error: coroutine cannot be sent between threads safely
  --> $DIR/ref-upvar-not-send.rs:15:30
   |
LL |       assert_send(#[coroutine] move || {
   |  ______________________________^
LL | |
LL | |
LL | |         yield;
LL | |         let _x = x;
LL | |     });
   | |_____^ coroutine is not `Send`
   |
   = help: the trait `Sync` is not implemented for `*mut ()`
note: captured value is not `Send` because `&` references cannot be sent unless their referent is `Sync`
  --> $DIR/ref-upvar-not-send.rs:19:18
   |
LL |         let _x = x;
   |                  ^ has type `&*mut ()` which is not `Send`, because `*mut ()` is not `Sync`
note: required by a bound in `assert_send`
  --> $DIR/ref-upvar-not-send.rs:6:19
   |
LL | fn assert_send<T: Send>(_: T) {}
   |                   ^^^^ required by this bound in `assert_send`

error: coroutine cannot be sent between threads safely
  --> $DIR/ref-upvar-not-send.rs:23:30
   |
LL |       assert_send(#[coroutine] move || {
   |  ______________________________^
LL | |
LL | |
LL | |         yield;
LL | |         let _y = y;
LL | |     });
   | |_____^ coroutine is not `Send`
   |
   = help: within `{coroutine@$DIR/ref-upvar-not-send.rs:23:30: 23:37}`, the trait `Send` is not implemented for `*mut ()`
note: captured value is not `Send` because `&mut` references cannot be sent unless their referent is `Send`
  --> $DIR/ref-upvar-not-send.rs:27:18
   |
LL |         let _y = y;
   |                  ^ has type `&mut *mut ()` which is not `Send`, because `*mut ()` is not `Send`
note: required by a bound in `assert_send`
  --> $DIR/ref-upvar-not-send.rs:6:19
   |
LL | fn assert_send<T: Send>(_: T) {}
   |                   ^^^^ required by this bound in `assert_send`

error: aborting due to 2 previous errors