1 error: future cannot be sent between threads safely
2 --> $DIR/issue-64130-non-send-future-diags.rs:23:13
5 | ^^^^^ future returned by `foo` is not `Send`
7 = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `MutexGuard<'_, u32>`
8 note: future is not `Send` as this value is used across an await
9 --> $DIR/issue-64130-non-send-future-diags.rs:17:10
11 LL | let g = x.lock().unwrap();
12 | - has type `MutexGuard<'_, u32>` which is not `Send`
14 | ^^^^^^ await occurs here, with `g` maybe used later
16 | - `g` is later dropped here
17 note: required by a bound in `is_send`
18 --> $DIR/issue-64130-non-send-future-diags.rs:9:15
20 LL | fn is_send<T: Send>(t: T) { }
21 | ^^^^ required by this bound in `is_send`
23 error: aborting due to previous error