async/await: improve obligation errors

This commit improves obligation errors for async/await:

```
note: future does not implement `std::marker::Send` because this value is used across an
      await
  --> $DIR/issue-64130-non-send-future-diags.rs:15:5
   |
LL |     let g = x.lock().unwrap();
   |         - has type `std::sync::MutexGuard<'_, u32>`
LL |     baz().await;
   |     ^^^^^^^^^^^ await occurs here, with `g` maybe used later
LL | }
   | - `g` is later dropped here
```

Signed-off-by: David Wood <david@davidtw.co>

0 files changed, 0 insertions, 0 deletions