<dyn Future<Output = ()>>`
  --> $RUST/alloc/src/boxed.rs
   |
   | pub struct Box<
   |            ^^^
note: required because it appears within the type `Pin<Box<dyn Future<Output = ()>>>`
  --> $RUST/core/src/pin.rs
   |
   | pub struct Pin<Ptr> {
   |            ^^^
note: required by a bound in `assert_is_sync`
  --> tests/ui/arg_not_sync.rs:3:27
   |
3  | fn assert_is_sync(_: impl Sync) {}
   |                           ^^^^ required by this bound in `assert_is_sync`